Integrating Coherent Porous Silicon as a Wicking Structure in the MEMS Based Fabrication of a Vertically Wicking Micro-Columnated Loop Heat Pipe

System design, component-wise fabrication and experimental thin-film evaporation results are presented for a vertically wicking micro-columnated loop heat pipe. Designed for fabrication using a three-layer wafer stack, this MEMS phase change device has components etched on both sides of the middle silicon wafer that are sealed by thinner top and bottom capping wafers. A coherent porous silicon (CPS) based dual-scale micro-columnated wick design uses a primary wick for capillary pumping and a secondary surface-micro-textured wick for thin-film liquid evaporation. For etching CPS, a Teflon based wafer-level electrochemical etching setup is implemented and results from a preliminary die-level etching study are reported. The main device components, which include the fluid transport channels, the condenser section and the columnated vapor chamber in a non-CPS base, are fabricated on silicon wafers using standard MEMS fabrication techniques. Thermal experiments are performed to study the phenomena of thin-film evaporation in a columnated open-loop micro evaporator.