Electro-humidity responsive soft actuators based on cellulose nanofibers-nanocrystals for bioinspired applications

Abstract

Multifunctional responsive actuators have garnered considerable attention for their potential applications in soft robots, wearable devices, smart displays, environmental sensing, and biomimetic systems. Herein, we present a multifunctional color-changing ionic soft actuator that integrates electrical actuation and humidity-induced color-changing functionalities, fabricated using carboxylated cellulose nanofibers, ionic liquids, polyvinyl alcohol, cellulose nanocrystals, and poly(ethylene glycol) diacrylate. The electro-humidity responsive actuator exhibited remarkable actuation performance, including a maximum tip displacement (10.2 mm), low driving voltage (as low as 1.0 V), high operational stability (95.2% reliability after 2000 actuation cycles), broad working frequency range (0.2–3.0 Hz), and exceptional tolerance to humid environments (90% relative humidity). In addition, the actuator showcased reversible and integrated color-changing capabilities. These features enabled the design of innovative devices, such as biomimetic flowers and smart color-changing windows with tunable optical properties. Consequently, this multifunctional actuator provides a promising platform for applications in soft robots, optical anti-counterfeiting systems, information storage materials, and intelligent home technologies. © Science China Press 2025.