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

Abstract

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/V 2 with a FET's ratio of ∼19. The device will consume less power as the gate to source voltage (V GS) 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. © 2006 IOP Publishing Ltd.