Yibo Wu

Design and implementation of a bistable microcantilever actuator for magnetostatic latching relay

This paper presents the design, fabrication, and implementation of a microcantilever actuator with magnetostatic latching for performing low power bistable relay applications. This unique bistable feature consists of a low-stiffness torsion/cantilever beam system with circular-shaped support and a permanent magnet for holding the closed state with a permalloy soft magnetic circuit. The special circular support is designed to enhance the stiffness of the overhang beams. First, mechanical modeling of the leveraged torsion/cantilever beams was performed by Castiglianos theorem so as to deduce the spring stiffness of system. Then the device has been prepared by a laminated photoresist sacrificial layer process (LPSLP). Finally, mechanical performance was characterized by atomic force microscopy (AFM), combined with finite element simulation using ANSYS(TM) package and analysis model as well. Switching between two stable states of the microactuator was successfully validated with WYKO NT1100 optical profiling system.

Vertically bidirectional bistable microrelay with magnetostatic and thermal actuations

The design and characterization of a novel bidirectional bistable MEMS relay with out-of-plane motion are presented in this paper. The microrelay is actuated vertically by combining with magnetostatic and electrothermal microactuators. This bistability features a permanent magnet actuation without electromagnetic coils where lower power consumption is requested. The device was fabricated by laminated sacrificial thick copper layer process in UV-LIGA. The mechanical performance was characterized using atomic force microscope (AFM) as well as nano indentation tester. Switching between two stable states of the fabricated bidirectional bistable microrelay was successfully validated with WYKO NT1100 optical profiling system.

Torsion/cantilever-based MEMS bistable mechanisms with different support configurations: structure design and comparison

Three types of torsion/cantilever-based MEMS bistable mechanisms (BMs) with different support configurations have been constructed, modeled and experimented. For the support configuration, there is a crisscross-shaped, a ring-shaped and a diamond-shaped support beam, respectively. The proposed MEMS BMs consist of a free–free torsion-based cantilever which forms a symmetrical rocker lever. The free–free cantilever is suspended by a support skeleton which in turn is attached to a torsion cantilever. A permanent magnet is attached beside for holding the closed state with a permalloy soft magnetic circuit. The different special support configurations account for a low torsional compliance with the overhanging beams. In order to deduce the equivalent stiffness coefficient of BM systems, mechanical modeling of three types of torsion/cantilever-based MEMS BMs was performed by the classical beam theorem. Meanwhile, the magnetostatic latching force was also deduced by the Maxwell electromagnetism theory. The performances of these MEMS BMs have been compared by the evaluation of static deformation variations, equivalent stiffness coefficients and dynamical switching characterizations. Finally, mechanical performance was characterized by atomic force microscopy, combined with a Nanoindentation Tester. In addition, bistabilities of the MEMS BMs were proved by theoretical analysis as well as experimental results. Among these BMs, the ring-shaped MEMS BM is extremely prone to deflect due to relatively low stiffness compared with other types. The torsion/cantilever-based MEMS BMs have potential application in the field of latching relays with low power consumption.

A latching bistable microswitch using dual-beam electrothermal actuation

This paper reports on design and mechanical characteristic of a latching bistable microswitch with a dual-beam electrothermal actuator. As designed two novel contact pair, a stable state can be acquired without continuous power. The bistable mechanical characteristic of the switch is measured by a bonding strength tester. Testing results are in good agreement with theoretic analysis. The optical micrographs clearly indicate that the switch can stay latched in its two states. This novel design provides an excellent alternative for power and communication applications.

An electro-thermal SU-8 cantilever micro actuator based on bimorph effect

An electro-thermal SU-8 cantilever micro actuator with large vertical motion at low voltage is presented in this paper. It is lower in voltage due to employing SU-8 as functional material because of its high coefficient of thermal expansion. A finite element simulation was utilized to determine the optimal parameter. Windows in the center of cantilever can reduce internal residual stress. And we also added a nickel matrix on surface of support base to enhance bonding force between supportive base and driving section. Then actuators were obtained through Micro Fabrication Technology. Finally the Scanning-electron microscope and WYKO NT1100 optical profiling system demonstrated that the electro-thermal actuator possesses a high quality cantilever. Its stiffness is relative large that is sufficient for application in Micro device proved by Bonding Tester. With applied voltage 0.5V the electro-thermal actuator can generate a vertical displacement of 42.9μm.

Modeling of a bistable MEMS mechanism with torsion/cantilever beams

A mechanical modeling of a novel bistable MEMS mechanism with a torsion/cantilever beam system is presented in this paper. The model includes mathematical solution to the system equivalent stiffness, and simulating analysis for the deformation under load. Meanwhile, the geometrical parameters of bistable system were optimized with Matlab software. And the optimization dimensions involves the length, width and thickness where l<inf>1</inf>=1130µm, w<inf>1</inf>=100µm, t<inf>1</inf>=10µm for cantilever, and l<inf>2</inf>=500µm, w<inf>2</inf>=20µm, t<inf>2</inf>=10µm for torsional flexure, respectively. In addition, modal analysis was performed to determine the nature frequency of the torsion/cantilever beam system. The first four fundamental resonant modes consist of torsional, out-of-plane sliding, in-plane sliding and out-of-plane rocking mode. This proposed bistable mechanism can be suitable for bistable switching relay applications where low power consumption is requested.

Design optimization of polymeric Out-of-plane electro-thermal actuator

In this paper, we report the design, simulation and optimization of a novel polymeric out-of-plane electro-thermal micro-actuator. The electro-thermal micro-actuator consists of tri-layers: the passive Ni layer, an expanding SU-8 layer and a curling S-shaped Ni heater. The tri-layer actuator is accompanied with a suspended structure to produce an out-of-plane movement perpendicular to the substrate, under a pulse current. Firstly, this proposed device is advanced. By means of FEA (finite element simulation with ANSYS™), the geometric structure is optimized and the electro-thermal capabilities are determined theoretically. The simulation shows the actuator can obtain the best capabilities, when the thickness of actuating SU-8 layer is 12μm; the thicknesses of the heating layer and passive Ni layer are all 4μm.