Nature-Inspired Bubble Magnetic Microrobots for Multimode Locomotion, Cargo Delivery, Imaging, and Biosensing

Wirelessly actuated magnetic microrobots are promising tools in medical applications due to their tiny sizes and attractive robotic properties. However, it remains a huge challenge to integrate sufficient functionalities in a limited volume. Microscopic natural phenomenon is a great reference for current microrobot design, where the underlying intelligence and subtlety spurs related modern artificial systems. Inspired by air bubbles in nature, herein, we report a kind of novel magnetic air bubble microrobots. The air bubble- based structure enables multiple functionalities including cargo delivery, multimode locomotion, micromanipulation, medical imaging, and biosensing. The proposed microrobot is essentially Pickering bubbles composed of magnetic particles and air bub- bles. Their hollow structures help produce lighter microrobots with density less than 1 g/cm3, enabling buoyancy-based self- propulsion. Buoyancy and magnetic forces actuation enables flexible 3D locomotion in fluidic environments. Experimental results show that the microrobots can be controlled properly for designated assignments. Furthermore, the introduction of air bubble enhances ultrasound imaging, facilitating further in vivo applications. These findings offer a significant microrobot design paradigm by exploiting natural physical intelligence at the small scale.