Hydrogel Adhesion: A Supramolecular Synergy of Chemistry, Topology, and Mechanics

Abstract

Adhering hydrogels to various materials is fundamental to a large array of established and emerging applications. Last few years have seen transformative advances in achieving strong hydrogel adhesion. Hydrogel adhesion is a supramolecular phenomenon. Two adherends connect through covalent bonds, noncovalent complexes, polymer chains, polymer networks, or nanoparticles.Separating the adherends dissipates energy through cascading events across length scales, including bond cleavage, chain retraction, and bulk hysteresis. A unifying principle has emerged: strong hydrogel adhesion requires the synergy of chemistry of bonds, topology of connection, and mechanics of dissipation. This synergy characterizes hydrogel adhesion to various materials (another hydrogel, tissue, elastomer, plastic, metal, glass, ceramic), in various operations (cast, coat, print, attach, pierce, glue). Strong adhesion can be made permanent, reversible, degradable, or ondemand detachable. The development of hydrogel adhesion and its applications adheres disciplines, discovers interlinks, and forges cohesion. Discussed throughout the review are immediate opportunities for fundamental studies and practical applications.

Recent Progress in the Electrolytes of Aqueous Zinc‐Ion Batteries

“…For instance, the liquid‐electrolyte‐based devices would suffer from the possible leakage of harmful electrolytes and undesired dislocation under strain . To avoid these issues, some hydrophilic polymers or inorganic components can be introduced into the Zn‐containing salt solutions to achieve gel electrolytes . Compared with liquid electrolytes, the gel electrolytes exhibit relatively lower ionic conductivity, inferior electrode/electrolyte interfaces, and high overpotential.…”

“…[40] To avoid these issues, some hydrophilicp olymers or inorganic components can be introduced into the Zncontaining salt solutions to achieve gel electrolytes. [41] Compared with liquid electrolytes, the gel electrolytes exhibit relatively lower ionic conductivity,i nferiore lectrode/electrolyte interfaces,a nd high overpotential. However,g el electrolytes possess high physical flexibility,d esirable electrochemical properties and excellent mechanical integrity,a nd coulds erve as both electrolyte and separator simultaneously.F urthermore, in some cases, gel electrolytes can also inhibitt he Zn dendrite growth and enhancee lectrochemical stability.…”

Fabrication and Mechanical Properties of Engineered Protein‐Based Adhesives and Fibers

“…Interestingly, the aggregation of noncovalent bonds can strongly increase the interaction among polymer chains, resulting in the formation of the polymer complex. Thus, the adhesion is still considerable even without the formation of covalent bonds . In most cases, catechol groups play a critical role in tuning the adhesion performance of protein‐based adhesives.…”

Design of Active Interfaces Using Responsive Molecular Components

“…In many applications, not simply the strongest possible adhesion between two materials, but rather the control over the adhering properties is of prime interest, so that components in complex devices can be easily recycled simply by deactivating the adhesive. Materials that are capable of self‐healing (such as supramolecular hydrogels) are one interesting approach toward responsive adhesion, since the self‐healing nature allows for repeatable gluing events after breakage . Interestingly, the majority of responsive glues is based on host–guest interactions or dynamic covalent bonds.…”