Robust Hydrogel Adhesion by Harnessing Bioinspired Interfacial Mineralization

Abstract

Hydrogels have gained intensive interest in biomedical and flexible electronics, and adhesion of hydrogels to substrates or devices is indispensable in these application scenarios. Although numerous hydrogel adhesion strategies have been developed, it is still challenging to achieve a hydrogel with robust adhesion interface through a universal yet simple method. Here, a strategy for establishing strong interfacial adhesion between various hydrogels and a wide variety of substrates (i.e., soft hydrogels and rigid solids, including glass, aluminum, PET, nylon and PDMS) even under wet conditions, is reported. This strong interfacial adhesion is realized by constructing a bioinspired mineralized transition layer through ion diffusion and subsequent mineral deposition. This strategy is not only generally applicable to a broad range of substrates and ionic pairs, but also compatible with various fabrication approaches without compromising their interfacial robustnesses. This strategy is further demonstrated in the application of single‐electrode triboelectric nanogenerators (TENG), where a robust interface between the hydrogel and elastomer layers is enabled to ensure a reliable signal generation and output.

Bio‐inspired adhesive hydrogel for biomedicine—principles and design strategies

“…59,210 Zhang et al devised a robust and universal strategy to build stable adhesions between hydrogels and various substrates, inspired by biomineralization at the cartilage-bone interface (Figure 9B). 59 Cation and anion pairs that can form solid minerals (e.g., calcium ions and phosphates) were introduced in the hydrogel and matrix, respectively. When the hydrogel came into F I G U R E 8 Bio-inspired artificial hydrogels with molecule-network interactions.…”

“…For example, in some strategies inspired by biomineralization, inorganic particles generated at the interface bind to the networks on both sides, in a way that is similar with topohesion. 59,211 Another example is that the adhesion on a surface provided by some coacervate systems still depend on sticky groups, coagulation, etc. 134,209 Besides, some bioinspired adhesions require systematic exploration.…”

“…[207][208][209] Besides, biomineralization also inspires studies on the adhesion of hybrid hydrogels. 59,210 Zhang et al devised a robust and universal strategy to build stable adhesions between hydrogels and various substrates, inspired by biomineralization at the cartilage-bone interface (Figure 9B). 59 Cation and anion pairs that can form solid minerals (e.g., calcium ions and phosphates) were introduced in the hydrogel and matrix, respectively.…”

“…These processes involve molecular chains and the interactions with the adhered network. 56,57,59,131,132 Phase behaviors related to adhesion include phase separation, mainly coacervation (Figure 5J), and phase transitions, including solidification and mineralization (Figure 5K,L). 55,57,[59][60][61][133][134][135] Similar to the previous chapter, various biological molecular-related adhesion principles and corresponding artificial adhesion strategies of hydrogels are discussed.…”

“…This can be originated from, for example, sticky components of mussel adhesives, [47][48][49][50] entanglement of macromolecules in mucus, 51,52 the complementary pairing of receptor-ligand, 53,54 and phase behaviors such as coacervation, solidification, and biomineralization of sandcastle worms. 21,[55][56][57][58][59][60][61] Intriguingly, these natural strategies have recently been well implemented in the design of hydrogels to achieve bioadhesion. The resultant hydrogels have found widespread applications in biomedicine, including patches with interlocking microneedles, [62][63][64][65] suction cups, [66][67][68][69] and hydrogels grafted with sticky groups, [70][71][72][73] etc.…”