Diffusively Controlled Growth of Nanobubbles under Contact Line Pinning: Implication of Nanoscale Flow and Heat Controls by Nanobubbles

More and more micro/nanofluidic devices are proposed to improve the performance in thermal and medical applications, and nanobubbles promise a new way of controlling the heat and flow at high spatial and temporal resolutions. The long lifetime of static nanobubbles has been extensively investigated in both experiments and theoretical modeling, but the dynamic growth of nanobubbles lacks comprehensive understanding. Therefore, we conduct an experimental investigation of nanobubble growth in a graphene liquid cell, under oversaturation conditions of dissolved hydrogen gas by electron beam radiolysis of water, via in situ transmission electron microscopy (in situ liquid cell TEM). We analyze characteristic parameters of nanobubble growth, including radius, volume, extension length, nanobubble shape, contact angle, and growth rate, based on the TEM images. We demonstrate that the growth of individual nanobubbles is determined by the oversaturation level of dissolved gas and follows a diffusively controlled dynamic as described by the Epstein–Plesset model. With the information from 3D reconstruction of nanobubbles, we reveal that both growth rate and local contact angle are affected by contact line pinning. Overall, we present a comprehensive analysis of a diffusively controlled nanobubble growth subjected to dissolved hydrogen gas concentrations and contact line pinning through the growth rate, nanobubble shape, and contact angle.