Design of Two-Link, In-Plane, Bistable Compliant Micro-Mechanisms

Abstract

A bistable mechanism has two stable states within its range of motion. Its advantages include the ability to stay in two positions without power input and despite small external disturbances. Therefore, bistable micro-mechanisms could allow the creation of MEMS with improved energy efficiency and positioning accuracy. This paper presents bistable micro-mechanisms which function within the plane of fabrication. These bistable mechanisms, called “Young” bistable mechanisms, obtain their energy storage characteristics from the deflection of two compliant members. They have two pin joints connected to the substrate, and can be constructed of two layers of polysilicon. The pseudo-rigid-body model is used to analyze and design these mechanisms. This approach allows greater freedom and flexibility in the design process. The mechanisms were fabricated and tested to demonstrate their bistable behavior and to determine the repeatability of their stable positions.

Optimal design of a bistable switch

“…The advantage of this switch over other alternatives (17)(18)(19)(20) is that it uses no latches, hinges, or residual stress to achieve its bistability.…”

Introduction to Compliant Mechanisms

“…Advantages include that a compliant element integrates both a spring and hinge function into a single component providing a "home" position where the device will go when unloaded. This integration also allows certain behaviors, such as bistability (the characteristic of having two distinct preferred positions, such as the on-off positions of a light switch) [9]. However, there are times when these qualities are not desired, and the properties become a disadvantage in the device design.…”

Modeling of large-deflection links for compliant mechanisms

“…Compared with conventional rigid-body mechanisms, compliant mechanisms have many advantages in cost-reduction and performance-improvement such as part-count reduction, reduced assembly time, simplified manufacturing processes, reduced friction, wear, backlash and noise [1]. Therefore, compliant mechanisms have wide applications in the light-micro field, especially for a micro-electro mechanical system (MEMS) [2].…”