New self-growing material able to strengthen in response to force

Inspired by natural muscle growth process, researchers have created a self-growing material that strengths itself in response to force, paving way for stronger, longer-lasting materials.

Researchers from Hokkaido University have developed a strategy to fabricate materials that become stronger in response to mechanical stress, similar to skeletal muscle growth.

The researchers took inspiration by the process that makes human skeletal muscles become stronger. For instance, after strength training at the gym, muscle fibers break down hence encouraging the formation of new, stronger fibers. For this, the muscles must be supplied with amino acids, that join together and form muscle fibers, explained Science Daily.

The team developed the strategy employing ‘double-network hydrogels’ that imitates the building process of skeletal muscles. The hydrogels are a soft, yet tough material formed of about 85 weight percent water and two types of polymer networks – one rigid and brittle, and other soft and stretchable.

The hydrogel was placed inside a solution consisting of molecules called monomers, which can be joined to form longer compounds called polymers. The solution mimics the role of circulating blood carrying amino acid to skeletal muscles.

Applying force (stretching) to the hydrogel caused some of its rigid and brittle polymer chains to break, hence generation of chemical species ‘mechanoradicals’ at the ends of the broken chains. The species can trigger the joining up of the monomer absorbed into the hydrogel from the surrounding solution into a polymer network, strengthening the material.

With more stretching, more breaking down and building up took place. Through this the hydrogel’s strength and stiffness improved 1.5 and 23 times respectively and the polymers’ weight increased by 80%.

Researchers believe that their work can help develop self-growing gel materials for applications like flexible exosuits for patients with skeletal injuries, which can become stronger and more functional the more they are used.