Microstructures on boiling surfaces had been adopted to study heat transfer enhancement mechanism because of its controllability of precise geometries by MEMS techniques. In addition, several bubble-inducing surfaces such as porous or hydrophobic surfaces were verified to be combined with microstructures for further enhancement of cooling efficiency. In this research, microstructures with porous and dual-wettability (Janus) were fabricated by soft-lithography with replicating molds. In saturated pool boiling at atmospheric pressure, the porous and Janus microstructures increased the heat transfer coefficient by 50% over that of plain-cylindrical microstructures. The increase occurred because the porous and wettability-controlled structures favored vigorous bubble generation, and supported high contact line density, which is strongly related to effective cooling through the near-bubble region.

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