Andojo Ongkodjojo

Global optimization and design for microelectromechanical systems devices based on simulated annealing

In this paper, we propose a new method of global optimal design with simulated annealing (SA) for microelectromechanical systems (MEMS) devices. The optimal design of MEMS devices, with a microgyroscope as our device example, has been carried out to find the maximum sensitivity satisfying constraints imposed by functional and geometrical constraints. The optimization algorithm (SA) used is essentially an iterative random search procedure with adaptive moves along the coordinate directions. It permits downhill moves under the control of a probabilistic criterion, thus tending to avoid the first local maxima encountered. The optimization results are verified and validated with the finite element method (FEM) and the boundary element method (BEM) IntelliSuite™ results and measured data. When compared with Microsoft Excel Solver™ (generalized reduced gradient algorithm), our SA-based optimization approach exhibits promising superiority, and finds the global solution easily. There is also good agreement among the numerical computation results generated by the SA algorithm, the simulation results generated by IntelliSuite™, and the measured data.

Optimized design of a micromachined G-switch based on contactless configuration for health care applications

This paper proposes design concept and fundamentals of a novel acceleration microswitch (G-switch), which is an integration of bimorph actuator and field effect transistor (FET). This micro-switch can be used to actuate the alarm system for call for helps - minimizing injuries after the fall among elderly; or trigger the air-inflatable hip protector for the fall prevention. The device can be attached to the developed MEMS-Wear smart shirt. Its structural design and switching FET are optimized using the global optimization method so that the bimorph as a movable gate can collapse on the gate insulating layer, when there is an impact force, which is greater than a threshold value (experimentally found to be 4.8g based on the previously published report). This contactless mechanism optimizes the field effect between the bimorph and the substrate causing an electrical current flow profusely with a sensitivity of 0.1 mA/V2 with a FETs ratio of ~19. The device will consume less power as the gate to source voltage (VGS) can be applied up to 4 V. All design parameters must satisfy the specified design constraints. In future, the optimized design will be fabricated and incorporated into the smart shirt for testing upon the fall events.

SLIDE FILM DAMPING AND SQUEEZE FILM DAMPING MODELS CONSIDERING GAS RAREFACTION EFFECTS FOR MEMS DEVICES

Slide and squeeze film damping models play important role in the dynamics of the micro-electro-mechanical systems (MEMS) devices as they are important design parameters, which significantly affect the frequency-domain behavior and the quality factor (Q-factor) of the vibrating MEMS devices for both lateral and vertical motions. For ensuring the accuracy of the damping models, gas rarefaction effects was considered thoroughly by introducing an effective viscosity (ηeff) into our models. As the effective viscosity of the gas is a key parameter of our damping models, it is very important to approximate the parameter with the measurement data using the Simulated Annealing (SA) algorithm. Our results show that the discrepancies of both the slide and squeeze film dampings are less than 0.26% with the measurement data for an applied pressure (pa<0.1 Pa), and less than 0.33% for an applied pressure (1 Pa≤pa≤50 Pa).

Overview of MEMSWear II - Incorporating MEMS Technology into smart shirt for Geriatric care

This paper presents a method of using smart sensors for continuous detection of vital physiological and physical gait signals that can be relayed to a fall prediction algorithm for predicting an imminent faint fall. A novel MEMS based BP sensor will be discussed briefly. Once an imminent faint fall is detected, fall prevention and injury minimization devices will be activated. A body area network consisting sensor circuits utilizing short range ISM communication will be used to enable signal transmission to a processor which acts as a communication gateway as well. This processor would then encode and send the signals via Bluetooth to designated devices to effect inform caregivers or family members.

Techniques in Global Optimal Design for MEMS & Their Applications

This chapter presents an overview on techniques in global optimal design for MEMS & their applications. We address single-objective and multi-objective functions optimizations using a Simulated Annealing (SA) method, which has been used by us to handle some constraints as well. This optimization method is essentially an iterative random search procedure with adaptive moves along the coordinate directions. It permits downhill or uphill moves under the control of a probabilistic criterion using Metropolis criterion. Thus, it tends to avoid the first local maxima or minima encountered. The SA method is usually used for a single objective optimization. However, the use of the SA for multi-objective functions is also described in this chapter. Besides, the evolutionary algorithms, which are widely used for multi-objective problems, are briefly presented. For design applications, our device example is a multimorph. The SA exhibits a promising superiority over other algorithms using the gradient methods, have a greater search flexibility and efficiency in exploring the neighborhood of the solutions on the constraints boundaries to find the global optimum solutions. In fact, the SA has potential solutions in the multi-objective optimization field.

Characterizations of micromachined devices using planar motion analyzer (PMA)

In this paper we illustrate the capabilities of the planar motion analyzer (PMA) with a study of the dynamic and static behavior of a micromachined structure. Both static and dynamic characterizations and measurement settings are also demonstrated. The optical measurement system uses the laser vibration measurement technique for imaging; and then measuring the lateral resonant frequency and sensor displacements as well. The PMA analyzes in-plane vibrations of a MEMS device under a clear microscope. Its working principle is based on the stroboscopic principle. Based on this principle, characterization results in both time and frequency domains can be accurately generated and analyzed. Our device example for the measurement is a tunneling-based microresonator, which was fabricated using the backside released SOI (BARS) process. The lateral moving proof mass is suspended by the folded springs, and its tip protrudes to an opposing electrode by means of electrostatic forces

Self-Assembled Monolayers (SAM) for Tunneling Sensors

In this research, we explore the use of SAM (Self-Assembled Monolayers) materials for improving the robustness of a tunneling accelerometer. For gold coated tip-gold sample, the results are comparable with expectations for tunneling between gold electrodes in air. Using SAM materials, the robustness of the tunnel tips in terms of reliability shows promise of improved characteristics.