Recent IDTechEx Report Shows Hydrogels Get Magical

In December 2021, Cambridge University UK researchers announced this a jelly-like material that can withstand the equivalent of an elephant standing on it without breaking and then recovering its normal shape. The soft-yet-strong self-healing material acts like an ultra-hard, shatterproof glass when compressed, despite its 80% water content.

They believe it can be optimised for biomedical use for soft robotics, bioelectronics, and cartilage replacement. They also envisage a pressure sensor for real-time human motion monitoring, including standing, walking, and jumping. Barrel-shaped molecules called cucurbiturils led to the breakthrough.

The IDTechEx report states that antifouling coatings seek everything from ships to food aquaculture and human implants. In 2021 work was reported on the fabrication of bio-based amphiphilic hydrogel coating with excellent antifouling and mechanical properties using a biocidal hydrogel-based approach.

All gels will creep back after damage, but special hydrogels get optimised for human wound healing, tissue engineering, and drug delivery. Ultrasound-triggered drug delivery has been shown to improve chemotherapy when ionically cross-linked self-healing hydrogel is employed. In wound healing and tissue engineering, research eliminates problem aspects such as adhesion, and it adds useful features such as being antibacterial.

Some hydrogels are injectable for controlled release of encapsulated therapeutics (cell therapy and drug delivery) – delivered as a liquid and gelated in situ to accommodate irregular defects of the desired position.

Certain hydrogels heal chemical as well as mechanical damage incurred. For example, polyvinyl alcohol is a biocompatible and non-toxic synthetic polymer with a crystalline nature used to synthesise hydrogel via a freezing/thawing method. This can exhibit a highly self-healing ability without any peripheral stimulus at room temperature.

Metallo-polymeric hydrogels prove useful for recoverable properties, self-healing, and other functions. The subject of self-healing polymeric hydrogels is progressing rapidly. Needs in healthcare primarily drive it. After all, they are exceptionally biocompatible: no surprise because they greatly resemble biological systems. Both physical diffusion of molecules and chemical recombination of the cleaved bonds assist the process of self-healing in hydrogels.

Extrinsic self-healing employs artefacts such as embedded microcapsules that release reagents when the material is cracked. For extrinsic self-healing capability in polymers, one option is to copy the surface structure of animals.

Avascular (piped liquid) network is present throughout the part, so fast-acting polymerisation agents can be pushed through this system when a crack occurs. Advantages are easy to replenish, linked with self-healing hydrogel, and repeated repairs. Not quite a sea slug was repeatedly regrowing its head or even a lizard growing a new tail but valuable nonetheless. Disadvantages include being slower to do the healing requiring an external pumping network.

As we learn from nature, we make stretchable and creeping polymers such as hydrogels that inherently ‘intrinsically’ creep into damage, but artefacts like microcapsules are often needed.

As the IDTechEx report, Advanced Wound Care Technologies 2020-2030 explains, tissue engineering seeks to develop tissue and organ substitutes for maintaining, restoring, or augmenting functions of their injured or diseased counterparts in vivo. Increasing demand for biomaterials for regeneration or replacement of damaged tissue drives the development of new tissue engineering structures.

Demand for engineered tissues is rapidly growing due to the limited availability of donor tissues and organs for transplantation. Tailored multifunctional hydrogels can be excellent cell delivery vehicles for therapeutic healing and tissue regeneration because of their high water content and responsiveness to various environmental stimuli such as temperature, pH, and enzymes.

The properties of these hydrogels derive from their molecular structure. Namely, their highly swollen, hydrophilic 3D cross-linked polymer network may be either chemically or physically cross-linked to form a material that mimics advantageous properties of the highly hydrated extracellular matrix (ECM) and facilitates nutrient and oxygen transport due to its porous structure. Hydrogels have a long history as tools for tissue regeneration and 3D cell culture. They may be engineered to mimic the desired aspects of the native local ECM depending on their intended usage.

Supramolecular hydrogels are now emerging as a promising tool for tissue regeneration. They can be made biocompatible and recapitulate the viscoelastic nature of the ECM better than their elastic, covalently cross-linked counterparts due to the presence of dynamic linkages. These linkages’ resulting viscoelastic and dynamic behaviour is responsible for other advantages such as self-healing and injectability.

Supramolecular hydrogels can self-heal after damage either spontaneously or in the presence of a physiological stimulus. This characteristic extends the lifetime of materials and makes them ideal candidates for applications involving repeated mechanical stress or injection.

Ideally, hydrogels for tissue engineering should enable cell infiltration and encapsulate and deliver cells and biologics and be able to autonomously, rapidly, and repeatedly heal in situ at physiological conditions. Adhesives that are naturally self-healing are an important part of most tissue engineering procedures. Commonly used tissue adhesives include hydrogels because of exceptional adhesion and non-toxicity.

Routes to self-healing hydrogels are vast in number. Some based on natural polymers include supramolecular interactions or reversible covalent bonds. That includes chitosans, alginates, and celluloses. Alternatives are synthesised inorganic, organic, or composite materials. It can be complicated but worthwhile. For instance, amphiphilic diblock copolypeptide hydrogels DCHs are synthetic materials exhibiting tunable composition, structure, and properties.

The addition of polyelectrolyte provides self-healing, shear-thinning, and biocompatibility that have been widely applied as biomaterials. Self-healing hydrogel based on metal-ligand assembly has been successfully used in bone regeneration. We could talk about the new self-healing hydrogel electrolyte in supercapacitors but let us settle by saying that hydrogels are truly becoming the gymnasts of chemistry.