Active compliant mechanisms for optimized actuation by LCE-based artificial muscles

Compliant mechanisms leverage deformation of materials for precise, lightweight solution to transfer force and motion. By incorporating smart materials, active compliant mechanisms are formed with self-embedded actuation source. Here, we propose lightweight active compliant mechanisms that mimic biological joints, which are capable of transmitting displacements and forces from the linear contraction of artificial muscles into desired magnitudes and directions using a compact structural design. The artificial muscles are braided from liquid crystal elastomer (LCE) fibers and heating threads, competent of generating large force and stroke. Meanwhile, the compliant mechanisms are designed by topology optimization to imitate the functions of biological joints. Combining the braided artificial muscles and optimized compliant mechanisms, these active compliant mechanisms effectively achieve transmission of centralized linear actuation into multiple and various output motions, which is verified by both numerical simulations and experiments. Furthermore, we demonstrate that the active compliant mechanisms can be used for potential surgical procedures such as in -body grasping, cavity dilation, drug delivery, and suturing. The demonstrated biomimetic motions of the active compliant mechanisms hold significant potential for applications in medical devices and soft robots.