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In Situ Observation of Dynamic Wetting Transition in Re-Entrant Microstructures
Yang He1, Qingqing Zhou1, Shengkun Wang1
1Key Laboratory of Micro/Nano Systems for Aerospace, Ministry of Education and Shaan'xi Key Provincial Laboratory of Micro and Nano Electromechanical Systems, Northwestern Polytechnical University , Xi'an 710072, P. R. China.
Abstract:
Re-entrant microstructures exhibit excellent wetting stability under different pressure levels, but the underlying mechanism determined by wetting transition behavior at the microscale level remains unclear. We propose the "wetting chip" method for in situ assessment of the dynamic behavior of wetting transition in re-entrant microstructures. High sag and transverse depinning were observed in re-entrant microstructures. Analysis indicated that high sag and transverse depinning mainly influenced the stability of the structures. The threshold pressure and longevity of wetting transition were predicted and experimentally verified. The design criteria of wetting stability, including small geometry design, hydrophobic material selection, and sidewall condition, were also presented. The proposed method and model can be applied to different shapes and geometry microstructures to elucidate wetting stability.