Abstract: Microfludic inertial switch with integrating sensing and actuating functions has drawn the increasing attention. In design, adjusting the contact angle between the fluid and the wall of the microchannel is able to adjust the threshold of the microfluidic inertial switch and improve its sensitivity. As to Galinstan-based microfluidic inertial switch, the super lyophobic surface of polymethyl methacrylate(PMMA) has been prepared by etching-phase separation method, where chemical etching, phase separation and SiO₂ deposition prompts the formation of the hierarchical surface roughness with PMMA-SiO₂. The influences from recipe, proportion of ingredients and process are studied by using optical microsocope, scanning electron microscope(SEM), atomic force microscope(AFM) and infrared spectrometer. It is found that that, when the solvents are prepared as C₄H₈O to C₂H₅OH as 1:1 in volume ratio and the SiO₂content is 15 mg/mL, the optimized surface roughness is obtained. In final, the threshold of microfluidic inertial switch is improved from 52.52g to 28.62g, in matching with the requirements of the mercury-based switch.

Key words: super lyophobic, surface modification of PMMA, etching-phase separation, microfluidic inertial switch