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Smart hydrogel actuators with excellent biocompatibility and biodegradation are extremely desired for biomedical applications. Herein, we have constructed bio-hydrogel actuators inspired by the bilayer structures of plant organs from chitosan and cellulose/carboxymethylcellulose (CMC) solution in an alkali/urea aqueous system containing epichlorohydrin (ECH) as a crosslinker, and demonstrated tight adhesion between two layers through strong electrostatic attraction and chemical crosslinking. The bilayer hydrogels with excellent mechanical properties could carry out rapid, reversible, and repeated self-rolling deformation actuated by pH-triggered swelling/deswelling, and transformed into rings, tubules, and flower-, helix-, bamboo-, and wave-like shapes by effectively designing the geometric shape and size. The significant difference in the swelling behavior between the positively charged chitosan and the negatively charged cellulose/CMC layers generated enough force to actuate the performance of the hydrogels as soft grippers, smart encapsulators, and bioinspired lenses, showing potential applications in a wide range of fields including biomedicine, biomimetic machines, etc.
Duan et al. (Wed,) studied this question.