Rapid-Responsive Hydrogel Actuators with Hierarchical Structures: Strategies and Applications

Abstract

Hydrogel actuators can generate reversible shape deformation in response to external stimuli and show promising applications in many emerging fields. However, the applications of hydrogel actuators are limited by slow actuating performance. Introduction of hierarchical structures can accelerate the response rate of the hydrogel actuators and display fascinating applications. In this review, the development and current situation of hydrogel actuators are briefly introduced first, then the design strategies of hydrogel actuators with rapid response rates, including fabricating an energy storage system, constructing a microporous structure, integrating a micro/nanocomponent, and utilizing electrostatic repulsion, are summarized, followed by the promising applications of rapid-responsive hydrogel actuators. Finally, the challenges and future perspectives are highlighted.

Dual Cross-Linked Stimuli-Responsive Alginate-Based Hydrogels

“…Herein, we used calcium diffusion as a mean to prepare alginate actuators creating a gradient of dual-cross-linking with a calcium-rich phase and a calcium-poor/free phase. The described system is obtained via a simple one-step preparation without any risk of delamination, as the preparation does not involve the bilayer systems, as described in the literature. , For instance, Kirillova et al reported self-folding alginate films through a direct ink writing printing process creating a bilayer system . They also obtained self-folding films with modified hyaluronic acid where the actuating mechanism is more related to the hydrogel film preparation process than to the exploitation of the cross-linking chemistry.…”