Bubble-based microrobot: Recent progress and future perspective

In recent years, microbubbles, as a new tool to operate in microfluidic chips, have attracted more and more attention due to their good biocompatibility, convenient manufacture, and easy manipulation. As the core part of microfluidic operation, microbubbles can be considered as a robot to complete the operation of micro-scale objects. In this review, we first introduce various methods of manufacturing bubbles, and discuss the differences in properties and morphology of bubbles. Then, according to the different driving forms and applications of microbubbles, we classify microbubbles into photothermal bubble microrobots, acoustic oscillation bubble microrobots and Janus bubble micromotors. We make a concrete theoretical analysis of how these three modules realize movement and how to push or capture micro-particles, and introduce various applications of bubble microrobots. At last, we summarized some challenges faced by bubble microrobots, put forward some bottleneck problems that need to be broken urgently, and looked forward to the development trend of bubble microrobots in the future.