Micropump With Six Vibrating Membranes: Design Analysis

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.

Meta4acle: Generating Compelling Metaphors for Design

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.

High Yield Assembly of Compliant MEMS Snap Fasteners

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.

An Investigation on the Profile of Microlens by the Thermal Reflow Process Due to Surface Tension and Gravity

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.

Modelling and Simulation of a Cantilever-Paddle Beam Under the Effect of Capillary, Shock, and Electrostatic Forces

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.

Comparison and Application of Metrics That Define the Components Modularity in Complex Products

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.

Piezoelectric T-Beam Microactuators

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.

Testing of a Pumpless MEMS Microinjection Needle Employing Electrostatic Attraction and Repulsion of DNA

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.

Nano-Scale Impact Characteristics of Rough Surfaces in Humid Atmosphere With Full or Partial SAM Protection

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.

DSM-Based Product Representation for Design Process Modularity

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.