Spontaneously Regenerative Tough Hydrogels

Abstract

Sponges, Neofibularia nolitangere, can regenerate spontaneously after being broken down into small pieces, and the regenerated structure maintains the original appearance and function. Synthetic materials with such capabilities are highly desired but hardly achieved. Presented here is a spongeinspired self-regenerative powder from a double-network (DN) tough hydrogel. Hydrogels are regenerated from their powder form, by addition of water, with preservation of the original appearance and mechanical properties. The powderhydrogel-powder cycle can be repeated multiple times with little loss in mechanical properties, analogous to the regeneration of sponges. These DN hydrogels can be conveniently stored and easily shaped upon regeneration. This work may have implications in the development of regenerative materials for coatings and adhesives.In nature many animals can heal and regenerate after severe injury or even loss of significant bodily portions. [1][2][3] Sponges, Neofibularia nolitangere, the simplest form of multicellular organisms, has a fascinating regenerative capacity. [1,2] In sea water, small fragments of cell aggregates that are dissociated from Neofibularia nolitangere can fuse into functional mass and reassemble into its original form after being prompted. The regeneration of Neofibularia nolitangere is a consequence of a complex collaboration of multiple cell types through metabolism. [1,2] The capacity for reconstruction after injury is rare, but highly desired in synthetic materials, which typically deteriorate and even fail after repetitive exposure to mechanical strain.There are some reports addressing self-healing materials that can partially, or even completely restore their mechanical properties. [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] Existing self-healing strategies based on either dynamic covalent or physical bonds have certain limitations. [5, 10-12, 15, 22-26] For instance, self-healing strategies based on supramolecular interactions are inefficient for healing a large area with severe damage, [12,15,16,21,27,28] for self-healing of physical bonds when the damage is no longer fresh because the effect of healing becomes weak and even disappears, [25,26,[29][30][31] and for repair of dynamic covalent bonds because external conditions need be applied. [22,32,33] Moreover, most healing strategies cannot be applied in both wet and dry conditions. [20,34,35] Although the development progress of self-healing materials has been impressive, those capable of regaining their properties rapidly from aged and severe damage are scarce. [36] Healing to restore the original form and full function, like Neofibularia nolitangere, even when reduced into countless pieces, is still desired for most synthetic materials.Herein we report a sponge-inspired strategy to develop self-regenerative materials. Based on double-network (DN) tough hydrogels, we fabricate hydrogel powders that can regenerate to restore the original form and appearance of the hydrogel, and almost restore...

Poly(vinyl alcohol) Hydrogels with Broad‐Range Tunable Mechanical Properties via the Hofmeister Effect

“…Toughness and modulus exhibited similar trends, which increased from 3.1 to 153.41 MJ m −3 and from 24 to 2500 kPa, respectively (Figure 2d,e,f). Note that the hydrogel soaked with saturated Na 2 SO 4 showed higher ultimate stress and strain that surpassed the values reported in previous works studying tough hydrogels (Figure 2g) by 10 to 10 3 fold, [ 41–43 ] and the corresponding toughness was larger than the water‐free polymers like PDMS, synthetic rubber and natural spider silk (Figure 2g). Furthermore, via changing the ions or concentrations, the modulus of PVA hydrogels can be easily tuned within a broad range, from near 24 to 2500 kPa, which covered all the moduli of soft tissues in the human body [ 38,44 ] as shown in Figure 2h With such a large range of moduli and biocompatibility, the PVA hydrogels can offer a very promising material platform for stem cells to differentiate into various functional cells, ranging from extremely soft brain cells to very rigid cartilage cells.…”

Particle packing into loose networks for tough and sticky composite gels

“…However, general hydrogels have low mechanical strength due to their high swelling property and non-uniform structure, which is an obstacle to their wider application and development. In order to develop a gel with high strength and toughness that overcomes this drawback, research and development has been conducted for devising effective hydrogel molecular designs [6][7][8][9][10][11] . Typical examples include the development of a slide-ring gel 8 , a tetra-poly (ethylene glycol) (PEG) gel 9 , a double network (DN) gel 10 , and a nanocomposite gel 11 .…”

A Regenerable Hydrogel Electrolyte for Flexible Supercapacitors

“…29 mS cm −1 ) ( Liu et al, 2019b ), cross-linked dopamine-grafted alginate/KCl hydrogel electrolyte for self-healable and cold-resistant SCs ( Tao et al., 2017 ), and a dynamic PVA-based network cross-linked by diol-borate ester bonding showing great capacitive restoration after breaking/healing cycles ( Wang et al., 2016 ). What's more, most of them can self-heal when slightly damaged, as for serious damage and even fragmentation, regenerability that has much better self-healing ability is required (the difference between self-healing and regeneration process is shown in Figure S1 ) ( Qu et al., 2019 ). The current research comprises striking omissions in the regenerability and structural sustainability of hydrogel electrolytes for solid-state SCs regenerated at the device level, which poses a huge challenge for the low-cost fabrication of highly reliable solid-state/flexible SCs toward enhanced practicability.…”