Scalable, Addressable, Artificial Muscle Bundles

Skeletal muscle continues to serve as an inspiration for the design of scalable, energy efficient, soft robotic actuators with distributed sensorimotor capabilities. However, our ability to produce soft actuators that mimic skeletal muscle remains limited. Liquid crystal elastomers (LCEs) are one promising class of materials whose high power density and large, contractile actuation strain approach the performance of biological muscle. Despite these advantages, the common actuation stimuli needed to drive LCEs are hindered by severe limitations. In addition to low actuation bandwidth, thermally-driven or thermotropic LCEs are energy inefficient, while photo-driven or phototropic varieties are limited to thin form factors that typically bend rather than contract. Here, we present LCE composite fibers that linearly contract while enabling in-line delivery of target stimuli. We demonstrate that bundling individual artificial muscle fibers introduces new capabilities such as scalability, amplified force output, and addressable actuation. Moreover, we show that our overall design strategy for artificial muscles alleviates stimuli transport-related challenges of existing LCE soft actuators by coupling the actuation stimuli with the active material. Our artificial muscle fiber bundles, which integrate scalability and addressability in a manner not yet seen in LCEs and other soft robotic actuators, provide a step towards designing material systems that truly mimic the performance and controllability of skeletal muscle. They serve as a platform for future multifunctional, artificial muscle designs that tightly integrate distributed actuation, sensing, control, and energy capabilities.