Crucial Role of an Aerophobic Substrate in Bubble-Propelled Nanomotor Aggregation.

In bubble-propelled autonomous micro/nanomotors, the solid−liquid contact interface plays a crucial role in bubble detachment, which in turn is a key factor in achieving effective propulsion. Modifying the liquid phase by adding a surfactants is a common methods to improve propulsion, but it has several disadvantages. For example, we have found that, under these conditions, the long-term retention of bubbles will cause a decrease in solid−liquid contact area and catalytic activity. Here, the use of a 'superaerophobic' solid phase is tested as an efficient means to solve this challenge. In this study, we prepared a single-sided Ti/TiO2-Pt nanowire network and, thus, constructed a bubble-propelled micro/nanomotor network. In comparison to an underwater aerophilic substrate loaded with Pt, in which bubbles are strongly held on the surface, the Ti/TiO2-Pt nanowire network showed good aerophobicity. In particular, after UV illumination for 30 s, the substrate became superaerophobic, which promoted the release of O2 bubbles. The results of this study reveal how to modify the detachment behaviour of bubbles by controlling the aerophobic behaviour of solid surfaces of autonomous micro/nanomotors in an aqueous medium.