Multimaterial Fibers as Bioinspired Actuators

Multimaterial fibers have empowered photonics, minimally-invasive surgery, electronic textiles, and more recently neural interfaces. The compatibility of fiber-drawing process with a diversity of materials ranging from soft polymers to highly-conductive metals or custom composites as well as the high-throughput fabrication, invites their further exploration in biomedical and bioengineering fields. The filamentous nature of fibers has previously led us to draw inspiration from biological actuation seen in climbing plants and fabricate light-weight and miniature artificial muscles that could be actuated by modest temperature gradients. Although a promising initial demonstration, the reliance of these fibers on externally applied heat made them challenging to implement in engineering systems. We now expand on these initial findings, and demonstrate fiber-based artificial muscles actuated electrically with speed and responsiveness rivaling their biological counterparts. We additionally, demonstrate that fiber mechanics responsible for actuation in fiber-based muscles, can be leveraged to create soft three-dimensional robots with microscale features. When embedded with magnetic composites, these soft robots can be programmed as crawlers or walkers able to propel themselves under unidirectional, weak, slow-varying magnetic fields produced by standard electromagnets, thus addressing one of the key challenges in magnetically-actuated locomotors that typically rely on rotating fields. Given the versatility of fiber fabrication, these soft robots and actuators can then be equipped with additional functional features including drug or light delivery needed desirable in biomedical research or minimally-invasive surgery.