摘要
This paper presents a newly developed thermally driven normally-closed microvalve with fast switch-on capability and a backpressure resistance that can be specified by the designer. Two key components are involved in this micromachined valve: (1) an upper elastic blockade with stiffness adjustability; (2) a lower 3-dimensional microheater with rapid heating rate. During actuation, volume expansion of paraffin wax inside the microheater forms micro-bulges that protrude through holes in the top wall of the paraffin's encapsulation. The protruding micro-bulges lift the valve blockade, allowing fluid to pass. When power to the microheater is turned off, the paraffin cools and valve returns to its normally closed state. Based on a design capable of 25 kPa backpressure, the valve attains its fully open state within 0.125 s under either a 3 V or 6 V battery-powered supply. When heating power is turned off, the valve returns to its fully closed state within 3.5 s. Details of fabrication, characterization and a discussion are presented in the text. © 2010 Elsevier B.V. All rights reserved.