A Liquid Metal Artificial Muscle

Abstract

Artificial muscles possess a vast potential in accelerating the development of robotics, exoskeletons, and prosthetics. Although a variety of emerging actuator technologies are reported, they suffer from several issues, such as high driving voltages, large hysteresis, and water intolerance. Here, a liquid metal artificial muscle (LMAM) is demonstrated, based on the electrochemically tunable interfacial tension of liquid metal to mimic the contraction and extension of muscles. The LMAM can work in different solutions with a wide range of pH (0–14), generating actuation strains of up to 87% at a maximum extension speed of 15 mm s−1. More importantly, the LMAM only needs a very low driving voltage of 0.5 V. The actuating components of the LMAM are completely built from liquids, which avoids mechanical fatigue and provides actuator linkages without mechanical constraints to movement. The LMAM is used for developing several proof‐of‐concept applications, including controlled displays, cargo deliveries, and reconfigurable optical reflectors. The simplicity, versatility, and efficiency of the LMAM are further demonstrated by using it to actuate the caudal fin of an untethered bionic robotic fish. The presented LMAM has the potential to extend the performance space of soft actuators for applications from engineering fields to biomedical applications.

An On‐Chip Liquid Metal Plug Generator

“…Actuating liquid metals by applying modulated voltages has been studied for applications like electrical switches and artificial muscles. [49,50] Direct application of an oxidative potential results in local oxidation of the liquid metal which is countered by the reducing effect of NaOH. We reasoned that the application of modulated voltages should tune the interfacial tension of the liquid metal resulting in localized expansion and contraction to achieve plugs of tuneable size.…”

Self-Healable and Recyclable Dual-Shape Memory Liquid Metal–Elastomer Composites

“…Notably, the IFT can be lowered to near 0 mN/m by applying voltage to oxidize the LM in an electrolyte solution [ 13 ]. This electrochemically tunable IFT can trigger the expansion and contraction of LM droplets in sodium hydroxide (NaOH) solution, a technique that has been employed to mimic the heartbeat, as well as for muscle contractions [ 14 , 15 ]. In addition, the tunable IFT can serve as the driving force for LM droplet-based soft robots, fabricated by encapsulating the LM droplets and electrolyte solutions in a closed system [ 16 , 17 ].…”

Interfacial Engineering for Highly Stable and Stretchable Electrodes Enabled by Printing/Writing Surface‐Embedded Silver and Its Selective Alloying with Liquid Metals

“…Stretchable electrodes are the basic components of future deformable electronic devices, such as strain sensors, [1][2][3][4][5] flexible displays, [6][7][8][9] stretchable antennas, [10][11][12][13][14] stretchable supercapacitors, [15][16][17][18] and soft actuators. [19][20][21][22] However, it is still a great challenge to achieve simultaneously high stability and high stretchability in these electrodes. On the one hand, the stretchabilites of the electrodes are usually achieved with sacrificing their electric conductivities.…”