A dielectric liquid contact thermal switch with electrowetting actuation

• Published in: Journal of micromechanics and microengineering 2011-10, Vol.21 (10), p.104009-12
• Main Authors: McLanahan, A R, Richards, C D, Richards, R F
• Format: Article
• Language: English
• Subjects: Condensed matter: structure, mechanical and thermal properties; Contact; Dielectrics; Exact sciences and technology; Heat transfer; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Liquids; Mechanical instruments, equipment and techniques; Micromechanical devices and systems; Physics; Solid-fluid interfaces; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Switches; Switching; Thermal resistance; Thin films; Wetting
• ISSN: 0960-1317; 1361-6439
• DOI: 10.1088/0960-1317/21/10/104009

We present the design, fabrication and characterization of a new kind of MEMS thermal switch based on electrowetting actuation of a dielectric liquid contact. The thermal switch consists of a thin layer (30-120 mu m thick) of a dielectric liquid, such as glycerin or water, squeezed between two silicon dies. The gas pressure in the gap can be varied from ambient down to 0.6 T. The switch operates by changing the conductive path between the two silicon dies by moving the thin layer of dielectric liquid using electrowetting. The result is a bi-stable thermal switch that can change between a low thermal resistance state and a high thermal resistance state. Electrowetting measurements indicate switching time on the order of 2-40 s with switching time increasing as gap width decreases. The power required to switch states is less than 2 mW. Heat transfer measurements indicate thermal resistance ratios of up to R sub(OFF)/R sub(ON) = 14, with the highest thermal resistance ratios found for the smallest gap (30 mu m) and the lowest pressure (0.6 T).