The Role of Rigidity in Soft Robotic Fabrics

Fabrics are breathable, conformable, and compactible interlaced fiber structures, which makes them the perfect material for wearables, among many other everyday applications. Given their ubiquity, the possibility of "roboticizing" fabrics could lead to smart adaptive clothing, self-deploying shelters, and lightweight, stowable, shape-changing machines. Ideally, a robotic fabric's actuation, sensing, and structural support should be provided by fiber-based components, designed to integrate seamlessly with the fabric's soft and conformable nature. Variable-stiffness mechanisms are often used for the structural elements, functioning as "bones" that can be turned on and off as needed. However, many available fiber-based variable-stiffness mechanisms are passively rigid, only allowing the fabric to become soft when powered, and others require bulky external air or power supplies, making them untenable for untethered robots. In this talk, I will present a new electrically-driven variable-stiffness fiber that can provide a rigid load-bearing structure when powered, but remains flexible otherwise. The active variable-stiffness fibers are stable enough for a robotic fabric to lift and locomote with its own battery pack and onboard electronics, enabling a fully untethered locomoting robotic fabric. I will also present new fabric capacitive sensors that exhibit high strains, cyclic stability, and high water-vapor transmission rates, the latter of which allows for sweat evaporation, an important parameter of comfort in wearable applications. Finally, I will speculate on the combination of the fabric sensors with actuated and variable-stiffness fabrics for human motion monitoring and haptic feedback.