Coherent macro porous silicon as a wick structure in an integrated microfluidic two-phase cooling system

The previous papers presented at STAIF 2002 and STAIF 2003 discussed the design, fabrication and characterization of the evaporator section and the initial test cell of a planar MEMS loop heat pipe based upon coherent porous silicon or "CPS" technology. The potentially revolutionary advantage of CPS technology is that it is planar and allows for pores or capillaries of absolutely uniform diameter. Coherent porous silicon can be mass-produced by various MEMS fabrication techniques. The preliminary experiments made with the original test structure exhibited the desired temperature and pressure differences, but these differences were extremely small and oscillatory. This paper describes modifications made to the initial test cell design, which were intended to improve its evacuated, closed loop performance. Included among these changes were the redesign of the compensation chamber and condenser, an increase in the porosity of the coherent porous silicon wick, the fabrication of silicon top "hot" plates with an increased depth of the vapor reservoir and the integration of metal resistive heater elements onto the backside of the top plates to simulate the input heat. Some changes were made in the test sequence to produce more discernable differences in temperatures and pressures. The most recent results of the tests made with the modified system will be presented.

Section: The Primary Coherent Porous Silicon Wickmentioning

confidence: 99%

The MEMS Loop Heat Pipe Based on Coherent Porous Silicon — The Modified System Test Structure

Cytrynowicz¹,

Medis²,

Parimi³

et al. 2004

“…The basic porosities of the arrays were twenty-five percent Critical Current (5µm@10µm, 2µm@4µm and thirty-nine percent (5µm@8µm). The theoretical upper limit to porosity is ninety-two percent, which is achievable through various post-processing techniques (Hölke, 1998;Mantravadi, 2000;Rajaraman, 2000;Ranganathan, 1999;Van Dyke, 2000). At present pores are patterned over the entire wafer surface.…”

Section: The Coherent Porous Silicon Wickmentioning

confidence: 99%

Test Cell for a Novel Planar MEMS Loop Heat Pipe Based on Coherent Porous Silicon

Cytrynowicz¹,

Hamdan²,

Medis³

et al. 2003

Work towards the development of an innovative, potentially high power density, MEMS loop heat pipe is in progress at the Center for Microelectronic Sensors and M E M S at the University of Cincinnati. The design of the loop heat pipe is based upon the very unique coherent porous silicon technology, a technique in which vast arrays of micrometer-sized through-holes are photo-electrochemically etched into a silicon wafer perpendicular to the (100) surface. The initial mathematical model, the design, fabrication and characterization of the device in the open loop configuration were previously reported at this conference, STAIF 2002. This paper begins with a very brief explanation of the device and its theory of operation. The design of the device components and their production utilizing the various techniques of microelectronic and microelectromechanical fabrication are presented. The modifications made to the photon-induced, electrochemical etch process, which significantly increase the etch rate of the pores, are explained. Attention is given to the mathematical model of the planar, MEMS, loop heat pipe with respect to the generation of the dimensions of the components through a summary of the recent advances. The emphasis of this paper is upon the design, construction and the characterization of the evacuated closed loop test cell structure. GENERAL DESCRIPTION OF THE MEMS LOOP HEAT PIPE FIGURE 1. This is a schematic representation of the MEMS loop heat pipe and its components.

“…The technique was extended and applied by H. T Henderson's group at the Center for Microelectronic Sensors and MEMS at the University of Cincinnati. Pore diameters achieved range between one and 35 micrometers and pore pitch ranges between four and 100 micrometers (Hölke et al, 1998, Rajaraman, 2000. Henderson's group at the University of Cincinnati is also investigating coherent porous silicon for use as micro-needles, gas discharge lamps, and other microfluidic systems such as "chemistry laboratory on a chip" devices (Ranganathan, 1999, Rajaraman, 2000, Mantravadi, 2000, Van Dyke, 2000.…”

Section: The Coherent Porous Silicon Wickmentioning

confidence: 99%

MEMS loop heat pipe based on coherent porous silicon technology

Cytrynowicz

Hamdan

Medis

et al. 2002

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