Experimental investigation and modelling on the water ingress protection of laser-structured glass-micromesh chips with cloverleaf-like microstructures
Glass-micromesh chips, produced by a laser-induced deep etching (LIDE) technique, have recently been demonstrated as promising environmental protective components for microelectromechanical system (MEMS)-based microphones, exhibiting minimal adverse impact on their acoustic characteristics and a high capability to filter solid particles. However, their potential to prevent water penetration into the sensor system has not been fully explored. Here, we investigate the water ingress and breakthrough protection of these glass-micromesh chips by conducting analytical modeling, surface wetting experimental measurements, liquid-gas interface evolution studies in microcavities based on computer simulations, and direct experimental measurements to elucidate water-penetration-related key factors. Experimental measurements of the breakthrough critical pressure using a custom-designed apparatus yield (27.4 ± 0.6) mbar and (13 ± 1) mbar for micromesh chips with an advancing water contact angle of (59 ± 2)° on planar glass and side dimensions of 76 µm and 136 µm, respectively. These results are in excellent agreement with computer simulations using a phase-field method, which in turn can be rationalized with a simple analytical model. Both the simulations and analytical modeling allow us to predict the effects of the micromesh geometry and wettability across their whole range of parameter space. The findings demonstrate that, with suitable design, a hydrophilic material like glass can effectively withstand significant external water pressure. Moreover, the experimental and computational methodologies developed here can be applied to numerous related challenges involving ingression and breakthrough pressures in complex geometries, including for water-oil separation, superomniphobic surfaces, and liquid diodes.