Xiuyuan Han

Abstract Achieving adhesion between hydrogels and diverse materials in a facile and universal way is challenging. Existing methods rely on special chemical or physical properties of the hydrogel and adherends, which lead to limited applicability and complicated pretreatments. A stitch‐bonding strategy is proposed here by introducing a polymer chain with versatile functional group and triggerable crosslinking property inspired by catechol chemistry. The polymer chain can stitch the hydrogel by forming a network in topological entanglement with the preexisting hydrogel network, and directly bond to the adherend surface by versatile chemical interactions. Through this, the polymer chain solution works as a universal glue for facile adhesion of hydrogels to diverse substrates like metals, glasses, elastomers, plastics, and living tissues, without requiring any chemical design or pretreatment for the hydrogel and adherends. The adhesion energy between polyacrylamide hydrogel and diverse substrates can reach 200–400 J m −2 , and it can reach ≈900 J m −2 with a toughened polyacrylic acid polyacrylamide hydrogel. The mechanism of stitch‐bonding strategy is illustrated by studying various influence factors.

Significance Many surgeries require surgical mesh to be attached firmly at target areas to strengthen tissues, support organs, or repair wounds. Common methods of attachment include sutures, staples, and spiral tacks, but they damage tissues and prolong surgeries. Adhesion has been considered a promising alternative method to attach surgical meshes to tissues, but existing approaches of adhesion are too weak for most applications. Here, we develop composites of hydrogels and surgical meshes that can adhere to tissues firmly and stably. We demonstrate the applications of the hydrogel–mesh composites to wound closure, especially on tissues under high pressure or great tension.

Abstract The controlling of anisotropic structure in smart hydrogels is essential to fabricate hydrogel‐based soft actuators. Herein, a facile strategy to fabricate smart hydrogel with controllable anisotropic structure and the corresponding deformability is proposed. Poly( N ‐isopropylacrylamide) (PNIPAM) hydrogel is fabricated as actuator by asymmetric growth of silver (Ag) microdendrite structures in the hydrogel matrix through a phototriggered electroreduction. The existence of Ag microdendrite structures at specific area in hydrogel changes the swelling/shrinking rates of the related region, which driving the deformation behavior of the hydrogel. By adjusting the electroreduction parameters and the patterns on the reducing electrode, distribution of Ag microstructures both along the vertical and lateral direction in hydrogel matrix can be precisely controlled, which further enables designed deformations of the hydrogel nanocomposites. As a result, various soft actuators such as bending beam, gripper, and flower‐shaped actuator are designed, and the temperature triggered actions of these actuators, such as curling and gripping are realized.