Fiber-Format Flexible Linear Electrostatic Motors.

Linear motion is fundamental to robotics, yet existing solutions are either rigid electromagnetic motors or contractile artificial muscles with limited stroke and trade-offs in force versus displacement. We report a sliding motor in a thin fiber format: a flexible, electrostatic linear actuator with a stroke limited only by fiber length. Comprising two coaxial fibers with helically wound electrodes, this "FiberMotor" generates bidirectional, fast, stepping motion with stroke-independent force and inherent back-drivability, a key feature for safe and transparent human-robot interaction. By eliminating permanent magnets and Joule heating, it offers a compact alternative to traditional motors. Modular bundling allows scaling to higher forces. Supported by an analytical model, this silent, lightweight technology can enable large-scale integration into textiles, providing a promising building block toward future soft exosuits and wearable assistive devices.