John R. Gilbert

3D modeling of contact problems and hysteresis in coupled electro-mechanics

This paper discusses the modeling of electromechanical hysteresis in devices which exhibit contact between components. We make use of a recently developed tool, CoSolve-EM, in order to solve quasistatic 3D contact electro-mechanics for a clamped-clamped beam, calculating full displacement, capacitance and contact force vs. voltage. We then extend the simulations to two design variations of the beam which permit engineering of its hysteresis characteristics.

Implementation of MEMCAD system for electrostatic and mechanical analysis of complex structures from mask descriptions

The development of a first implementation of the MEMCAD system (version 1.0) is reported. The system is composed of three commercial mechanical CAD software packages integrated with specialized structure generation and electrostatic analysis programs. The authors describe the system and demonstrate its capabilities using a comb drive example constructed directly from a CIH description of its mask set. The analysis of the comb drive, all the way from generating a full 3-D model from mask descriptions to calculating comb levitation forces, takes just a few hours.<<ETX>>

Design Analyses of Capillary Burst Valves in Centrifugal Microfluidics

This paper presents current research in analysis of passive microfluidic capillary burst valves. A capillary burst valve stops the liquid flow using a capillary pressure barrier that develops when the channel cross section expands abruptly. Valves of this type provide the capability of precise control on sample location in microfluidic device. Detailed numerical analyses of the valve behaviour is presented and compared with experimental measurements. A model for the valve is then extracted that characterizes the valve performance for various common cross sections.

A relaxation/multipole-accelerated scheme for self-consistent electromechanical analysis of complex 3-D microelectromechanical structures

In this paper, two approaches to self-consistent electromechanical analysis of three-dimensional micro-electro-mechanical structures are described. Both approaches combine finite-element mechanical analysis with multipole-accelerated electrostatic analysis, the first using a relaxation algorithm and the second using a surface/Newton generalized conjugate-residual scheme. Examples are given to demonstrate the relative merits of the two approaches.

Modeling gas damping and spring phenomena in MEMS with frequency dependent macro-models

In this paper, we present an efficient macromodel extraction technique for gas damping and spring effects for arbitrarily shaped MEMS devices. The technique applies an Arnoldi-based model-order-reduction algorithm to generate low-order models from an FEM approximation of the linearized Reynolds equation. We demonstrate that this approach for generating the frequency-dependent gas-damping model is more than 100 times faster than previous approaches, which solve the linearized Reynolds equation using a transient FEM solver. The low-order gas-damping model can be easily inserted into a system-level modeling package for transient and frequency analysis. The simulated results are in good agreement with experimental results for four different devices.

Optimization of sample injection components in electrokinetic microfluidic systems

This paper presents experimental data, simulation tools (FlumeCAD), simulation results, and their use together to analyze and improve the designs of electrokinetic injection and switching components for microchemical fluidic systems.

Design Analysis and 3D Measurement of Diffusive Broadening in a Y-mixer

Diffusive broadening of a low molecular weight species in pressure driven flow is studied using both experiment and numerical analysis. Confocal microscopy allows experimental visualization of the three dimensional nature of the diffusion. Numerical results support the experimental results, and are used to provide insight into design questions about devices involving diffusive mixing.

Extraction of compact models for MEMS/MOEMS package-device codesign

MEMS package requirements are by their nature application specific. MEMS devices are often inherently sensitive to stress induced by their packages sand often need direct access to the environment. Therefore, understanding the influence of packaging on MEMS is critical to a successful coupled package-device co-design. Here, an automated package-device interaction simulator has been developed. The simulator uses Finite Element Method models for both the package and the device analysis and ties the result of the simulations together through parametric models. This so- called Compact Model Extraction is an efficient way to solve complex problems. Several examples illustrate the use of this technique.

Numerical framework for the modeling of electrokinetic flows

This paper presents a numerical framework for design-based analyses of electrokinetic flow in interconnects. Electrokinetic effects, which can be broadly divided into electrophoresis and electroosmosis, are of importance in providing a transport mechanism in microfluidic devices for both pumping and separation. Models for the electrokinetic effects can be derived and coupled to the fluid dynamic equations through appropriate source terms. In the design of practical microdevices, however, accurate coupling of the electrokinetic effects requires the knowledge of several material and physical parameters, such as the diffusivity and the mobility of the solute in the solvent. Additionally wall-based effects such as chemical binding sites might exist that affect the flow patterns. In this paper, we address some of these issues by describing a synergistic numerical/experimental process to extract the parameters required. Experiments were conducted to provide the numerical simulations with a mechanism to extract these parameters based on quantitative comparisons with each other. These parameters were then applied in predicting further experiments to validate the process. As part of this research, we have created NetFlow, a tool for micro-fluid analyses. The tool can be validated and applied in existing technologies by first creating test structures to extract representations of the physical phenomena in the device, and then applying them in the design analyses to predict correct behavior.

System Design of Two Dimensional Microchip Separation Devices

Two dimensional (2D) separation systems have been used extensively for the analysis of complex protein and peptide mixtures because of the increased peak capacity they provide relative to one-dimensional separations [1,2,3,4,5]. The effects of miniaturization of various separation schemes have been reported by Manz et al [6], In general, miniaturization has been shown to provide high separation efficiencies and a convenient means of manipulating extremely small sample volumes. Recently, microscale 2D systems using micellar electrokinetic chromatography (MEKC) with capillary electrophoresis (CE) and open channel electro chromatography (OCEC) with CE have been reported [7,8]. In this paper, we will demonstrate the use of CAD software for predictive design of 2D microchips, using both detailed simulation for optimization of electrophoretic injections and turn designs, as well as reduced order modeling to better understand system performance trade-offs. Modeling results will be compared against experimental observations by Ramsey et al [7, 8].