Handedness-controlled and solvent-driven actuators with twisted fibers

Abstract

Plenty of biological materials are constructed from repeated unit cells with handed configurations, wherein the hierarchical self-assembly of handed units confers optimized mechanical properties and environmental adaptability to bulk biological materials. Inspired by biological handed architectures, we propose handedness-controlled and solvent-driven actuators by programming twisted fibers, such as twisted graphene oxide fibers (TGFs), with mirrored handedness, mechanical robustness and superb flexibility. The large twists (beyond 4800 turns per meter), hair-like diameter (down to 63 μm), large tensile strain (29%) and light weight (1.49 g cm⁻³) of TGFs enable them to provide a large start-up torque of 2.7 × 10⁻⁷ N m, and to deliver a record rotor kinetic power of 89.3 W kg⁻¹ when stimulated by polar solvents such as acetone and water. By assembling handed TGF units, we achieve precise outputting of rotor kinetic energy (from 0.78 W kg⁻¹ to 12.5 W kg⁻¹), controllable harvesting of electrical energy (from 2.37 W kg⁻¹ to 11.5 W kg⁻¹), and free handling of a heavy object. The activeness, inertness and operation of all the actuating systems are well controlled by the handedness of TGF units. They are highly stable and reversible, and maintain a high energy output efficiency over multiple operation cycles. These handedness-controlled systems are also extended to hybrid twisted fibers containing nanocomposites and polymers, indicating their general practicability. Handedness-controlled actuators open an alternative avenue for fabricating energy harvesters, responsive textiles, electronic skins and soft robots.