Electrochemically controllable actuation of liquid metal droplets based on Marangoni effect

Liquid metal droplets immersed in an alkaline electrolyte undergo various deformations and movements after a driving voltage is applied. However, interference with the electrolyte severely restricts further applications. In this study, a novel approach using the Marangoni effect is introduced to control the actuation of the liquid metal and overcome existing limitations. First, the linear movement of the liquid metal droplets on various substrates, including paper and cloth saturated with an NaOH solution and glass wetted with an NaOH solution, is characterized. The reciprocating movement can be precisely controlled by modulating the amplitude and the frequency of the driving voltage. In addition, the liquid metal droplet can move along an NaOH solution path with complex shapes and have a self-correction ability to move along the desired route. Finally, the unique actuation of the liquid metal droplet based on the Marangoni effect is applied to electronic switches and microvalves. The experimental results show that the liquid metal droplets using the Marangoni effect open new avenues for soft actuators.