School of Mechanical Engineering and Automation, Beihang University, Beijing 100191, P. R. China.
Soft Matter. 2017 Aug 16;13(32):5381-5388. doi: 10.1039/c7sm01205e.
Spherical-cap-shaped interfacial nanobubbles (NBs) forming on hydrophobic surfaces in aqueous solutions have extensively been studied both from a fundamental point of view and due to their relevance for various practical applications. In this study, the nucleation mechanism of spontaneously generated NBs at solid-liquid interfaces of immersed nanostructured hydrophobic surfaces is studied. Depending on the size and density of the surface nanostructures, NBs with different size and density were reproducibly and deterministically obtained. A two-step process can explain the NB nucleation, based on the crevice model, i.e., entrapped air pockets in surface cavities which grow by diffusion. The results show direct evidence for the spontaneous formation of NBs on a surface at its immersion. Next, the influence of size and shape of the nanostructures on the nucleated NBs are revealed. In particular, on non-circular nanopits we obtain NBs with a non-circular footprint, demonstrating the strong pinning forces at the three-phase contact line.
球形帽状界面纳米气泡（NBs）在水溶液中形成于疏液表面，从基础观点和实际应用角度均受到了广泛研究。在这项研究中，研究了浸入式纳米结构化疏液表面固液界面上自发生成 NBs 的成核机制。根据表面纳米结构的大小和密度，可以可重复且确定地获得具有不同大小和密度的 NBs。基于缝隙模型，可以解释 NB 成核的两步过程，即表面腔中的被困空气口袋通过扩散而生长。结果为表面在浸入时自发形成 NBs 提供了直接证据。接下来，揭示了纳米结构的大小和形状对成核 NBs 的影响。特别是，在非圆形纳米凹坑上，我们获得了具有非圆形足迹的 NBs，证明了三相接触线上的强钉扎力。
