Bioinspired smart moisture actuators basedon nanoscale cellulose materials and porous, hydrophilic EVOH nanofibrousmembranes

Abstract: Biomimetic actuators with rapid responsespeed, high sensitivity, and selectivity to external stimulus have foundpotential applications in smart switches, artificial muscles, and soft robots.The nanoscale structures of actuators enhance the exposed area to stimulus aswell as enable versatile control of the actuation behaviors. Freestanding,flexible, and porous water-driven actuators with poly(vinylalcohol-co-ethylene) (EVOH) nanofibers as the substrate and super hydrophilicnanoscale cellulose materials (cellulose nanofibers, cellulose nanocrystals,bacterial cellulose) as the active substance via uniform mixing or surfacedepositing were fabricated. The effects of the EVOH nanofiber substrate, thestructures and concentrations of nanoscale cellulose materials, as well as thedifferent environmental stimuli like humidity and temperature on theperformance of actuators were studied. The water-driven actuation mechanism wasproposed from the macroscopic and molecular aspects and the analysis of Gibbsfree energy and mechanical energy. The actuator could bend to an angle of 180°and recovered less than 1 s for more than 100 circles without compromisingproperties when the environmental moisture changed. Furthermore, themultidimensional deformation behaviors of the water-stimulated actuators couldalso be well tuned by varying the orientations of the nanoscale materials.Additionally, the applications of the prepared actuator were demonstrated.

Zhu Qing, et al.Bioinspired smart moisture actuators based on nanoscale cellulose materials andporous, hydrophilic EVOH nanofibrous membranes. ACS applied materials & interfaces, 2018, 11, 1440-1448.