Bio-Inspired Artificial Muscle-Tendon Complex of Liquid Crystal Elastomer for Bidirectional Afferent-Efferent
Jiyeon Cho1, Minhee Lee1, Taejun Park1
1Department of Mechanical Engineering, Institute of Advanced Machines and Design, Institute of Engineering Research, Seoul National University, Seoul, 08826, Republic of Korea.
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The muscle-tendon complex (MTC) in biological systems integrates contractile actuation and proprioceptive sensing, enabling coordinated feedback control of muscle activations through simultaneous afferent (sensory) and efferent (motor) signaling. To achieve similar functionality, artificial muscles, often based on polymeric materials with intricate material behaviors, require embedded proprioceptive capabilities to enable adaptive and reliable feedback control. Here, an artificial MTC-inspired liquid crystal elastomer (LCE) muscle with embedded physical intelligence is presented that supports simultaneous sensing and actuation. The proposed system utilizes embedded liquid metal (LM) channels for Joule heating and sensing of mechanical states, such as force and length, within the LCE structure. The multimaterial design combines isotropic LCE and nematic LCE, each with distinct thermomechanical properties optimized for specific functions, allowing for responsive contractile actuation and efficient proprioception. Integrated within a single, compact structure, this artificial muscle combines all sensing and actuation components, enhancing compliance and proprioceptive functionality. Furthermore, the LCE actuators are arranged in an antagonistic pair, mirroring the setup of biological muscles, to improve controllability and coordination. These MTC-inspired LCE artificial muscles demonstrate closed-loop feedback control in robotic applications, such as a robotic finger and gripper system, highlighting the potential of embedded physical intelligence in advanced robotic control systems.
