Pump-valve dual-functional liquid metal soft actuators

Abstract

Soft actuators offer several advantages over traditional rigid machines. Among soft materials, liquid metal (LM) is particularly noteworthy for its electro-responsive surface properties that induce flow or morphological changes, making it ideal for soft machines. Although using LM droplets as micropumps is simple, they face challenges in efficient vertical fluid pumping. Here, we report a pump-valve dual-functional LM soft actuator (PDLMA) that can continuously pump liquid upward. Benefiting from the unique conformability of LM, the PDLMA can provide the function of a check valve, which blocks the backflow of the rising liquid while continuing the pumping effect. At 6 V direct current (DC), the PDLMA lifts the solution more than 80 cm. We demonstrate the device’s applications in circuit-on/off switches and pump-mixer systems. Moreover, as a conceptual experiment, we show the PDLMA’s ability to achieve contamination-free drug delivery. The PDLMA represents a crucial step toward the development of soft actuators for flexible machines.