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A polymer-based nanofiber composite actuator designed for contractile actuation was fabricated by electrospinning,
stimulated by electrolysis, and characterized by electrochemical and mechanical testing to address performance
limitations and understand the activation processing effects on actuation performance. Currently, Electroactive polymers
(EAPs) have provided uses in sensory and actuation technology, but have either low force output or expand rather than
contract, falling short in capturing the natural kinetics and mechanics of muscle needed to provide breakthroughs in the
bio-medical and robotic fields. In this study, activated Polyacrylonitrile (PAN) fibers have demonstrated biomimetic
functionalities similar to the sarcomere contraction responsible for muscle function. Activated PAN has also been shown
to contract and expand by electrolysis when in close vicinity to the anode and cathode, respectively. PAN nanofibers
(~500 nm) especially show faster response to changes in environmental pH and improved mechanical properties
compared to larger diameter fibers. Tensile testing was conducted to examine changes in mechanical properties between
annealing and hydrolysis processing. Voltage driven transient effects of localized pH were examined to address pHdefined
actuation thresholds of PAN fibers. Electrochemical contraction rates of the PAN/Graphite composite actuator
demonstrated up to 25%/min. Strains of 58.8%, ultimate stresses up to 77.1 MPa, and moduli of 0.21 MPa were achieved
with pure PAN nanofiber mats, surpassing mechanical properties of natural muscles. Further improvements, however, to
contraction rates and Young’s moduli were found essential to capture the function and performance of skeletal muscles
appropriately.
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