Biomimetic sea-cucumber: stiffness fast-reversible, turbidity switchable, shape-memorable and self-healing hydrogel

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Yang, Ruijia
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Natural biological models that possess attractive features clue us on the designing of smart devices. Echinoderms such as sea cucumbers lead the way to design stimuli-responsive stiffness-change materials; self-recovery abilities of skin inspire the generation of self-healing materials; and the touch-sensitive behaviors of mimosas spark the concept of shape-memory. Hydrogels are wildly used as biomaterials, and those with multifunctionalities have attracted widespread attention due to their potential in the biomedical area. However, the successful construction of multifunctional hydrogels remains a challenge because the desired functions are always hard to be tailored together. Therefore, the means to successfully build these hydrogels are of great demand. This study reports a stimuli-responsive hydrogel based on the double network (DN) system, and it shows biomimetic functions such as tremendous reversible stiffness changes, outstanding shape-memory and self-healing abilities. The hydrogel consists of carboxymethyl-chitosan (CM) and acrylamide (AM) where the AM network is set to be the primary network to provide a soft matrix, while the CM network is set to be the second network that can be reversibly generated/eliminated through cyclic acid-base treatments. Due to this mechanism and the inherent rigid property of the CM network, this hydrogel exhibits reversible stiffness changes (an increase by a factor of 100 of compressive modulus), excellent self-healing capabilities (91% of self-healing efficiency) and outstanding shape-memory performances (100% of shape-fixing efficiency and 97% of shape-recovery ratio). The DN hydrogel can be applied as motion sensors, “on-demand” switches and “LEGO-like” 3D printing ink. In summary, this study presents a new strategy to fabricate multifunctional hydrogels that can have great potential in the biomedical area.
Carboxymethyl Chitosan, Double-network hydrogel, multifunctional