Direct current electric field induced gradient hydrogel actuators with rapid thermo-responsive performance as soft manipulators

Polymeric hydrogels as biomimetic soft actuators have attracted great attention, but the design of rapid responsive hydrogel actuators via a facile and sustainable pathway still faces great challenges. Herein, rapid thermo-responsive hydrogel actuators with high performances were fabricated by utilizing a direct current (DC) electric field to induce a gradient distribution of renewable tunicate cellulose nanocrystals (TCNCs) in the poly(N-isopropylacrylamide) (PNIPAM) matrix. The spatial distribution of TCNCs that acted as both nanofillers and multifunctional cross-linkers in PNIPAM was adequately demonstrated by 3D Raman technology, which played a dominant role in the fast bending (4.8 degrees s(-1)) and recovery velocity (1.4 degrees s(-1)) of the corresponding hydrogel actuators. Moreover, the PNIPAM/TCNC hydrogels with excellent durability and stability could be used as potential temperature-controlled manipulators for long-term capture and transportation of targeted objects, even in harsh environments.