Multimodal Bubble Microrobot Near an Air–Water Interface

Abstract The development of multifunctional and robust swimming microrobots working at the free air–liquid interface has encountered challenge as new manipulation strategies are needed to overcome the complicated interfacial restrictions. Here, flexible but reliable mechanisms are shown that achieve a remote‐control bubble microrobot with multiple working modes and high maneuverability by the assistance of a soft air–liquid interface. This bubble microrobot is developed from a hollow Janus microsphere (JM) regulated by a magnetic field, which can implement switchable working modes like pusher, gripper, anchor, and sweeper. The collapse of the microbubble and the accompanying directional jet flow play a key role for functioning in these working modes, which is analogous to a “bubble tentacle.” Using a simple gamepad, the orientation and the navigation of the bubble microrobot can be easily manipulated. In particular, a speed modulation method is found for the bubble microrobot, which uses vertical magnetic field to control the orientation of the JM and the direction of the bubble‐induced jet flow without changing the fuel concentration. The findings demonstrate a substantial advance of the bubble microrobot specifically working at the air–liquid interface and depict some nonintuitive mechanisms that can help develop more complicated microswimmers.