Many studies have investigated boiling heat transfer in microchannels; however, such phenomena are not yet fully understood, and conflicting results have been reported. There are many important parameters that govern behavior in microsystems, including channel shape, roughness, and choice of material. One potentially important parameter is hydrophobicity of the microchannel surface, as interfacial forces play an increasing role at microscales. We developed a new method of fabricating a single glass rectangular microchannel and microheater using the MEMS (Micro-Electro-Mechanical System) fabrication technique. The glass was used as a hydrophilic surface, and a self-assembled monolayer was coated with OTS (Octadecyl-Trichloro-Silane) to obtain a hydrophobic surface. We conducted an experiment of boiling heat transfer in a microchannel using two surfaces of contrasting hydrophobicity. The resulting flow was observed using a long-distance microscope and a high-speed camera. This approach enables a qualitative analysis of the hydrophobicity effect on the flow regime.

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