High-Performance Multiresponsive Paper Actuators

TLDR

Soft actuators are increasingly sought for soft robotics, artificial muscles, and biomimetic devices, yet achieving low‑voltage, powerful, and programmable shape‑changing actuation remains difficult. We propose programmable bilayer actuators that bend when heated, driven by the hygroscopic contraction of copy paper and the thermal expansion of a polypropylene film, and can also be actuated by humidity or light. The devices operate at ≤8 V, consume ≤0.14 W cm⁻², and require ≤35 °C temperature change, achieving reversible bending with curvature up to 1.07 cm⁻¹ and 360° angles. These actuators were demonstrated as a soft gripper robot and a lightweight paper wing for aerial robotics.

Abstract

There is an increasing demand for soft actuators because of their importance in soft robotics, artificial muscles, biomimetic devices, and beyond. However, the development of soft actuators capable of low-voltage operation, powerful actuation, and programmable shape-changing is still challenging. In this work, we propose programmable bilayer actuators that operate based on the large hygroscopic contraction of the copy paper and simultaneously large thermal expansion of the polypropylene film upon increasing the temperature. The electrothermally activated bending actuators can function with low voltages (≤ 8 V), low input electric power per area (P ≤ 0.14 W cm-2), and low temperature changes (≤ 35 °C). They exhibit reversible shape-changing behavior with curvature radii up to 1.07 cm-1 and bending angle of 360°, accompanied by powerful actuation. Besides the electrical activation, they can be powered by humidity or light irradiation. We finally demonstrate the use of our paper actuators as a soft gripper robot and a lightweight paper wing for aerial robotics.