Active Variable Stiffness Fibers for Multifunctional Robotic Fabrics

In this letter, we introduce active variable stiffness fibers that are made from shape memory alloy and thermally responsive polymers. This combines the actuation of shape memory alloy with the variable stiffness of a thermoplastic using electric current as the stimulus. By combining both actuation and variable stiffness functions, the multifunctional fibers can move to a new position then hold that position without requiring additional power. We explore the possibility of tuning the fibers to meet varying structural and performance demands by selecting different thermoplastics with different glass transition temperatures. Finally, we integrate the active variable stiffness fibers into a fabric to demonstrate multifunctional robotic fabrics that can control the motion of soft, compliant bodies from their surface.