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20th International Conference on Design Theory and Methodology (DTM)

2008;():3-9. doi:10.1115/DETC2008-49276.

Designers have been known to seek analogical inspiration during design ideation. This paper presents an experiment that studies the types of analogies that most impact design creativity, as well as the time during problem solving when it is most effective to seek such analogical stimulation. This experiment showed that new information that was highly similar to the problem affected problem solving even if the information was given before problem solving began. On the other hand, new information that was distantly related to the problem only affected problem solving when it was presented during a break after problem solving had already begun. These results support the idea that open goals increase the likelihood that distantly related information become incorporated into problem solving. Functional principles found in the problem-relevant information given were also found to prime solutions in corresponding categories.

Commentary by Dr. Valentin Fuster
2008;():11-19. doi:10.1115/DETC2008-49293.

This paper describes a study to understand the use of analogies by design engineers with different levels of experience. Protocol analyses of twelve design engineers have been analysed to understand the functions and reasoning of the analogies. The protocols are real world data from the aerospace industry. The findings indicate a significant difference in both the functions and reasoning by novices and experienced designers. Novices were found to predominantly transfer information without explicit reference to design issues, whereas experienced designers tended to either solve or identify problems. Experienced designers were found to reason about the function of a component and to some degree the predicted behaviour of the component, whereas the novices seem to lack such reasoning processes.

Topics: Engineers , Design
Commentary by Dr. Valentin Fuster
2008;():21-32. doi:10.1115/DETC2008-49317.

Numerous examples of innovation through analogy are found throughout current trade journals, magazines and product offerings. Design-by-analogy is a powerful tool in creative design, but generally relies on unproven, ad-hoc approaches. Although a few notable computational knowledge bases have been created to support analogous design, very few methods provide suitable guidance on how to identify analogies and analogous domains. This paper presents a novel approach, referred to as the WordTree Design-by-Analogy Method, for identifying analogies as part of the ideation process. The WordTree Method derives its effectiveness through a design team’s knowledge and readily available information sources but does not require specialized computational knowledge bases. A controlled experiment and an evaluation of the method with redesign projects illustrate the method’s influence in assisting engineers in design-by-analogy. Unexpected and unique solutions are identified using the method. The experimental results also highlight potential improvements for the method and areas for future research in engineering design theory.

Topics: Design , Innovation
Commentary by Dr. Valentin Fuster
2008;():33-44. doi:10.1115/DETC2008-49331.

Metaphors have successfully been used by new product development and design teams to help frame the design situation and communicate new products to stakeholders. Yet, the process of finding a compelling metaphor often turns upon stumbling upon it or a flash of insight from a team member. We present Meta4acle: a Metaphor Exploration Tool for design that suggests possible metaphors to make the process more one of ‘seeking out’ than ‘stumbling upon’ an effective metaphor. The tool takes data about the project in the form of a title, domain and key associations required of the metaphor and returns suggestions from a database of possible metaphor sources. We built a Meta4acle prototype and evaluated it with positive results for three existing design case studies. We present plans for its full implementation and evaluation.

Topics: Design
Commentary by Dr. Valentin Fuster
2008;():45-53. doi:10.1115/DETC2008-49023.

Design Structure Matrix (DSM) is known as an efficient tool to modularize product architectures. It is only effective when all the matrix elements are described with a similar level of abstraction. This lies generally in the level of the real existing components. In order to implement a DSM, all assemblies, components and their relations have to be defined beforehand. In this step, the product architecture is often developed intuitively without any analysis. After the analysis using DSM, the developed product architecture normally requires rectification. Some components have to be designed and modified repeatedly. In this paper, the model for describing the relationship between function and embodiment, the Contact and Channel Model (C&CM) as well as an approach and its implementation will be presented to avoid this repetition. After a principle solution has been selected, the system is modeled with C&CM elements in a new intermediate level of abstraction. An integration analysis by DSM can be performed in parallel with the use of a search algorithm to find the modular product architecture. The analysis result is a guideline for a modular architecture which helps designers to reduce the number of required iterations. This approach is implemented in the development of a robot forearm for the humanoid robot ARMAR III.

Commentary by Dr. Valentin Fuster
2008;():55-66. doi:10.1115/DETC2008-49526.

The utilization of a platform strategy has become a competitive priority in many industries, most notably in the automotive industry. Naturally, many firms in other industries are adopting this strategy with different modifications and degrees of implementation. However, little research covers the application of platform development in a supplier and/or small batch production environment. The adaptation of a platform strategy in these settings, by a supplier in the aircraft engine industry, is the focal point of this paper. Based on platform development literature and the characteristics of the aircraft engine industry and the company studied advantages and hindrances for platform strategies have been ruled out. Interviews with involved people within the company studied have further clarified different perspectives on platforms and their possible utilization. Based on the analysis of collected information it is proposed that a possible platform strategy would include: a technology platform, incorporating general knowledge on core technology assets embodied in either humans, organizations, processes, information or methods; and a product platform, incorporating product specific elements that could be re-used when developing new components for a particular product line.

Commentary by Dr. Valentin Fuster
2008;():67-76. doi:10.1115/DETC2008-49815.

Development of product families involves an interplay of common and differentiating features to address market segments. Considerable research has been conducted by the engineering community to support the development of product families from a product characteristic viewpoint. However, differences in consumable products are not often easily identified so they rely more heavily on the packaging to differentiate to market segments. Metrics, indices and representations have been formulated to support considerations of commonality and differentiation of engineered products. This paper describes the potential for similar approaches to benefit the features of packaging, particularly medication packaging. The potential benefit of such approaches reach beyond marketing and sales. There is a considerable opportunity for improving dispensing of medications because packaging confusion has been recognized as a serious problem, where misidentification can be lethal. With tens of thousands of drug varieties and growing, a packaging metric is necessary. This paper presents a proposed metric along with three supporting case studies.

Topics: Drugs , Packaging
Commentary by Dr. Valentin Fuster
2008;():77-86. doi:10.1115/DETC2008-49901.

The growth rate of R&D activities in automotive industry brings an increased need for transfer of design knowledge. This, in combination with growing complexity of the product puts new demands on the decision process. In this paper, decision methods used within the R&D department of an international vehicle manufacturer has been investigated through interviews and surveys. The main focus has been to identify and analyze methods used by the individual roles within different development teams. The survey reveals that a majority of the respondents use unstructured methods for resolving decision issues. When respondents were asked about their preferences there was an expressed need for more structured methods. Among these, two methods are elaborated that are well established within the product development process: expert support and guidelines, but also on methods training in general. A third conclusion is to redirect the current decision process to build on more structured methods through training. This work has contributed also by identifying the company best practice. The long term goal is to have all development teams adopt one common development process at the team level.

Commentary by Dr. Valentin Fuster
2008;():87-96. doi:10.1115/DETC2008-49905.

This article discusses the resource utilization of embedded systems in the automotive industry. Traditionally, the major cost driver — or resource input — has been regarded as the hardware cost. Issues such as software development costs and maintenance costs have historically been neglected. In order to address this, the article embraces the more comprehensive view on resources that a resource can be regarded as anything which could be thought of as a strength or weakness of a given firm. In this article the major drivers of resource consumption are identified. The work has also included several interviews with employees in order to find empirical data of the embedded systems in vehicles. This paper proposes a method to evaluate the resource efficiency of user functions implemented through the embedded system. By the use of Data Envelopment Analysis — which has proven to be a useful method — the resource utilization of six user functions is evaluated. Future work of particular interest would be to perform a more extensive case study.

Commentary by Dr. Valentin Fuster
2008;():97-106. doi:10.1115/DETC2008-49147.

This paper presents a knowledge-lean learning and inference mechanism based on Singular Value Decomposition (SVD) for design optimization problem (re)-formulation at the problem modeling stage. The distinguishing feature of the mechanism is that it requires very few training cases to extract and generalize knowledge for large classes of problems sharing similar characteristics. The genesis of the mechanism is based on viewing problem (re)-formulation as a statistical pattern extraction problem. SVD is applied as a dimensionality reduction tool to extract semantic patterns from a syntactic formulation of the design problem. We explain and evaluate the mechanism on a model-based decomposition problem, a hydraulic cylinder design problem, and a medium-large scale Aircraft Concept Sizing problem. The results show that the method generalizes quickly and can be used to impute relations between variables, parameters, objective functions, and constraints when training data is provided in symbolic analytical form, and is likely to be extensible to forms when the representation is not in analytical functional form.

Commentary by Dr. Valentin Fuster
2008;():107-118. doi:10.1115/DETC2008-49366.

Shape grammars provide the means to represent the physical embodiment of a class of products in a set of generative rules. Once developed, the shape grammar can be used to generate new forms through automated synthesis or interaction by one or more designers. However, a fundamental shortcoming of this rule-based system is that creating the shape rules is time consuming and imprecise. The traditional approach to create a set of rules from an existing set of products was an ad hoc process of generalizing form, identifying feature options, and classifying logical subdivisions of the complete product geometry. This paper proposes a formal method of shape grammar creation that is aligned with well-known design methodologies and tools in order to enable the creation of a shape grammar during the product development process. The established methodologies for creating functional models and modular products provide many of the requisite steps for creating a shape grammar and provide a skeleton onto which a rule creation approach can be mapped.

Topics: Design , Shapes
Commentary by Dr. Valentin Fuster
2008;():119-127. doi:10.1115/DETC2008-49853.

This paper discusses a new topological optimization technique to solve graph based engineering design problems by decoupling parameters and topology changes. Using this approach optimal solutions are synthesized in the form of graph topologies for engineering problems. Currently we have successfully applied it to routing problems, resistive networks, neural networks, and sheet metal. This final problem has proven the most challenging but the results are not only novel and manufacturable but also satisfy multiple objective functions such as material cost and manufacturability. This paper presents Topological and Parametric Tune and Prune (TP2 ) as the first topology optimization method that has been developed specifically for domains representable by a graph grammar schema. The method is stochastic and incorporates distinct phases for modifying the topologies and modifying parameters stored within topologies. Thus far, with the problems that been tested, (TP2 ) had proven better than genetic algorithm in terms of the quality of solutions and time taken to acquire them.

Topics: Design , Optimization
Commentary by Dr. Valentin Fuster
2008;():129-136. doi:10.1115/DETC2008-50102.

The method presented in this note mimics two fundamental mechanisms from nature, growth, and development, for the synthesis of new three-dimensional structures. The structures were synthesized to support a load generated by a wind. Every structure grows from a single artificial cell following a set of genes, encoded in an artificial genome shared by all cells. Genes are a set of commands that control the growth process. Genes are regulated by interaction with the environment. The environment is both external and internal to the structure. The performance each structure is measured by its ability to hold the load and other additional engineering criteria. A population of structures is evolved using a genetic algorithm, which alters the genome of two mating individuals. We will present evolved phenotypes with high degrees of modularity and symmetry which evolved according to engineering criteria. Neither one of these two characteristics has been directly imposed as the fitness evaluation, but rather spontaneously emerge as a consequence of natural selection. We will argue that the types of rules we are using in this model are not biased toward any of these characteristics, but rather basic rules for growth and development.

Commentary by Dr. Valentin Fuster
2008;():137-148. doi:10.1115/DETC2008-49363.

Biology has long been recognized as an excellent source of analogies and stimuli for engineering design. Previous work focused on the systematic identification of relevant biological analogies by searching for instances of functional keywords in biological information in natural language format. This past work revealed that engineering keywords couldn’t always be used to identify the most relevant biological analogies, as the vocabularies between biology and engineering are sufficiently distinct. Therefore, a method of identifying biologically meaningful keywords that correspond to engineering keywords was developed. Here, we apply and refine this method by generating biologically meaningful keywords for the terms of the Functional Basis, which is widely accepted as a standardized representation of the functionality of engineering products. We present insights gained on the selection of biologically meaningful keywords for the function sets based on semantic relations. We then observe the use of our keywords by providing 4th year undergraduate design students with the biologically meaningful keywords that are related to the desired functions of their design projects.

Commentary by Dr. Valentin Fuster
2008;():149-159. doi:10.1115/DETC2008-49372.

The relationship between language and reasoning motivates us to study the use of language within engineering design. This paper describes our continued investigation of language as stimuli for concept generation. Specifically we investigate dichotomous lexical stimuli that are related to the problem in either a disagreeing, incongruent manner or in an agreeing, congruent manner. This is a follow-up investigation where we extend previous experiments to include both congruent and incongruent stimuli to enable comparison of differences between designer behavior and concepts. A between-subjects think-aloud experiment was performed where participants were presented with a problem and asked to generate concepts to address the problem. Half the participants were provided with incongruent stimuli and the remaining were provided with congruent stimuli. Participants provided with incongruent stimuli used the stimulus words as verbs more often than the participants provided with congruent stimuli. Verbs possess several properties desirable for use as design stimuli including the increased introduction of new lexicalized concepts to the concept generation process. When two independent raters scored the concepts, there was a positive correlation between the raters that concepts developed with incongruent stimuli were more novel. Understanding the effects of different lexical stimulus types on concept generation contributes to the development of design support tools that exploit the relationship between language and reasoning to increase design novelty.

Commentary by Dr. Valentin Fuster
2008;():161-170. doi:10.1115/DETC2008-49672.

When retrospectively analyzing the design process of a creative product, the creative leap or moment of inspiration is often described by the designer in an ‘idealized way’ [1]. There is little evidence within literature describing when the ideas behind promising concepts were conceived. This study tracks several real industrial design projects in the early conceptual design phase. The development and manipulation of ideas captured during the initial group brainstorm meeting are assessed in terms of the concepts at the following stage gate meeting. In addition, several different forms of stimulus were introduced to the different groups and compared to a control group. The results showed that the frequency of idea production remained virtually constant for the first 60 minutes. However, the number of ideas to form part of a concept at the stage gate meeting dropped markedly after the first 20 minutes. The frequency of appropriate ideas featuring within stage gate concepts increased with the introduction of stimuli, highlighting the positive effect of introducing stimuli.

Commentary by Dr. Valentin Fuster
2008;():171-182. doi:10.1115/DETC2008-50035.

This paper proposes a new model for the creative process of design. This model is developed by combining two of the most accepted models of creativity: the Wallas stage model and the Wertheimer productive thinking model. The paper discusses the importance of Biomimetics in design and presents examples of successful inventions produced when nature is imitated by designers. The role of Biomimetics in the new model for the creative process is discussed. For complementing the new model of creativity, this paper introduces the concept of Artiomimetics as the imitation of artifact structure, shape, features or motion to inspire the development of new inventions. This paper proposes that the incremental evolution of concepts that lead to invention is given by either the application of Biomimetics or Artiomimetics. This paper presents examples where the duality of biomimetic and artiomimetic approaches is used to effectively foster creativity resulting in breakthrough inventions.

Topics: Design , Biomimetics
Commentary by Dr. Valentin Fuster
2008;():183-192. doi:10.1115/DETC2008-49373.

Since its birth from the Design Automation Conference (DAC) and the Association for the Advancement of Artificial Intelligence (AAAI) twenty years ago, the Design Theory and Methodology (DTM) Conference has accepted 769 papers for presentation in a total of 179 tracks. Papers have covered advances in design theory and methods as well as design education, decision making, product development, collaborative endeavors, case studies, information processing, computational methods and industrial applications. Through the years tracks have evolved to better define existing research topics and branched to spawn new areas of interest. This paper presents a retrospective of the past twenty years of the DTM conference including a look at the evolution of tracks, those researchers who have contributed and predictions for the upcoming twenty years.

Topics: Design theory
Commentary by Dr. Valentin Fuster
2008;():193-202. doi:10.1115/DETC2008-49338.

Adaptable products are gaining interests. Those products are able to adapt themselves to new environments, new states or new user defined tasks. There is not yet a standard design methodology for designing those products. This paper focuses on making large complex products (e.g. printers) more adaptable. Large-scale complex systems need to have modular architecture to some extent in order for engineers to be able to clearly comprehend the product. Therefore, a method to cluster components of an adaptable system is developed based on Design Structure Matrix (DSM) which stores information about connections between components. For each scenario or action plan to perform adaptability, the importance of component interconnections is rated in a separate DSM structure. By combining the original DSM with the adaptability DSM the engineers can group components. Finally, an example of a coffee maker is illustrated.

Commentary by Dr. Valentin Fuster
2008;():203-216. doi:10.1115/DETC2008-49343.

With the increasing stratification of customer preferences, companies must offer a number of options to remain competitive. Current methodologies, such as product families, seek to offer more options to the consumer while minimizing costs to the company. Customizable products are striving to offer the customer what they truly desire by increasing the level of influence the consumer has on their instance of the design. As the shift from cosmetic changes and modular options continues, systems will be required to have a greater amount of design flexibility to allow for the changes made by individual consumers. Drawing on reconfigurable system and product family research, metrics for flexibility are proposed for use in the early stages of the design process. Discussion focuses on functional aspects of a product which affect flexibility and the rational behind the component metrics representing their flexibility. The goal of the metrics is to assist with the evaluation of design options by rating the overall flexibility of the system early in the design process. A case study is presented to demonstrate the use of the metrics.

Topics: Plasticity , Design
Commentary by Dr. Valentin Fuster
2008;():217-230. doi:10.1115/DETC2008-49370.

A product’s flexibility for future evolution is its ability to be quickly and economically adapted to meet changing requirements. In previous work, a set of guidelines has been developed for designing flexible products. In this paper, two similar industrial case studies are presented to investigate the effectiveness of these guidelines for designing small-lot products with flexibility for future evolution. The systems are real products that have been designed and built by the authors, providing unrestricted insight into the design process and outcome of each project. The first product, a large testing system for high pressure seals, was designed without the aid of flexibility for future evolution guidelines. The second product, an automated welding test station, was designed with flexibility for future evolution as a specific deliverable of the final product. The flexibility of each system was measured by considering its adaptability to prototypical change modes. Of the two systems, the welding system was found to be more flexible than the seal testing system. The welding system also served as an example of integrating product flexibility guidelines throughout the development process.

Topics: Plasticity , Design
Commentary by Dr. Valentin Fuster
2008;():231-244. doi:10.1115/DETC2008-49406.

Design for multiple product lifecycles with component reuse potentially improves profitability, customer satisfaction and environmental impact. However, deciding on the scope and the level of detail (granularity) to be considered in the design process can be challenging. Although a comprehensive model that takes into account all important issues would be immensely useful, modeling difficulties and computational intractability prevent their successful implementation. This paper extends the scope of a previously developed design decision tool for determining optimal end-of-lifecycle decisions. The single product case is extended to a product portfolio, which has been shown to capture more demand. Demand is explicitly considered and its modeling is accomplished with the use of copulas. An important result from statistics, Sklar’s theorem, provides a way to use data from existing product sales to estimate demand for currently nonexistent reused products. In addition, effective age calculations are updated. On the computational front, time-continuation and seeding is used for NSGA-II to converge to optima more quickly in the resulting larger problem. A personal computer case study illustrates the effect of different parameters such as portfolio size, the possibility of recycle, and limits on environmental impact (as opposed to mandated take-back).

Topics: Design
Commentary by Dr. Valentin Fuster
2008;():245-254. doi:10.1115/DETC2008-49315.

This paper presents a novel indirect matching approach between the function layer and the form layer to enhance the capability for the FBS method to obtain the creative conceptual design results. Firstly, the basic operation actions set, which is composed of the basic operation actions obtained by decomposing each function in the lowest level of the function decomposition tree in the FBS model into the sub-functions, in the function layer is regrouped dynamically. This behavior regroup process has introduced the new design variables into the conceptual design process and leads the behavior creativity to produce. On the other hand, considering the multi-functions for each basic structure to have and representing these functions with the basic operation actions, then the basic operation actions set in the form layer is set up. Dynamic regrouping this set in the form layer, the new design variables has been introduced into the conceptual design process, and leads the form creativity to produce. Through the above behavior-form double directions creative process, the solution scope of the conceptual design is enlarged obviously. Therefore, the method present in this paper has enough capability to obtain the creative conceptual results. Furthermore, the model presented in this paper is represented with the quotient space mathematically. The case study has shown that in the function layer, through adjusting the attribute function, which determines the partition grain of the basic operation actions set in the function layer or in the form layer, the new behaviors can be generated.

Commentary by Dr. Valentin Fuster
2008;():255-263. doi:10.1115/DETC2008-49342.

In this paper I consider the relations between the different meanings and representations of the concept of technical function that are in use in engineering design methodology. I focus on two representation schemes — the verb-noun and the operation-on-flows representations — and analyse whether representations of technical functions created with the one scheme can be transposed into representations of the same functions with the other scheme. I argue that the answer depends on the particular meaning of function that one adopts. When functions of technical systems refer to behaviours of those systems, then the two representations can be reciprocally transposed following the rule that the verbs in the verb-noun representations correspond to the operations in the operation-on-flows representations, and the nouns to the (main) flows. When, however, technical functions refer to the purposes for which systems are designed, it can be argued that these representations cannot be transposed using this rule. The reason for this result is that operation-on-flows combinations, where the flows are flows through technical systems, are, in general, not suited to represent purposive technical functions of the systems. In a subsidiary and more explorative discussion I focus on the transposition of verb-noun representations of purposive functions into operation-on-flows representations of behavioural functions in design methodologies such as the Functional Basis account of Robert Stone and Kristin Wood.

Topics: Functions
Commentary by Dr. Valentin Fuster
2008;():265-272. doi:10.1115/DETC2008-49349.

Component functional templates are a foundational tool, for the functional modeling method, that novice users can implement to develop functional modeling skills and produce better results by not requiring the modeler to have extensive background knowledge in the method. The templates provide common function layouts of ordinary electromechanical components that are based on historic data collected from design information on a wide range of consumer products. A previous experiment has been performed on a sophomore level design class to assess the change in quality between functional modeling results with and without the use of component functional templates. To address further evaluation of the usefulness the templates, another experiment was performed on multiple sections of an undergraduate engineering design course, controlling the amount of time that the students are exposed to the templates, in order to eliminate any extended exposure biases in the models using the templates. Quality and accuracy of the resulting models were gauged using a metric consisting of function structure, number of functions, flow representation through a chain, and product representation (the same metric used in the previous experiment). The results show that the students using the component functional templates consistently made fewer mistakes in their models in all categories than those that did not use them and thus, produced better models in terms of quality and accuracy.

Commentary by Dr. Valentin Fuster
2008;():273-286. doi:10.1115/DETC2008-49369.

Functional models are representations of the energy, material and signal transformations that occur through the expected or normal operating condition of a product. As the complexity of products increases, there are often multiple dimensions to their operation in addition to their nominal operating state, e.g., crash protection systems in a car or laser leveling and stud finding combined in a single tool. Here system state is used to represent the different operational dimensions of a product, and a representation scheme that allows designers to fully explore system functionality of products with multiple system states is explored. Previous work in process and functional analysis is integrated to better represent complex systems with multi-dimensional system functionality. Process and functional modeling are integrated to produce a new function design framework supporting user-defined fidelity of hierarchical models for functional representation. An example modeling a complete automobile life cycle illustrates the development of integrated process and functional models within a complex system analysis.

Commentary by Dr. Valentin Fuster
2008;():287-296. doi:10.1115/DETC2008-49140.

As the content and variety of technology increases in automobiles, the complexity of the system increases as well. Decomposing systems into modules is one of the ways to manage and reduce system complexity. This paper surveys and compares a number of state-of-art components modularity metrics, using 8 sample test systems. The metrics include Whitney Index (WI), Change Cost (CC), Singular value Modularity Index (SMI), Visibility-Dependency (VD) plot, and social network centrality measures (degree, distance, bridging). The investigation reveals that WI and CC form a good pair of metrics that can be used to assess component modularity of a system. The social network centrality metrics are useful in identifying areas of architecture improvements for a system. These metrics were further applied to two actual vehicle embedded software systems. The first system is going through an architecture transformation. The metrics from the old system revealed the need for the improvements. The second system was recently architected, and the metrics values showed the quality of the architecture as well as areas for further improvements.

Commentary by Dr. Valentin Fuster
2008;():297-307. doi:10.1115/DETC2008-49860.

Many product manufacturing companies in today’s environment constantly need to develop new technologies and infuse them into their line of products to stay ahead of the competition. Most new technologies only deliver value once they are successfully infused into a parent system. However, there has been very little research done to develop formal methodologies to assess the impact and implication of new technology infusion into existing products. In this paper, a systematic process framework to quantify and assess the impact of technology infusion early in the product planning cycle is proposed. The proposed methodology quantitatively estimates the impact of technology infusion through the use of a Design Structure Matrix (DSM) and the creation of a Delta DSM (ΔDSM) describing the changes to the original system based on the infused technology. The cost for technology infusion is then estimated from the ΔDSM, and the market impact of the technology is calculated using customer value (utility) curves for customer relevant system performance measures. Finally, the probabilistic ΔNPV of a newly infused technology is obtained using Monte Carlo simulation. The proposed methodology was demonstrated on a complex printing system, represented as an 84 element DSM with a density of 3.7%, where a newly developed value enhancing technology was infused into the existing product. The result shows that a positive marginal net present value ΔNPV can be expected, despite the new technology causing an invasiveness of 8.5% to the existing design. The methodology can be applied in a rigorous and repeatable manner, opening up possibilities for further implementation of the proposed framework, including analysis of the interactions amongst technologies.

Commentary by Dr. Valentin Fuster
2008;():309-321. doi:10.1115/DETC2008-49963.

An appropriate modularity representation is of critical importance in modular design. Without an appropriate representation, modular design cannot realize its benefits. In this paper, a representation for DSM-based modular product design is developed that facilitates product modularization with respect to the design process. The representation is based upon previous work presented in this venue that details representations for the assembly and manufacturing processes (Lai and Gershenson, 2007a; Lai and Gershenson, 2007b). The representation for the design process includes a design process similarity matrix and a design process dependency matrix. The definition of design process similarity uses information available in early stage design and is based on the similarity of the design tools and resources required for later stage design. Design process similarity within a module leads to increased design efficiency from the sharing of functional and geometric analyses and possibly the savings of not needing to “un-immerse” from a particular design task to “re-immerse” in the design of the next component. The definition of design process dependency is based on the connectivity caused by components’ design process attributes with the goal of fewer design interactions between different modules. With zero dependencies between modules, we hope to contain the cascade of design changes within each module, and prevent the need to redesign other modules. In this paper, we first present which design process elements we should consider for defining design process similarity and dependency, and then construct respective similarity and dependency factors tables. These tables include similarity and dependency factors, which, along with their values, are important in determining a product’s modular architecture at the early stages of design. Finally, a computer mouse is used to illustrate how to apply these factors tables to generate the similarity and dependency matrices that represent product modularity for the product design process. Using these representations as input to the DSM-based modular design methods, we can achieve a design with a modular architecture that improves design efficiency in the later stages of design. In the future, we hope to extend and generalize the process for developing product modularity representations so that it is applicable across all life-cycle processes.

Topics: Design
Commentary by Dr. Valentin Fuster
2008;():323-332. doi:10.1115/DETC2008-50064.

In today’s product development environment, most companies develop product platforms rather than individual products due to the time and cost savings that are reaped from subsequent development efforts. Most of the product platform development literature focuses on the development decisions for a product platform while it is under development, which is logically where the biggest benefits would be gained. However when a new market or a new technology arises, firms often struggle to assess these opportunities within the context of their existing product platforms. There is relatively little work that examines the product platform decisions after the platform has been developed and new, unanticipated opportunities are presented to the development organization. The focus of this work is to leverage the existing literature to development an impact assessment process that explicitly accounts for the constraints of a preexisting product platform when considering new technology and/or market opportunities. In this paper, an overview of the overall assessment process is presented. This is followed by the development of the impact metrics and a case study to illustrate the assessment process. The paper concludes with the next step in this work.

Commentary by Dr. Valentin Fuster
2008;():333-342. doi:10.1115/DETC2008-49116.

Managing design freezes plays an important part in today’s competitive markets and successful freeze management can make the difference between delivering a product in time and in budget or failed design projects. On the one hand, design managers want to limit change propagation by freezing components or component-interfaces in order to avoid unwanted change propagation and to meet design lead-times. On the other hand freezing the design of a component too early can constrain innovation and having to unfreeze a design that was frozen before can add further redesign costs. This paper introduces an algorithm for determining an optimal change freeze order (CFO) based on combined change risks and component redesign cost, which has been applied in an automotive company in the design of a diesel engine.

Commentary by Dr. Valentin Fuster
2008;():343-353. doi:10.1115/DETC2008-49380.

Specifying the product platform and family architecture to support product varieties can be a challenging task for companies. Especially when various viewpoints have to be considered which include product variety, materials, manufacturing complexity, assembly complexity, average component count commonality, assembly sequence and late point differentiation. Consequently there is a need for reasoning to balance multiple viewpoints in the case of product families for the development of good architecture. In this paper we present a product family architecture design approach that can be applied to develop efficient product family architectures for a given set of product functions, while considering multiple viewpoints. In order to identify the efficient product family architecture(s) a three phase approach is presented: (1) Generating a set of feasible module architectures of options for each product function; (2) Combining the feasible module architectures and evaluating the product family architectures to identify candidate product family architectures with high evaluation scores; and (3) Improving the selected product family architecture. The product family architecture design approach is demonstrated using a coffeemaker product family.

Commentary by Dr. Valentin Fuster
2008;():355-363. doi:10.1115/DETC2008-49666.

This research work regards the development of a new roadmap for complex products design based on an improved modular approach. The goal is to refine an existing method affected by some drawbacks into a to new product development paradigm, with the aim of reducing design times, mistakes and subjectivity. The best results came from integrating a set of diverse methodologies for product design and systematic innovation. The proposed design paradigm is based on an improved Modular-TRIZ-DSM approach, and the results obtained, in terms of modules definition and interfaces, have been evaluated. The most important results concern a better repeatability of design results and the capability to forecast technical evolution of a specific product family. After a short description of the methodologies of interest, the roadmap is described focusing on the differences from the traditional method.

Commentary by Dr. Valentin Fuster
2008;():365-376. doi:10.1115/DETC2008-49713.

In product platform development the technology selection issue has seldom been studied. This article tries to fill this gap by introducing an original Technology Selection Method (TSM) to help designers to manage technology selection within the design of a product family. This method is based on technological coverage and functional verification, including the behaviour of the future product family. Practically, the proposed approach uses a multi-objective analysis based on dimensional analysis theory to choose the best technology available. The developed approach has three major points of interest. First, dimensional analysis theory is considered as a specific type of multi-objective optimisation approach which aggregates attributes using a weighting method based on the laws of physics. This manner of viewing dimensional analysis theory provides a scientific coherence to the weighting process which is not obtainable with other multi-objective methods. Second, the principle of similarity included in dimensional analysis theory is extended and allows a range of technologies and range of functions to be compared in a unique design space. Third, the dimensional analysis provides a powerful simulating tool for studying different kinds of behaviours and interactions between attributes. Consequently, dynamic aspects can be analysed and robustness analyses can be performed. The interest of such a method is highlighted through a case study involving a family of small excavators. We suggest that the potential scope of the approach is broad and our aim is to demonstrate the entire scope of the approach in future research.

Commentary by Dr. Valentin Fuster
2008;():377-385. doi:10.1115/DETC2008-49722.

This paper presents how complex system architecture lifecycles, such as that of cars, follow a similar S-curve shaped path as that of individual technological innovations. By applying this theory we show that today’s automotive industry has started a new chapter of architectural competition with similarities to its early history from 1885–1915 when steam, electric and internal combustion engine cars were competing to dominate the automotive market. Taking a historical perspective, we find that firms that organize their development activities to focus on bringing about architectural innovation are better placed in succeeding in the future market until a new dominant architecture emerges. The architecture lifecycle framework used in this study is constructed by means of a performance index. The index scores the performance of 91 cars of various architectures based on five overall system variables: power, weight, maximum velocity, fuel efficiency and the manufacturer’s suggested retail price. Depicting architectural performance over time helps identify periods of architecture competition and dominance where historical agents to change can be identified. The key factors that brought about architectural competition in the early 1900’s involved a series of innovation breakthroughs in engine and fuel technologies. Today, a new wave of power train innovations is being triggered primarily by environmental regulatory demands to reduce vehicle emissions. Future research lies in presenting a methodology for selecting vehicle architectures early on in the product development cycle that are best suited for the market going forward based on a manufacturer’s goals and a cost-benefit analysis.

Topics: Design , Automobiles
Commentary by Dr. Valentin Fuster
2008;():387-395. doi:10.1115/DETC2008-49290.

An important aspect of artifact/product design is defining the aesthetic and emotional value. The success of a product is not only dependent on it’s functionality but also on the emotional value that it creates to its user. However, if several designers are faced with a task to create an object that would evoke a certain emotion (aggressive, soft, heavy, friendly, etc.) each would most likely interpret the emotion with a different set of geometric features and shapes. In this paper the authors propose an approach to formalize the relationship between geometric information of a 3D object and the intended emotion using fuzzy logic. To achieve this; 3D objects (shapes) created by design engineering students to match a set of words/emotions were analyzed. The authors identified geometric information as inputs of the fuzzy model and developed a set of fuzzy if/then rules to map the relationships between the fuzzy sets on each input premise and the output premise. In our case the output premise of the fuzzy logic model is the level of belonging to the design context (emotion). An evaluation of how users perceived the shapes was conducted to validate the fuzzy logic model and showed a high correlation between the fuzzy logic model and user perception.

Commentary by Dr. Valentin Fuster
2008;():397-407. doi:10.1115/DETC2008-49295.

One of the greatest challenges in product development is creating a form that is attractive to an intended market audience. Functional product features are easier to test and verify through user surveys and consumer interactions. But, aesthetic preferences are as varied as the people that respond to these products. Currently, there is no technique that clearly and concisely quantifies aesthetic preference. The common methods use semantics like “strong” and “sexy”. A designer then needs to take the consumer’s desire for a certain aesthetic and translate that into a form that the consumer will find desirable. This translation is a gap in understanding that often is not crossed successfully, such as in the creation of the Pontiac Aztek. By providing the designer with a method for understanding and quantifying a consumer’s aesthetic preference for a product’s form, this gap can be closed. The designer would have concrete directions to use as a foundation for development of the product form. Additionally, the quantification of the aesthetics could be used by the designer as leverage when engineering and manufacturing decisions are made that might adversely affect the product form. This paper demonstrates how a qualitative attribute, like form, can be represented quantitatively. This quantification can be molded into a utility function which through design of experiments can be used to capture an individual’s preference for the indicated attributes. Once preference is summarized in the utility function, the utility function can be used as the basis for form generation and modification or design verification.

Commentary by Dr. Valentin Fuster
2008;():409-420. doi:10.1115/DETC2008-49383.

This paper addresses two major challenges new product development teams face in making a product people want. The first challenge is to frame the design situation based on a real need of a customer. The second challenge is to get everyone on the team in agreement about what that framing is — everyone needs to be on the same page about what it is they’re doing. Yet these two challenges are not independent, they are intertwined with each other, connected by the concrete research and sharing activities the teams perform. We introduce a framework to help understand the path of a design team along these two dimensions as well as illustrations of the three most common paths observed among graduate multidisciplinary new product development teams as supported by interviews and survey data. These case studies form the basis of four themes to help teams navigate the new product development process.

Commentary by Dr. Valentin Fuster
2008;():421-427. doi:10.1115/DETC2008-50103.

The use of design methodologies in product development has been proven to work for functional and performance requirements. However, when it comes to more abstract requirements — like attractivity — existing, widely accepted design methodologies do not provide guidance. This paper introduces tools commonly used in psychology for determining and quantifying Sensory Requirements and then proceeds to detail a method for collecting and preparing data on sensory attractiveness in a way that it is readily incorporated into the well defined method for product development, Quality Function Deployment.

Topics: Design
Commentary by Dr. Valentin Fuster
2008;():429-436. doi:10.1115/DETC2008-49266.

The conceptual design of a perfusion reactor is the subject of this paper. The main objective of the reactor is the provision of nutrients to living cells grown in a porous medium fabricated of a given ceramic foam. In order to increase reactor throughput, the nutrients should be provided in a minimum time, without affecting the cell life. Various layouts of identical ceramic-foam pieces hosting the cells are proposed, the purpose being to select the variant with the highest likelihood of optimum performance, in the absence of a detailed mathematical model. A simple model is proposed, drawn from the discipline of hydraulic dynamical systems, which leads to a flow-complexity measure. The variant with the lowest complexity is then selected, for which a possible embodiment is proposed.

Commentary by Dr. Valentin Fuster
2008;():437-447. doi:10.1115/DETC2008-49347.

Stress and Strength Interference Theory (SSIT) is a fundamental theory for reliability assessment. It has been widely used as a foundation for design-for-reliability (DFR). However, SSIT and associated methodology and tools, that require detailed definitions of constructional and form structure, are only applicable to an embodiment design. As many researchers have attempted to push DFR upfront to a conceptual and functional design stage, SSIT loses its usefulness, while other equivalent theory and tools for conceptual and functional design-for-reliability do not exist. Therefore, DFR for conceptual and function design becomes ad-hoc that lacks a systematic approach and parametric reliability quantification. In this paper, we first review the literature on stress and strength interference, and then extend the concepts of stress and strength to conceptual stress and conceptual strength that are relevant to conceptual and functional designs. Based on the conceptual stress and conceptual strength, we introduce a Conceptual Stress and Conceptual Strength Interference Theory (CSCSIT) and discuss how it can be applied to support conceptual and function design-for-reliability. We illustrate our theoretical work with a conceptual and function design example. We conclude the paper with a discussion of the future research to further define and substantiate the CSCSIT work.

Topics: Reliability , Stress , Design
Commentary by Dr. Valentin Fuster
2008;():449-456. doi:10.1115/DETC2008-49350.

Extreme cases that contain either extremely high or pretty low preference attribute(s) are investigated for multi-attribute decision making problems. Normal cases occur most of the time, and many existing methods have been developed to support the decision making in such scenarios. Extreme cases are possible in real applications, and they are usually present intriguing scenarios because of the potential fuzzy and varying decision criteria. To capture this phenomenon, varying weights are introduced to simulate the change pattern concerning relative importance of attributes, and a uniform framework has been developed to support the decision making mathematically for extreme cases. A real application from Industrial Assessment Center at Oregon State University is used to demonstrate the proposed method, and the result shows its capability of capturing a decision maker’s flexible decision altitudes, and indicates its advantage over existing constant weight methods.

Topics: Decision making
Commentary by Dr. Valentin Fuster
2008;():457-467. doi:10.1115/DETC2008-49359.

In this paper, we introduce a new risk-informed decision-making methodology for use during early design of complex systems. The proposed approach is based on the notion that a failure happens when a functional element in the system does not perform its intended task. Accordingly, risk is defined depending on the role of functionality in accomplishing designed tasks. A simulation-based failure analysis tool is used to analyze functional failures and their impact on overall system functionality. The analysis results are then integrated into a decision-making framework that relates the impact of functional failures and their propagation to decision making in order to guide system level design decisions. With the help of the proposed methodology, a multitude of failure scenarios can be quickly analyzed to determine the effects of decisions on overall system risk. Using this decision-making approach, design teams can systematically explore risks and vulnerabilities during early, functional stage of system development prior to the selection of specific components. Application of the presented method to a reservoir system design demonstrates these capabilities.

Commentary by Dr. Valentin Fuster
2008;():469-479. doi:10.1115/DETC2008-49360.

Ocean wave power is still in its infancy. New systems are conceptualized on nearly a daily basis. The systems vary wildly in complexity and scope, but share one common trait; they have never been built. This scenario is ripe with massive financial risk and of course the possibility of reward. Providing an early stage failure and safety analysis could greatly improve the design process by identifying potential weak points in the system prior to the costly build and testing stages of product development. More broadly, determining potentially successful conceptual designs which should be pursued becomes critical. However, there is currently no tool readily available for such a task. In this paper, we adapt and simplify function-based modeling and analysis to fill this void. Completing a function based failure analysis allows engineers to evaluate the dependencies and fault tolerance of their system early in the design stage. This process aids in catching design problems when they are still relatively cheap to address. This paper proposes the System Functionality Method for conceptual design stage analysis. This proposed method places systems and subsystems in a flow (mass, energy, and signal) based on their location, and assigns functionality numbers to help describe their contribution to the system. Component or sub-system faults are then used to determine the effect on other components and the system as a whole. The process is unique in its simplicity and adaptability to the conceptual stage of designing wave energy technologies.

Commentary by Dr. Valentin Fuster
2008;():481-493. doi:10.1115/DETC2008-49361.

The 21st century brings many new challenges to the product development (PD) community mainly due to a drastic increase in the scale and complexity of engineered systems. This requires the collaboration of various entities and resources within and outside firm boundaries. To address these new challenges, this paper proposes a novel framework for an enterprise-wide PD information management system. The proposed framework provides an integrative view of the various dependencies and information flows that co-exist in three main PD analysis domains (i.e., people, products, and processes) and analysis methods for the discovery of gaps or ‘misalignment’ between them. These gaps could help explain why some organizations are able to provide more competitive products within a given industry. Moreover, the framework suggests that the characteristics of how an organization acquire data, interpret information, and apply knowledge will impact the final architecture of the product. Finally, we demonstrate this framework by analyzing an open source software (OSS) project, which offers some insights and new directions into how the transfer of data, information, and knowledge impacts the final (source code) architecture and design.

Commentary by Dr. Valentin Fuster
2008;():495-503. doi:10.1115/DETC2008-49980.

Case studies are used in design research to analyze a phenomenon, to generate hypotheses, and to validate a method. Though they are used extensively, there appears to be no accepted systematic case study method used by design researchers. Considering its nature and objectives, the case study method could be considered as a suitable method for conducting design research. Many times, design researchers have to confront questions about the validity of using case studies and their results. The objective of this paper is to present a brief overview of case study method, compare it with other qualitative and quantitative research methods, and study the merits and limitations of using the same in design research. Requirements are derived from the general characteristics of design research. Four popular research strategies are evaluated with respect to the requirements. A preliminary benchmark study suggests that case study method is a suitable method for conducting design research.

Topics: Design
Commentary by Dr. Valentin Fuster
2008;():505-514. doi:10.1115/DETC2008-50107.

A web forum-based tool for managing user-generated content in engineering design and product development is described. The system is intended to allow a “crowdsourcing” approach, in which large groups perform the work more commonly by individuals. User tests are conducted with an initial implementation, with the system configured in control and “parliamentary” modes. This experiment is done in the setting of a mechanical engineering senior capstone design course. The parliamentary mode is intended to encourage discussion and negotiation among participants, and allows them to design their own work processes. Review of the designs produced together with responses to a survey indicate the system was favorably received, and allowed a group to generate and select concept designs. Future research directions are suggested.

Commentary by Dr. Valentin Fuster

2nd International Conference on Micro- and Nanosystems (MNS)

2008;():517-521. doi:10.1115/DETC2008-49238.

The heat transport in the Al nanopowder is experimentally investigated in this paper. The understanding for thermal behavior of the Al powder is advantageous to the advancement of the processing technologies such as laser cladding, laser sintering, powder metallurgy and its other applications. The powder is wrapped up in the slender tube made of insulating material. One end of the slender tube filled with powder is maintained at temperature 0°C and the other end is kept at 24°C. The temperature histories at two different locations in the slender tube are recorded using thermal couples. The results show that the temperature in the powder composed of nanoparticles descends more quickly than that in bulk material. The increase of pressure on the powders enhances the heat transfer.

Topics: Heat
Commentary by Dr. Valentin Fuster
2008;():523-527. doi:10.1115/DETC2008-49461.

The use of carbon nanotube forest as a brush tool to refine the surface roughness of brass in nanometer scale was reported. The carbon nanotube with a height of 700∼800 μm was first synthesized on silicon wafer by chemical vapor deposition. The carbon nanotube forest on silicon wafer was then transferred and bonded onto a stainless steel wheel. The wheel with carbon nanotube forest was installed on a precision milling machine and used to brush the surface of a brass specimen. The influence of various feed amount, brushing speed and brushing time on the surface roughness of the brass specimen were experimental evaluated. The results show that the increasing feed amount effectively reduces surface roughness of the brass specimen from 20 nanometers to 1 nanometer. Scanning electron microscopy images reveal the evidence of the bushing process that brass chips were melted on the tip of carbon nanotube forest.

Commentary by Dr. Valentin Fuster
2008;():529-533. doi:10.1115/DETC2008-49507.

An improved theoretical approach is presented to calculate and predict the quality factors of flexible microcantilevers affected by squeeze-film damping at low ambient pressures, and moderate to high Knudsen numbers. Veijola’s model [1], originally derived for a rigid oscillating plate near a wall, is extended to a flexible cantilever beam and both the gas inertia effect and slip boundary condition are considered in deriving resulting damping pressure. The model is used to predict the natural frequencies and quality factors of silicon microcantilevers with small gaps and their dependence on ambient pressure. In contrast to non-slip, continuum models, we find that quality factor depends strongly on ambient pressure, and that the damping of higher modes is more sensitive to ambient pressure than the fundamental.

Commentary by Dr. Valentin Fuster
2008;():535-538. doi:10.1115/DETC2008-49818.

The dominance of adhesive forces at the nanoscale implies that significant friction forces can be generated at the interface even with no externally applied normal load. We have nanofabricated an adhesion-friction force sensor to characterize friction in zinc oxide nanowires on silicon substrates. Experimental results show static friction coefficients for zero externally applied normal load can be as high as 45. This behavior is observed to be strongly influenced by the ambient conditions and we propose that the presence of molecularly thin moisture layers is responsible for the observed pseudo-static friction. The findings of this study will provide valuable input to nanoscale interfacial systems such as nanowires and nanotube based sensors and nanocomposites.

Commentary by Dr. Valentin Fuster
2008;():539-542. doi:10.1115/DETC2008-49821.

Thin film specimens of titanium - titanium nitride multilayer erosion resistant coating were prepared using liftout technique in Focused Ion Beam - Scanning Electron Microscope (SEM). The fracture toughness of the thin film specimen was measured in situ using a cantilever bending experiment in SEM to be 11.33 MPa/m0.5 , twice as much as conventional TiN coatings. Ti–TiN multi-layer coatings are part of a new class of advanced erosion resistant coatings and this paper discusses an experimental technique to measure the fracture toughness of these coatings.

Commentary by Dr. Valentin Fuster
2008;():543-545. doi:10.1115/DETC2008-49842.

The purpose of this paper is to show AFM verification of adhesion reduction between valve seat/membrane interfaces by surface coatings from a C4 F8 /Ar plasma in an ICP DRIE. Our check valves utilize a polyimide (PI, Polyimide 5878G, HD Microsystem) membrane on a Si/SiO2 valve seat. These valves form a seal between a polished Si/SiO2 substrate and a smooth polymer membrane. PI absorbs moisture up to 3.4% wt per volume, and the SiO2 surface also has an affinity to water. The smooth PI membrane touches the SiO2 surface, giving rise to relatively strong van der Waals adhesion. Under humid conditions, hydrogen-bonded stiction can occur at the interface between the PI and SiO2 during the drying step. The C4 F8 /Ar plasma coating is utilized for the actual device in order to lower the interface adhesion between Si/SiO2 and PI film. The opening pressures of devices with/without CFn film are measured. The valves without non-stiction coating did not open with inlet pressures up to 210 KPa. With a non-stiction coating, the valves showed an initial opening pressure of 32.5±11 KPa. AFM pull-off measurements using nano-sized tips and micro sized tips are performed to quantify the effect of the CFn film-treated surface between solid-solid surface pairs. The original surface pair for the microvalve membrane and seat surface is Si/SiO2 and PI film. The CFn film treatment is possible on one or both sides of the surfaces. AFM pull-off testing has been performed to measure the work of adhesion between four possible surface combinations, including SiO2 /PI, CFn /PI, CFn /SiO2 , and CFn /CFn . The work of adhesion of the surface pairs is obtained using the Johnson-Kendall-Roberts (JKR) theory. Two types of AFM probes were used, a regular nano-sized AFM probe and a one micron particle AFM probe. The work of adhesions obtained for the pairs above are 257.6±37.1, 59.4±29.2, 89.6±18.2, and 41.0±8.2 [mJ/m2 ] from regular tips, and 159.48±4.0, 41.9±2.0, 65.7±12.2, and 37.4±3.7 [mJ/m2 ] from the particle tips. The CFn film treatment reduced the adhesion energy up to 84% for the regular AFM tip results, and up to 76.7% from the particle AFM tip results. The static contact angle of CFn film with respect to de-ionized water is 116.4 ± 0.9°. The surface coatings from a C4 F8 /Ar plasma in an ICP DRIE can reduce the contact adhesion forces and capillary forces during the fabrication process preventing stiction.

Commentary by Dr. Valentin Fuster
2008;():547-552. doi:10.1115/DETC2008-49897.

Microactuators provide controlled motion and force for applications ranging from RF switches to rate gyros. Large amplitude response in piezoelectric actuators requires amplification of their small strain. This paper studies a uniflex microactuator that combines the strain amplification mechanisms of a unimorph and flexural motion to produce large displacement and blocking force. An analytical model is developed with three connected beams and a reflective symmetric boundary condition that predicts actuator displacement and blocking force as a function of the applied voltage. The model shows that the uniflex design requires appropriate parameter ranges, especially the clearance between the unimorph and aluminum cap, to ensure that both the unimorph and flexural amplification effects are realized. With a weakened joint at the unimorph/cap interface, the model accurately predicts the displacement and blocking force of four actuators.

Commentary by Dr. Valentin Fuster
2008;():553-559. doi:10.1115/DETC2008-49911.

The Young’s modulus of zinc oxide nanowires was measured to be significantly lower than bulk zinc oxide, which cannot be explained within the framework of existing theories. We propose that the strong electromechanical coupling in piezoelectric materials, such as zinc oxide, influences the measured mechanical properties. The asymmetric wurtzite crystal structure and the ionic nature of the molecular bonding result in internal electric fields during straining of the zinc oxide nanowire, which in turn lead to reduction in the measured modulus. In case of flexural deformation, additional electromechanical coupling is present due to the flexoelectric effect.

Topics: Elasticity , Nanowires
Commentary by Dr. Valentin Fuster
2008;():561-568. doi:10.1115/DETC2008-49949.

The impact dynamics of micro-scale mechanisms deviates from the classical theories applied to traditional macro-systems, This is because of multiplicity of forces acting in nano-scale contacts, which have negligible effect at the larger scale. A fundamental understanding of these forces and their interplay is required to advise design of such mechanisms based on fundamental physics. The paper highlights the significance of some of these forces and circumstances where their influence becomes significant.

Commentary by Dr. Valentin Fuster
2008;():569-572. doi:10.1115/DETC2008-50077.

Microlens and its mold fabricated by thermal reflow using photoresist have been widely used for forming patterns in different scales. When the photoresist solidifies from melting condition, for example by the reflow process, its profile is formed based on the balance between surface tension and gravity. This research is aimed to investigate the influence of surface tension and gravity on the profile of microlens in thermal reflow process. Theoretical analysis based on the interaction between surface tension and gravity of liquid droplet is first investigated. The result showed that the height to diameter ratio (h/D), or the sag ratio, of the liquid droplet is affected by the Bond number (Bo), a number defined as the ratio of gravity to surface tension. The sag ratio is not sensitive to Bo when Bo is small but the ratio decreases as Bo increases if Bo is over the critical number. Based on the analysis, the critical number for the AZ4620 photoresist on a silicon substrate is 1, corresponding to the critical radius of droplet R = 2,500μm. When the size of the droplet is less then the critical size, the profile is mainly controlled by the surface tension and thus the sag ratio is about the same regardless the size. The profile, in contrast, is highly affected by the gravity if the size of the droplet is larger then the critical size. The sag ratio decreases exponentially with respect to Bo in this case. Experiments are also designed and conducted to verify the analysis. Experimental result showed that the sag ratio of the photoresist reduces to 0.065 from 0.095 when Bo increases from 0.0048 to 0.192. The results showed that the trend is consistent to the theoretical model.

Commentary by Dr. Valentin Fuster
2008;():573-580. doi:10.1115/DETC2008-50143.

This paper presents a theoretical and experimental investigation on the effects of squeeze film damping and electrostatic forces on the shock spectrum of a capacitive accelerometer. For the theoretical part, a single-degree-of-freedom system is used to model the device. Simulation results are demonstrated in a series of shock spectra that help indicate the nonlinear effects on the motion of a MEMS device. When squeeze-film effects are absent, the electrostatic forces soften the microstructure and increase its deflection significantly. A range of shock durations was found in which the microstructure experiences pull-in (pull-in zone). Larger pull-in zones are obtained as we raise the electrostatic force. On the other hand, the presence of squeeze film highly suppresses the deflection of the microstructure in the dynamic range and has minor effects in the quasi-static range. It is found in the other case that the microstructure experiences pull-in in the quasi-static range. Simulation results are compared to experimental data, showing excellent agreement.

Commentary by Dr. Valentin Fuster
2008;():581-587. doi:10.1115/DETC2008-49178.

This paper presents a novel micro-scale passive-latching mechanical shock sensor with reset capability. The device integrates a compliant bistable mechanism, designed to have a high contact force and low actuation force, with metal-to-metal electrical contacts that provide a means for interrogating the switch state. No electrical power is required during storage or sensing. Electrical power is only required to initialize, reset, self-test, or interrogate the device, allowing the mechanism to be used in low-power and long shelf-life applications. The sensor has a footprint of about 1 mm2 , allowing multiple devices to be integrated on a single chip for arrays of acceleration thresholds, redundancy, and/or multiple sense directions. Modeling and experimental results for a few devices with different thresholds in the 100g to 400g range are given. Centrifuge test results show that the accelerations required to toggle the switches are higher than current model predictions. Resonant frequency measurements suggest that the springs may be stiffer than predicted. Hammer-strike tests demonstrate the feasibility of using the devices as sensors for actual mechanical shock events.

Commentary by Dr. Valentin Fuster
2008;():589-592. doi:10.1115/DETC2008-49545.

This paper describes the development of new micro gas chromatographic column designs intended to optimize the analysis by improving homogeneity of analyte molecules as they progress along the column length. We are particularly interested in applying these approaches for trace analysis of illicit materials such as explosives and other hazardous chemicals. A significant component of this work has been in using computational fluid dynamic (CFD) modeling as a tool to help in optimization of the GC column design.

Topics: Simulation , Design
Commentary by Dr. Valentin Fuster
2008;():593-597. doi:10.1115/DETC2008-49594.

Mechanical and electromechanical parametric amplifiers have garnered significant interest, as of late, due to the increased need for low-noise signal amplification in resonant micro/nanosystems. While these devices, which are traditionally designed to operate in a linear range, potentially represent an elegant, on-chip amplification solution, it is not readily apparent that this technical approach will suffice in all micro/nanoresonator implementations, due to the scale-dependent nature of a mechanical or electromechanical amplifier’s dynamic range. The present work investigates whether the aforementioned linear dynamic range constraint is truly a practical limitation, by considering the behavior of a representative degenerate parametric amplifier driven within a nonlinear frequency response regime. The work adopts a comparatively simple lumped-mass model for analysis and proceeds with the characterization of pertinent performance metrics, including gain/pump and gain/phase behaviors. Ultimately, the work concludes that parametric amplification can be realized in a nonlinear context, but such implementations generally lead to inferior amplifier performance.

Commentary by Dr. Valentin Fuster
2008;():599-604. doi:10.1115/DETC2008-49843.

MEMS mass sensors are an important field of study for chemical and biological sensing. We utilize the massive surface area to volume ratio of tin oxide nanowires to improve the sensing characteristics of resonant cantilever gas sensors. The nanowires are grown onto released silicon cantilevers via the vapor liquid solid method, a type of chemical vapor deposition. Through intelligent catalyst placement the nanowires are grown selectively onto predefined surfaces of the cantilever. The increased surface area of our nanowire coatings provides greatly increased active binding area for analytes, while high quality factors are still achieved with this method. Our experiments actively monitor the removal of a silane self assembled monolayer from the sensor surface. Current nanowire coated sensors show a tenfold increase in sensitivity when compared to the bare sensors. We have functionalized the nanowires with a variety of polymer coatings. These functionalized sensors also show a substantial increase in sensitivity to the analytes. By varying the polymer coating applied to the nanowires, a sensor array can be generated that achieves gas recognition while having incorporated the increased sensitivity of the nanowire coatings.

Commentary by Dr. Valentin Fuster
2008;():605-611. doi:10.1115/DETC2008-50122.

In this work, we demonstrate the concept of a new type of mass sensor detector. The detector is designed to act as a switch that is triggered if the measured mass exceeds a threshold value. The basic idea of the proposed switch is based on utilizing the escape phenomenon that the nonlinear electrostatic force introduces to the dynamics of a capacitive microcantilever. The detector is excited electrostatically with a frequency near the primary or the sub-harmonics (twice the natural frequency) resonances a way from the instability frequency band (escape phenomenon). By absorbing a threshold mass of a target material, the natural frequency of the cantilever will change in a way that it starts to oscillate in the unstable zone and hence hits the substrate. This action could be utilized to activate, for example, an alarming system indicating that the measured material has exceeded the allowable threshold mass (concentration) value.

Topics: Sensors
Commentary by Dr. Valentin Fuster
2008;():613-617. doi:10.1115/DETC2008-49283.

Lead Zirconate Titanate Oxide (PbZrx Ti1−x O3 or PZT) is a piezoelectric material widely used as sensors and actuators. For microactuators, PZT often appears in the form of thin films to maintain proper aspect ratios. A common design is PZT membrane microactuator, whose actuation portion takes a form of a thin diaphragm driven by a PZT thin film. To maximize actuation displacements, finite element analyses are conducted to identify critical design parameters of the PZT film. In the simulation, a constant driving electric field is maintained and boundary conditions of the PZT film are varied. The finite element analyses lead to two important results. First, the actuator displacement increases as the PZT film thickness increases, but saturates at a critical PZT film thickness. Second, when stress relief grooves are introduced and the PZT film surrounding the membrane area is removed, the actuator displacement increases substantially by at least a factor of 5.

Commentary by Dr. Valentin Fuster
2008;():619-628. doi:10.1115/DETC2008-49525.

An improved understanding of the three-dimensional behavior of fully compliant bistable micromechanisms (FCBMs) would facilitate their appropriate implementation in applications such as threshold sensing arrays. A 3-D finite element model was developed to analyze the motion of a nominal FCBM design with various eccentric and off-axis loading conditions. Roll, pitch, and yaw rotations and Z-direction deflection results are presented for various loading conditions. Two distinct behaviors are discussed. Phenomenon 1 occurred when no off-axis loads were applied or when the magnitudes were small. Phenomenon 1 is characterized by shuttle motion with a relatively large pitch rotation. Phenomenon 2 occurred for larger magnitudes of off-axis loads, and was characterized by larger Z-direction deflections, lower actuation forces, and occasional loss of bistability.

Commentary by Dr. Valentin Fuster
2008;():629-631. doi:10.1115/DETC2008-49543.

In this paper, we present the preliminary results of the modification of topology optimized polysilicon microgrippers by focused ion beam (FIB) milling. The main aim of the experiments we performed is to functionalize a faulty microgripper by separating the merged end-effectors with a sub-micron gap and reshaping them to achieve a smaller contact area with the manipulated object. However, the method proposed is also rather important for recovery of the dimensional accuracy or missing features during fabrication. Furthermore, it will enable realization of the inverse microgripper concept, which is not possible with conventional UV lithography.

Commentary by Dr. Valentin Fuster
2008;():633-640. doi:10.1115/DETC2008-49546.

Microelectromecahanical system (MEMS) actuation is a growing area of research. One obstacle for use of actuation in MEMS applications is the difficulty of proper sensing. Recent work has been done that shows the potential for thermomechanical in-plane microactuators (TIMs) to act as self-sensors by using the piezoresistive characteristic of silicon. However, in order to implement this technology a calibration method needs to be devised to account for variations between TIMs. This work presents an approach for this calibration consisting of two parts that compensate for variation in fabrication and material properties. Test structures are presented that will enable this calibration to be done on-chip, and validation is given for the usability of this approach. Two validation approaches are used. For the first approach, data previously gathered was analyzed using the TIM itself for calibration. This approach showed significant correlation with the model; however, this approach confounds any sensing signal and therefore was used only for general model validation. The second approach uses a novel calibration structure that decouples the mechanical and electrical characteristics. This approach showed correlation with test data within the bounds of experimental uncertainty in nearly all cases. Suggestions are given concerning implementation.

Commentary by Dr. Valentin Fuster
2008;():641-646. doi:10.1115/DETC2008-49731.

This article presents a side electromechanical instability of slender comb-fingers in MEMS electrostatic devices. Two models are developed for predicting such side pull-in of comb-fingers; one is based in the lumped modeling technique and another is developed by FEM approach. In the slender finger array, the deflection of every finger and pull-in voltage can be calculated by the models. Results indicate every comb-finger bends with different amplitudes. In the finger array, few sided fingers are strongly deflected, the extreme sided fingers in particular, while other inner fingers show negligible deformations. We suggest these extreme sided fingers can dominate the side pull-in of the comb-fingers and should be considered with careful device design by employing the proposed models in this paper.

Commentary by Dr. Valentin Fuster
2008;():647-654. doi:10.1115/DETC2008-49792.

The vibrations of microcantilevers in Atomic Force Microscopes (AFM) or Radio Frequency (RF) switches strongly couple to the viscous hydrodynamics of the surrounding fluid in the vicinity of a solid wall. While prior efforts have focused on squeeze film damping effects at high Knudsen and squeeze numbers, the regime of low Knudsen and squeeze numbers is also very important for which squeeze film models need to be discarded in favor of unsteady Stokes hydrodynamics. We present convenient semi-analytical expressions for the unsteady viscous hydrodynamic functions of slender microbeams oscillating near solid walls in terms of key non-dimensional numbers. Using these expressions it becomes possible to predict semi-analytically the quality factors of multiple modes of microcantilever beams near solid walls in diverse applications ranging from AFM in liquids to RF microswitches under ambient conditions. The predictions compare favorably with fully three dimensional, transient flow-structure interaction computations as well as with preliminary experiments on cantilevers under ambient conditions.

Commentary by Dr. Valentin Fuster
2008;():655-661. doi:10.1115/DETC2008-50002.

This paper presents the integrated design of an electrostatic comb-drive rotary actuator and a compliant slider-crank mechanism to transmit the motion from a rotary actuator into translational motion. This integrated design yields a transmission exhibiting minimal sliding contact with supporting substrate. This design is applicable to micro-Parallel Kinematic Mechanisms (PKM) for micro/nano positioning and manipulation of optical components including lenses and mirrors. For a 3 degree of freedom micro-PKM, the rotational motion of three electrostatic torsion actuators is converted into translational motion through a compliant transmission device. The compliant transmission is based on a slider-crank mechanism that uses flexible beams for the linkages. The input of the rotary motion through the transmission’s crank yields translational motion of the slider component. The slider is supported via a Roberts straight-line mechanism which yields a suspended slider design and therefore reduced friction and wear within the transmission. Furthermore, the slider component of the transmission provides a linear force-displacement relationship beneficial for embedded sensing. This paper describes the design of the actuation and transmission system and its integration into the kinematics of the micro PKM motion.

Topics: Mechanisms
Commentary by Dr. Valentin Fuster
2008;():663-667. doi:10.1115/DETC2008-50019.

In atomic force microscopy (AFM) -based single molecule force spectroscopy, it is assumed that the pulling angle is negligible and that the force applied to the molecule is equivalent to the force measured by the instrument. Although this assumption may hold for flexible, compact molecules, studies have shown that it may not be appropriate for fairly rigid molecules, where measured forces can be a fraction of the actual values experienced by the molecule. Previously, we have proposed a method to align a molecule’s substrate and cantilever attachment sites and tested it in a simulated environment. Here we continue our work and test the alignment program in an experimental environment. In this paper we demonstrate that circling-induced force fluctuations are the result of stretching and relaxing a tethered molecule and we present the results of an alignment trial. Combined, these preliminary results demonstrate the feasibility of the alignment program and are a promising step towards correcting pulling geometry errors in single molecule force spectroscopy studies.

Commentary by Dr. Valentin Fuster
2008;():669-675. doi:10.1115/DETC2008-50076.

A new bio-mimetic MEMS actuator device with self-sensing used for thrombus retrieving is presented. The device contains four laterally apposed triangular teeth forming a square which is inspired by the jaws of an earthworm that has radial teeth around a circular mouth. Each tooth is fixed only at the perimeter of the square and consists of several layers including piezoelectric material (PZT) layers, electrode layers (Ti/Pt) and diffusion barrier layers. Due to mismatch of thermal expansion coefficients of different layers, each of the four triangular teeth would initially curve up after the micro fabrication opening the “jaws” of the device. The teeth can then be driven to a closed position by applying an electric field to the PZT layers. The self-sensing method of the piezoelectric device is used for detecting the external force exerted by the teeth and feedback control system in this bio-mimetic MEMS actuator device. The mathematic model which can be used to calculate and control the residual stress causing the curvature of these teeth is discussed. Additionally, residual stress coupled with the piezoelectric stress and external force is also considered. The materials and thickness are optimized by using the linear model developed in this paper. Moreover, with this mathematic model and geometry of these teeth, the motion tracks driven by two different modes are simulated.

Commentary by Dr. Valentin Fuster
2008;():677-682. doi:10.1115/DETC2008-50134.

In this paper, we present a mathematical model and analysis for a microbeam fixed at one end and coupled to a microplate at its other end under the effect of capillary, shock and electrostatic forces. The model considers the microbeam as a flexible structure, the plate as a rigid body. First, we subject the system to capillary force via a drop of fluid which is trapped underneath the microplate. We derive closed-form solutions to the static and eigenvalue problems associated with the microbeam-microplate system. We then subject the system to shock loads for both case (capillary and electrostatic forces). The Galerkin procedure is used to derive a set of nonlinear ordinary-differential equations that describe the microsystem dynamics. We investigate the influence of the fluid volume ratio and the applied DC voltage on the microbeam response. We find that the effect of capillary force has much more dominant role compared to shock and electrostatic forces.

Commentary by Dr. Valentin Fuster
2008;():683-687. doi:10.1115/DETC2008-49260.

With advancements in nanotechnology and the continuing reduction of the minimum feature size in integrated-circuit technologies, there is a need for next-generation lithography (NGL) tools. The direct transfer of grating structures stitched from interference lithography to a mold for nano imprinting offers a low-cost alternative for printing sub-100nm features with great potential accuracy, high resolution, and reductivity. This research presents dual stage laser-interferometer equipment to meet these requirements. In moving forward to the stitching of a small interference area, the most important issue is alignment. If the period of this interference fringe can be guaranteed, the stage can be moved in chronological alignment with the period. This paper also presents SEM results of stitching of a 600nm periodic structure.

Commentary by Dr. Valentin Fuster
2008;():689-693. doi:10.1115/DETC2008-49647.

In this paper, we present a new thermal reflow method to transform photresist pillars into the shapes of spherical caps and month-eyes. We also investigated the effect of this sub-wavelength structure morphology on anti-reflection properties of these photoresist patterns. The diameter, the height, and the pitch of this regularly arranged pillar array were set at 200, 250, and 340 nm, respectively. After the thermal reflow, experimental results showed that the reflectivity of the heat-treated photoresist patterns can be reduced to approximately one fourth of that of the polished surface of the silicon wafer.

Commentary by Dr. Valentin Fuster
2008;():695-700. doi:10.1115/DETC2008-49766.

It is well known that metallic nanostructures can be potentially applied in many fields. Direct nanoimprint features an uncomplicated and efficient fabrication process of the metallic nanostructures. This paper contributes to the investigation of the formation and friction in direct nanoimprint process by utilizing molecular dynamics (MD) simulations. The MD model consists of a silicon mold and an aluminum thin film. For the formability, the phenomenon of springback and mold cavity filling ratio are investigated first under conditions of various imprinting depths and film thicknesses. For the friction, the friction mechanisms induced on the mold are studied subsequently. Since a nickel mold is adopted in many industrial applications, it is also simulated to compare with the silicon mold for the purpose of illustrating the material effect on friction mechanisms. This study explores not only friction mechanisms at different stages of the process but the friction force affected by various geometric configurations of the mold, for example, linewidth-to-pitch ratio and surface roughness. This work also provides the general concept that which force dominates the process force and what percentage of the friction force takes in the imprinting force.

Commentary by Dr. Valentin Fuster
2008;():701-711. doi:10.1115/DETC2008-50114.

Flexure-based compliant mechanisms are the preferred motion guiding systems for small range, nano-precision positioning applications because of excellent characteristics like friction-free continuous motion. These mechanisms are commonly used in nano fabrication equipment and ultra precision instruments. However, machining imperfections induced geometric errors in the mechanisms are known to cause undesirable parasitic motion and significant loss of precision. A systematic design approach to minimize the sensitivity of the flexure mechanisms to geometric errors induced by machining tolerances is presented here. Central to the design approach is the screw systems based analytical model to study the spatial motion characteristics of flexure mechanisms. Using this model, the parasitic motion is classified into those errors which can be corrected by calibration (extrinsic) and those which are coupled with the mechanism motion and cannot be corrected by apriori calibration (intrinsic). Metric to quantify the intrinsic parasitic motion results naturally from the screw systems analysis, and is used to represent the precision capability of the flexure mechanism. The analytical model enables the selection of geometric parameters of flexure joints of the mechanism via an optimization scheme with the aim of minimizing the parasitic motion metric. The statistical nature of the machining tolerances is accounted for by sampling the random variables at every iteration step of the optimization, leading to a stochastic formulation. The robust design approach is illustrated using a one DOF rotational flexure mechanism that is used in nano-imprint lithography equipment. Numerical results of the optimization indicate up to 40% improvement in the precision capability of the mechanism without any change in the manufacturing tolerance limits. Further, it is shown via eigenscrew analysis of mechanism compliance that the robustness resulting from the optimal flexure joint design can be attributed to the improved compliance distribution.

Commentary by Dr. Valentin Fuster
2008;():713-718. doi:10.1115/DETC2008-49182.

This study performs a series of experimental investigations to determine the temperature and pressure conditions which maximize the quantities of caffeine and EGCG extracted from green tea using a supercritical fluid extraction process with a carbon dioxide solvent. The experimental data are then used to construct a fuzzy model for predicting the extractant quantities given the temperature and pressure conditions of the extraction process. The average discrepancy between the experimental results and the predicted results for the quantities of caffeine and EGCG extracted at temperatures of 40°C, 50°C and 60°C, respectively, is found to be just 7.38%, thus confirming the viability of the fuzzy model as a predictive tool. Overall, the results reveal that a temperature of 40°C and a pressure of 2500 psi represent the optimum extraction conditions for both caffeine and EGCG.

Commentary by Dr. Valentin Fuster
2008;():719-722. doi:10.1115/DETC2008-49503.

Biocompatible magnetic nano-particles show great potential in bio-magnetic applications. In this work, the feasibility of magnetically labeled immunoassay using bio-compatible magnetic nanoparticles is investigated. To do this, we study the synthesis technologies for magnetic nano-particles Fe3O4, as well as the coating of various bio-probes onto the magnetic nanoparticles to detect bio-targets, such as proteins, virus, etc. Furthermore, the measurement, magnetoreduction assay, for the amount of bio-targets are developed. The results show such merits as high-sensitivity, high-specificity, high-convenience for magnetoreduction assays using magnetic nanoparticles. The whole assay platform is promisingly applied to food inspection, environment monitoring, and even human diagnosis.

Commentary by Dr. Valentin Fuster
2008;():723-730. doi:10.1115/DETC2008-49548.

The ultimate goal of this work is to develop an automated MEMS-based lab-on-a-chip microinjector. This paper outlines one phase of that work: testing the feasibility of a pumpless, polysilicon MEMS microneedle for use in the proposed MEMS-based lab-on-a-chip microinjector. The pumpless MEMS microneedle operates on the principle of attraction and repulsion of DNA using electrostatic charges. Prototype microneedles were fabricated using a multi-layer surface micromachining process. DNA stained with a fluorescent dye (4‘, 6-DIAMIDINO-2-PHENYLINDOLE DIHYDROCHLORIDE or DAPI) was visualized using fluorescent illumination as the DNA was attracted to and repelled from the tips of MEMS microneedles using a 1.5 V DC source. The pumpless MEMS microneedle represents an important and significant step in the development of a self-contained, automated, MEMS-based microinjection system.

Commentary by Dr. Valentin Fuster
2008;():731-736. doi:10.1115/DETC2008-49699.

We present a simple and cost effective approach using electrochemical impedance spectroscopy (EIS) for accurate pore size estimation of silicon based nano-pores. This method accounts for the capacitor effects of the electrical double layer and the resistor effects of the ion concentration inside the nano-channel. The nano-pore impedance was modeled as the electrolyte charge transfer resistance Rs in a series connection with a parallel ion diffusion circuit Rf with a constant phase element (CPE) that models the behaviour of the double layer. The EIS analysis that has been widely employed to measure the energy storage and dissipation properties of a physicochemical system in frequency domain was adopted to sense the impedance parameters of the nano-pore. The nano-pore size was then estimated based on the impedance parameters. The accuracy of the estimated nano-pore size was verified by the TEM image.

Commentary by Dr. Valentin Fuster
2008;():737-741. doi:10.1115/DETC2008-49555.

A coupled pair of 500 μm length microcantilevers was excited using the ultrasound radiation force. The excitation was produced using the difference frequency between the two sidebands of a double-sideband suppressed carrier AM (DSB-SC-AM) waveform centered on 500 kHz that was emitted by a focused ultrasound transducer. A laser Doppler vibrometer measured the frequency response and deflection shapes of the cantilever pair. The measured frequencies of the symmetric and antisymmetric eigenstates of the first transverse mode at 10 kHz excited using the ultrasound radiation force were consistent with frequencies measured using a scanning-probe microscopy system. The ultrasound radiation force was also used to excite the symmetric and antisymmetric eigenstates of the 60 kHz second transverse and 86 kHz first torsional modes. These results demonstrate the capability of using the ultrasound radiation force for excitation of structures in air that are significantly smaller, and with higher resonance frequencies, than in any previous study.

Commentary by Dr. Valentin Fuster
2008;():743-747. doi:10.1115/DETC2008-49846.

This study has successfully demonstrated a novel tensile testing approach to mount a thin film test specimen onto a MEMS instrument using microfabrication processes. The MEMS instrument consists of a thermal actuator, differential capacitance sensor, and supporting spring. The thermal actuator applies a tensile load on the test specimen to characterize the Young’s modulus and the residual stress of the thin film. As compare with the existing approaches, the problems and difficulties resulting from the alignment and assembly of a thin film test specimen with the testing instrument can be prevented. Furthermore, the parylene passivation technique with the MEMS fabrication process allows the user to change the test materials easily. In application, the present approach has been employed to determine the Young’s modulus and the residual stress of Au and Al films.

Commentary by Dr. Valentin Fuster
2008;():749-757. doi:10.1115/DETC2008-49877.

Atomic force microscope (AFM) based anodization nanolithography generates nanoscale oxide patterns on a silicon substrate in a serial fashion. The design of a custom AFM system allows for the controlled deposition of oxide patterns in the 100 nm regime. Anisotropic etching of the substrates results in raised micro- and nanostructures. The resulting master patterns are shown to be useful for the molding of stamps for soft lithographic patterning at the nanoscale. The simplicity of this method enables prototypical investigation of new materials and processes for soft lithographic research.

Commentary by Dr. Valentin Fuster
2008;():759-764. doi:10.1115/DETC2008-49884.

Optical traps are an important tool in biophysics, which are capable of measuring forces on the the order of piconewtons and displacements on the order of nanometers. When being used as a probe, objects confined in optical traps are subjected to a broad-band thermal noise source known as Brownian motion. Closed loop control offers a method for reducing the magnitude of these disturbances, but controller design is a difficult and time consuming process. Even after a controller has been constructed, changes in the trapping power or changes between particles will change the plant dynamics and ultimately affect how well the controller performs. For these reasons, presented here is a method of designing an adaptive controller which automatically identifies the plant and actuator dynamics and designs a corresponding controller for disturbance rejection. The controller design is easily implemented on any digital control system.

Commentary by Dr. Valentin Fuster
2008;():765-774. doi:10.1115/DETC2008-49931.

A new self-excited micro-oscillator is proposed as a velocity reference that could aid the dissemination of nanonewton-level forces that are traceable to the International System of Units (SI). An analog control system is developed to keep the actuation side of the device oscillating sinusoidally with an amplitude that is fairly insensitive to the quality factor. Consequently, the device can be calibrated as a velocity reference in air and used in ultra-high vacuum with a velocity shift of less than one percent. Hence, the calibrated micro-oscillator could be used with electrostatic forces to calibrate cantilevers used for atomic force microscopy (AFM) as SI-traceable force transducers. Furthermore, the calibrated micro-oscillator could potentially be used as an AFM sensor to achieve atomic resolutions on par with those realized in frequency-modulation AFM (FM-AFM) with quartz tuning forks.

Commentary by Dr. Valentin Fuster
2008;():775-781. doi:10.1115/DETC2008-50020.

The physics of adhesion of one-dimensional nanostructures such as nanotubes, nanocoils, and nanowires is of great interest to the functioning and reliability of nanoelectronic devices and the development of high-strength, lightweight nanocomposites. Here, we extend previous work using the Atomic Force Microscope (AFM) to investigate quantitatively the physics of nanomechanical peeling of carbon nanotubes (CNTs) and nanocoils on different substrates. We summarize previous modeling results which predict that an initially straight nanotube peeled from a surface may transition suddenly between different geometric configurations with vastly different interfacial energies. In contrast, nanocoils display a sawtooth peeling force curve indicating the sequential release of discrete pinning points. We resolve differences in nanotube peeling energies at attoJoule levels on different materials, thus opening up the possibility of sensitive screening of fiber coatings or material surfaces for improved adhesion in nanocomposites.

Commentary by Dr. Valentin Fuster
2008;():783-787. doi:10.1115/DETC2008-50067.

In this paper we present a lithographic process with the ability to automatically translate and arbitrarily position three-dimensional (3D) computer-generated patterns through the use of phase holograms. This method, dynamic maskless holographic lithography (DMHL), advances current photo-directed patterning and functionalization capabilities by expanding the capability to manipulate light in real-time without the use of expensive fixed masks. The system could be used for large-scale parallel manufacturing over larger areas and for point specific serial fabrication, interrogation, and metrology. The use of coherent illumination allows for the direct creation of 3D patterns of light for lithography as opposed to the mechanical stage, layer-by-layer 3D fabrication approach typical of direct-write systems. Extrinsic control over interfacial properties will provide a method for addressing aqueous phase bionanotechnolgy experimental systems in which detection, separation, transport, and handling are vital.

Commentary by Dr. Valentin Fuster
2008;():789-797. doi:10.1115/DETC2008-49232.

Heterogeneous assembly at the microscale has recently emerged as a viable pathway to constructing 3-dimensional microrobots and other miniaturized devices. In contrast to self-assembly, this method is directed and deterministic, and is based on serial or parallel microassembly. Whereas at the meso and macro scales, automation is often undertaken after, and often benchmarked against manual assembly, we demonstrate that deterministic automation at the MEMS scale can be completed with higher yields through the use of engineered compliance and precision robotic cells. Snap fasteners have long been used as a way to exploit the inherent stability of local minima of the deformation energy caused by interference during part mating. In this paper we assume that the building blocks are 2 1/2 -dimensional, as is the case with lithographically microfabricated MEMS parts. The assembly of the snap fasteners is done using μ3 , a multi-robot microassembly station with unique characteristics located at our ARRI’s Texas Microfactory lab. Experiments are performed to demonstrate that fast and reliable assemblies can be expected if the microparts and the robotic cell satisfy a so-called “High Yield Assembly Condition” (H.Y.A.C.). Important design trade-offs for assembly and performance of microsnap fasteners are discussed and experimentally evaluated.

Commentary by Dr. Valentin Fuster
2008;():799-801. doi:10.1115/DETC2008-49540.

In this paper, we present the topology optimization procedure, fabrication and characterization results for electrothermally actuated polysilicon microgrippers for nanomanipulation purposes. In our previous work [1], we compared the performance of topology optimized actuator with the conventional three-beam electrothermal actuators [2] of the same size through finite-element simulations and experiments. Here, we further improve the topology optimized microgripper design and demonstrate the preliminary results of pick-and-place nanomanipulation experiments performed, where carbon nanotubes (CNTs) are transferred on four-point probes for electrical characterization.

Commentary by Dr. Valentin Fuster
2008;():803-810. doi:10.1115/DETC2008-49640.

A 6DOF Stewart platform using piezoelectric actuators for nanoscale positioning objective is designed. A measurement method that can directly measure the pose (position and orientation) of the end-effector is developed so that task-space on-line control is practicable. The design of a sensor holder for sensor employment, a cuboid with referenced measure points, and the computation method for obtaining the end-effector parameters is introduced. A control scheme combining feedforward and feedback is proposed. The inverse model of a hysteresis model derived by using a dynamic Preisach method is used for the feedforward control. Hybrid control to maintain both the positioning and force output for nano-cutting and nano-assembly applications is designed for the feedback controller. The optimal gain of the feedback controller is searched by using relay feedback test method and genetic algorithm. In experiment, conditions with/without external load employed with feedforward, feedback, and feedforward with feedback control schemes respectively are carried out. Performance of each control scheme verifies the capability of achieving nanoscale precision. The combined feedforward and feedback control scheme is superior to the others for gaining better precision.

Commentary by Dr. Valentin Fuster
2008;():811-817. doi:10.1115/DETC2008-50026.

This paper presents a study to improve machining quality concerning the method of drilling ceramics and other hard and brittle materials such as silicon wafers. Instead of making the drill vibrate by the ultrasonic actuator, a new design of PZT-driving ultrasonic workpiece wafer holder is proposed to ensure the high quality, high efficiency and longer life for micro tools in drilling the silicon wafer. In this paper, ultrasonic workpiece holders are first designed by FEA and fabricated experimentally. Then, the ultrasonic holders is used for a series of experiments under different vibration conditions to examine the behavior of drilled hole accuracy, and edge chipping on the drilled hold surface. Also, the behavior of tool during ultrasonic vibration of holder is examined experimentally. The result demonstrates the ultrasonic workpiece holder could enhance the quality and efficiency for drilling silicon wafers.

Commentary by Dr. Valentin Fuster
2008;():819-824. doi:10.1115/DETC2008-49270.

MEMS parallel-plate tunable capacitors have high Q-factors and fast responses to the actuation and therefore are desired for RF applications. However, conventional designs have low tuning ratios and nonlinear capacitance-voltage (C-V) responses which are highly sensitive to the voltage change near pull-in. In this research, a novel structure for parallel-plate-based capacitors is introduced. The capacitor has electrodes with triangular shape and uneven supporting beams and is equipped with a set of middle beams which increases the structural stiffness of the capacitor as bias voltage increases. Because the asymmetric design alters the parallelness of the plates, the stiffness of each middle beam is added to the system at a different voltage causing a smooth increment in structural stiffness. To analyze the capacitor and optimize the design, an analytical model is developed to solve the coupled electrostatic-structural physics. The results of numerical simulations reveal that if the stiffness coefficients of supporting and middle beams are optimized, a highly linear C-V response is obtained. Moreover, since the structural rigidity is gradually increased with voltage, the sensitivity of the response to the voltage change is also improved and a higher tunability over 150% is achieved. The proposed design has a simple geometry and can be fabricated by a three-structural-layer process such as PolyMUMPs.

Commentary by Dr. Valentin Fuster
2008;():825-830. doi:10.1115/DETC2008-49272.

In conventional MEMS parallel-plate capacitor designs, the moving electrode is commonly modeled as a rigid plate with flexible boundary conditions provided by a set of supporting beams. Such a capacitor generates limited tuning ratio up to 1.5 and its capacitance-voltage response is nonlinear. This paper presents novel designs where the moving electrodes are fixed-edge flexible plates. The plate displacement is selectively limited by a set of rigid steps, located between two electrodes, to generate a smooth and linear response and high tunability. Three different step heights are considered in the design and the linearity of the C-V curve is maximized by modifying the geometry of the plate, and changing the location and order of steps. Since the analytical solution for coupled electrostatic-structural physics in this case does not exist, ANSYS® FEM simulation is performed to obtain the C-V curves and optimize the design. Two designs with different electrode shapes, rectangular and circular, are developed. For rectangular-plate capacitors, tunabilities ranging from 120% to 140% and high linearity are achieved. Circular-plate designs, on the other hand, generate lower tunabilities and an extremely linear region in C-V curves. Design methodology introduced in this research is not limited to proposed geometries and can be extended to different topologies to obtain a combination of high tunability and linearity.

Commentary by Dr. Valentin Fuster
2008;():831-837. doi:10.1115/DETC2008-49492.

This paper presents utilization of microgrooved structure in enhancing manipulation of high conductivity fluids with alternating current (AC) electrothermal mechanism with low electric voltage requirement (<10 V ). Two manipulation modes including bidirectional pumping and stationary state can be achieved by changing the electric frequency. Numerical simulations are performed and the effects on electrothermal driven fluid motion in grooved surface structure are investigated. The pumping capacity of several grooved profiles of rectangular, trapezoid and hybrid trapezoid are analyzed and compared. The theoretical analysis as well as the numerical simulation indicates that electrothermal driven micropumping and temperature rise can be controlled in these structures for optimum operations.

Commentary by Dr. Valentin Fuster
2008;():839-847. doi:10.1115/DETC2008-49825.

This paper reports enhanced adhesion and friction of biologically inspired mushroom-shaped elastomer microfibers which are fabricated using micromolding and the notching effect during deep reactive ion etching (DRIE). The fabrication approach of this work allows mushroom-shaped small diameter fibers down to 100s of nanometer scale (using interference lithography) with high uniformity, and high yield in large area. The fabricated microfiber arrays demonstrate approximately up to 17 time higher adhesion and around twice higher static friction than the nonfibrillar flat elastomer surface on a 6 mm diameter glass hemisphere. Moreover, adhesion experiments with the microfiber arrays which have different thickness backing layers reveal the significance of the backing layer thickness on adhesion of the fiber arrays on smooth contact surfaces.

Commentary by Dr. Valentin Fuster
2008;():849-853. doi:10.1115/DETC2008-50115.

We present experimental results on the electrical characterization of single semiconducting carbon nanowires using microfabricated electrodes. The material tested is classified as nanoporous carbon and is a class of amorphous carbonaceous material. Because of amorphous nature of this system the properties of the carbon nanowires are not similar to other crystalline carbon nanowire systems such as carbon nanotubes and graphitic carbon nanowires. Synthesis, experimental characterization techniques and the electron transport mechanism are discussed in this paper. Applications for this carbonaceous material include size-selective catalysis [1, 2], flexible electronic components and as gas sensors [3].

Topics: Carbon , Nanowires
Commentary by Dr. Valentin Fuster
2008;():855-864. doi:10.1115/DETC2008-49184.

Experimental work for characterizing materials’ properties as well as components’ and systems’ behaviors have to be supplemented by numerical analyses when regarding micro components and systems. In order to accomplish a complete possibilities’ overview for micro machines these analyses should cover both component and system issues. On a component level, established macroscopic approaches are extended by methods that allow the consideration of components’ grain structures influence, including possible superficial and internal defects. Because of technological restrictions, especially when applying miniaturized conventional manufacturing techniques, shape and material deviations cannot be scaled down in the same dimensions like micro parts. Thus, high tolerances accepted for the individual components and their effects on the expected transfer behavior of the whole system are taken primarily into account. This paper presents approaches for the simulation of micro components and systems using the Finite Element Method and Multi Body Simulation. Methods to overcome the above mentioned issues will be shown, as well as the effects of grain structure on the stress distribution in the individual components. Some effects over the system’s behavior of this inhomogeneous stress distribution are also discussed.

Topics: Simulation
Commentary by Dr. Valentin Fuster
2008;():865-870. doi:10.1115/DETC2008-49214.

This paper presents a numerical model for thermoelastic damping (TED) in micromechanical resonators made from anisotropic materials, such as single crystal silicon. It is built upon a thermal-energy method, in which TED is interpreted as the generation of thermal energy per cycle of vibration and consequently the mathematical expression for TED is derived from the linear thermoelastic governing equations for anisotropic media. This numerical model consists of two sequential numerical simulations: elastic vibrations and transient heat conduction, and is developed in the ANSYS/Multiphysics, giving rise to the numerical value for the derived expression for TED and further the quality factor related to TED (QTED ) in a micromechanical resonator with any complex structural geometry. Through comparison with experimental data in the literature, the validity of the presented numerical model is demonstrated.

Commentary by Dr. Valentin Fuster
2008;():871-878. doi:10.1115/DETC2008-49470.

A novel 3-DOF parallel micromanipulator which is driven by piezoelectric actuators has been developed that based on 3–5R parallel mechanism. The micromanipulator consists of a moving platform, a fixed platform, three 5R fixed-length chains and three piezoelectric actuators. In this paper, the first-order influence coefficient matrix of the micromanipulator is given, and then the velocity analysis is given. The dimension of the platform and flexure hinges and the position of flexure are designed, and the safety check of the flexible hinges and the designed mechanism is done with the aid of finite element modeling to provide good stiffness with little bending deformation of the platform. The merits of parallel mechanism and piezoelectric actuators are reflected in this mechanism.

Commentary by Dr. Valentin Fuster
2008;():879-886. doi:10.1115/DETC2008-49487.

In this study, a novel design of multiple vibrating membrane micropump has been investigated. The micropump is composed of six membranes and three nozzle/diffuser elements. The membranes were vibrated out-of-phase simultaneously to create pressure difference in the pump chamber. The characteristics of this micropump were analyzed using the finite volume method. The commercial computational fluid dynamics software, FLUENT, with the dynamic mesh algorithm was employed to study velocity field and flow rate during the operating cycle. The simulation results showed that the movement of these membranes combined with the rectification behavior of three nozzle/diffuser elements can minimize back flow and improve net flow in one direction. The average mass flow rate from the micropump increased when the maximum membrane displacement and membrane frequency increased. However, the average mass flow rate from the micropump decreased when pressure head increased. Increases in maximum pressure head were associated with increases in membrane frequency.

Commentary by Dr. Valentin Fuster
2008;():887-894. doi:10.1115/DETC2008-49600.

A continuous protein synthesis formulation based on the design principles developed for structural topology optimization is proposed in this paper. Unlike conventional continuous protein design methods, the Power Law-based (PL) design formulation proposed in this paper enables using any number of residue types to accomplish the goal of protein synthesis and hence provides a continuous protein design formulation applicable to any general protein design problems. Moreover, a discrete sequence with minimum energy can be synthesized by the PL design method as it inherits the feature of material penalization used for the topology optimization. Since a continuous optimization method is implemented to solve the PL design formulation, the entire design process is more efficient and robust than the conventional design methods employing a stochastic or enumerative search process. The performance of the PL design formulation is demonstrated by designing simple lattice protein models for which an exhaustive search can be carried out to identify the sequence with minimum energy. The comparison with the exchange replica method indicates that the PL design method is millions of times more efficient than the conventional stochastic protein design method.

Commentary by Dr. Valentin Fuster
2008;():895-903. doi:10.1115/DETC2008-49617.

The focus of this paper is on designing useful compliant micro-mechanisms of high-aspect-ratio which can be microfabricated by the cost-effective wet etching of (110) orientation silicon (Si) wafers. Wet etching of (110) Si imposes constraints on the geometry of the realized mechanisms because it allows only etch-through in the form of slots parallel to the wafer’s flat with a certain minimum length. In this paper, we incorporate this constraint in the topology optimization and obtain compliant designs that meet the specifications on the desired motion for given input forces. Using this design technique and wet etching, we show that we can realize high-aspect-ratio compliant micro-mechanisms. For a (110) Si wafer of 250 μm thickness, the minimum length of the etch opening to get a slot is found to be 866 μm. The minimum achievable width of the slot is limited by the resolution of the lithography process and this can be a very small value. This is studied by conducting trials with different mask layouts on a (110) Si wafer. These constraints are taken care of by using a suitable design parameterization rather than by imposing the constraints explicitly. Topology optimization, as is well known, gives designs using only the essential design specifications. In this work, we show that our technique also gives manufacturable mechanism designs along with lithography mask layouts. Some designs obtained are transferred to lithography masks and mechanisms are fabricated on (110) Si wafers.

Commentary by Dr. Valentin Fuster
2008;():905-908. doi:10.1115/DETC2008-49819.

Zener’s approximate expression for thermoelastic damping was first known attempt to quantify the thermoelastic damping. Recently, an exact expression of thermoelastic damping for thin unstressed beams, which is widely used, is arrived at. Further, it has been experimentally verified that application of tensile axial stress results in increase in the Q-factor. Since the existing expressions do not take into account the effect of axial stress thermoelastic-damping expression is revised in order to accommodate the effect of axial stress on Q-factor. This expression explains the general behavior observed in experiments. In limiting case of unstressed beam, this new expression converges to current expression for thermoelastic damping.

Commentary by Dr. Valentin Fuster
2008;():909-914. doi:10.1115/DETC2008-49886.

This paper introduces a novel T-beam actuator fabricated by a piezoelectric MEMS fabrication process. ICP-RIE etching from the front and back of a bulk PZT chip is used to produce stair stepped structures through the thickness with complex inplane shapes. Masked electrode deposition creates active and passive regions in the PZT structure. With a T-shaped crosssection, and bottom and top flange and web electrodes, a cantilevered beam can bend in-plane and out-of-plane with bimorph actuation in both directions. One of these T-beam actuators is fabricated and experimentally tested. An experimentally validated model predicts that the cross-section geometry can be optimized to produce higher displacement and blocking force.

Commentary by Dr. Valentin Fuster

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