3. Conclusion
A magnetic field-actuated liquid metal-based droplet robot was designed and developed that can be applied for reconfigurable and transient electronics, i.e., as a remote-controlled circuit switch. These robots comprise of the liquid metal and the magnetic particle iron pentacarbonyl. Upon exertion of an external magnetic field (by a permanent magnet), the magnetic liquid metal-based soft robot can undergo reversible elongation, bending, and on-demand locomotion. Programmable shape encoding of the liquid metal robots and the phase transition of the robot between liquid and solid states can be utilized to fix a desired shape via ice cooling and infrared light irradiation. Furthermore, on-demand merging and splitting up of the soft robots can be achieved by controlling the direction and shape of the electric field. The on-demand elongation and bending of the soft robots was used in a dynamic and recyclable switch in a complex circuit. Compared with traditional miniature electronic switches, the liquid metal droplet robot enables simple and remote control of the complex circuits in a reconfigurable manner, which effectively simplifies the circuit layout. In addition, the liquid metal soft robot can be removed and recycled by removing the robot with the help of the magnetic field. In this case, the open circuit is regained together with the reusable soft robot. Besides, multiple liquid metal droplet robots can repair damaged sections of microcircuits by remote actuation, controllable coalescence, and on-demand circuit welding. The technology provides a new application scenario of droplet-based soft robots for on-demand circuit welding and transient recyclable electronics.