Liao Jiahe, Majidi Carmel, Sitti Metin
Physical Intelligence Department, Max Planck Institute for Intelligent Systems, Heisenbergstr. 3, 70569, Stuttgart, Germany.
Robotics Institute, Mechanical Engineering, Carnegie Mellon University, 5000 Forbes Ave, Pittsburgh, PA, 15213, USA.
Adv Mater. 2024 Jan;36(1):e2300560. doi: 10.1002/adma.202300560. Epub 2023 Nov 3.
Liquid metals, with their unique combination of electrical and mechanical properties, offer great opportunities for actuation based on surface tension modulation. Thanks to the scaling laws of surface tension, which can be electrochemically controlled at low voltages, liquid metal actuators stand out from other soft actuators for their remarkable characteristics such as high contractile strain rates and higher work densities at smaller length scales. This review summarizes the principles of liquid metal actuators and discusses their performance as well as theoretical pathways toward higher performances. The objective is to provide a comparative analysis of the ongoing development of liquid metal actuators. The design principles of the liquid metal actuators are analyzed, including low-level elemental principles (kinematics and electrochemistry), mid-level structural principles (reversibility, integrity, and scalability), and high-level functionalities. A wide range of practical use cases of liquid metal actuators from robotic locomotion and object manipulation to logic and computation is reviewed. From an energy perspective, strategies are compared for coupling the liquid metal actuators with an energy source toward fully untethered robots. The review concludes by offering a roadmap of future research directions of liquid metal actuators.
液态金属因其独特的电学和力学性能组合，为基于表面张力调制的驱动提供了巨大机遇。得益于可在低电压下进行电化学控制的表面张力缩放定律，液态金属致动器在其他软致动器中脱颖而出，具有诸如高收缩应变率和在较小长度尺度下更高的功密度等显著特性。本文综述了液态金属致动器的原理，讨论了它们的性能以及实现更高性能的理论途径。目的是对液态金属致动器的当前发展进行比较分析。分析了液态金属致动器的设计原理，包括低层次的基本原理（运动学和电化学）、中层结构原理（可逆性、完整性和可扩展性）以及高层次功能。综述了液态金属致动器从机器人运动和物体操纵到逻辑与计算等广泛的实际应用案例。从能量角度，比较了将液态金属致动器与能源耦合以实现完全无束缚机器人的策略。本文通过提供液态金属致动器未来研究方向的路线图来结束综述。
