Liquid metal droplet robot

Abstract Liquid metal (LM) droplets made from gallium-based alloys exhibit excellent biomimetic locomotion and deformation capabilities under external stimulating fields and have presented potentials in a variety of applications. However, its application in robotics is presently hampered by limited maneuverability in two-dimensional (2D) space and weak cargo carrying capacity. Here, we propose a composite liquid metal droplet robot (LMDR) which appears as a LM droplet but exhibits an extraordinary actuating performance in 3D space. The LMDR is fabricated by assembling a hollow and spherical-shaped magnetic internal framework (IF) into a LM droplet, and the IF can be disassembled from the LM droplet with the application of an external magnetic field. The maneuver of the LMDR is realized using the interplay of electric and magnetic fields, and complex actuation especially jumping to avoid obstacles, climbing steep slopes, and rotating its body to the desired posture can be achieved. The hollow IF within the LMDR has a cargo carrying capacity and we demonstrate a proof-of-concept experiment to show the transportation and controlled release of a chemical indicator using the LMDR. More importantly, an in vitro targeted drug delivery and therapy trial to treat breast cancer cells (4T1) with a drug loaded LMDR is also successfully performed. The demonstrated capabilities of the LMDR present a promising potential in developing future targeted drug delivery and soft robotic systems with high controllability and multi-functionalities.