Sustainable mechanochemical growth of double-network hydrogels supported by vascular-like perfusion.

Double-network (DN) gels are unique mechanochemical materials owing to their structures that can be dynamically remodelled during use. The mechanical energy applied to DN gels is efficiently transferred to the chemical bonds of the brittle network, generating mechanoradicals that initiate the polymerisation of pre-loaded monomers, thereby remodelling the materials. To attain continuous remodelling or growth in response to repetitive mechanical stimuli, a sustainable supply of chemical reagents to such dynamic materials is essential. In this study, inspired by the vascular perfusion transporting nutrients to cells, we constructed a circulatory system for a continuous supply of chemicals to channel-containing DN hydrogels (c-DN gels). The perfusion of monomer solutions through the channel and permeability of the c-DN gels not only replenishes the monomers consumed by the polymerisation but also replenishes the water loss caused by the surface evaporation of hydrogel, thereby freeing the mechanochemical process of DN gels from the constraints of the underwater environment. The facile chemical supply enabled us to modulate the mechanical enhancement of the c-DN gel and attain muscle-like strengthening under repeated mechanical training in deoxygenated air. We also studied the kinetics of polymer growth and strengthening and deciphered unique features of mechanochemical reaction in DN gels including the extremely long-living radicals and delayed mechanical strengthening.

Reversible Dendritic-Crystal-Reinforced Polymer Gel for Bioinspired Adaptable Adhesive.

High-strength and reversible adhesion technology, which is a universal phenomenon in nature but remains challenging for artificial synthesis, is essential for the development of modern science. Existing adhesive designs without interface versatility hinder their application to arbitrary surfaces. Bioinspired by creeper suckers, a crystal-fiber reinforced polymer gel adhesive with ultrastrong adhesion strength and universal interface adaptability is creatively prepared via introducing a room-temperature crystallizable solvent into the polymer network. The gel adhesive formed by hydrogen bonding interaction between crystal fibers and polymer network can successfully realize over 9.82 MPa reversible adhesion strength for rough interface and 406.87 J m-2 peeling toughness for skin tissue. In situ anchoring is achieved for adapting to different geometrical surfaces. The adhesion performance can be significantly improved with the further increase of the interfacial roughness and hydrophilicity, whose dissipation mechanism is simulated by finite element analysis. The melting-crystallization equilibrium of the crystal fibers is proved by synchrotron radiation scattering. Accordingly, reversible phase-transition triggered by light and heat can realize the controlled adhere-detach recycle. Later adjustments to the monomers or crystals are expected to broaden its applications to various fields such as bioelectronics, electronic processing, and machine handling.