Thin-film dynamic friction modulator interfaced with PVC-gel charge accumulator for variable clutching of robotic systems

Realizing programmable mechanical compliance is essential for ensuring safety and adaptability in robotic systems. While active frictional interfaces utilizing electrostatic forces offer a desirable lightweight form factor, they generally suffer from high driving voltages. Furthermore, sliding-induced stick–slip instabilities prevent precise friction modulation, typically restricting their functional range to simple binary (on/off) modes. Here, a thin-film dynamic friction modulator is presented, enabling stick–slip-free, variable clutching via tunable electromechanical dynamics of a polyvinyl chloride (PVC)-gel charge accumulator. Unlike conventional dielectrics, the PVC-gel utilizes interfacial charge accumulation to generate exceptionally strong electrostatic forces, resulting in high shear stress capacity (~ 29 N/cm² at 100 V). Crucially, optimizing plasticizer in the PVC-gel results in suppressing stick–slip by concurrently minimizing the static-kinetic friction disparity and inducing velocity-strengthening friction response contributing to sliding continuity. This synergy ensures stick–slip-free sliding and precise kinetic friction control even under high shear stress (22.5 N/cm²). The versatility of this mechanism is validated across robotic control systems, including programmable impact damping, variable clutch, and wearable haptic device. By transcending conventional binary friction control, this thin-film friction modulator establishes a versatile platform for continuous dynamic control.