AsianScientist (Feb. 7, 2019) – A research group in Japan has found a method to develop stronger, longer-lasting materials using a strategy inspired by the process responsible for muscle growth. They published their findings in the journal Science.
When bodybuilders work out in the gym, the strain causes muscle fibers to break down, releasing factors that promote the formation of new, stronger fibers. For this to happen, the muscles must be supplied with amino acids, the building blocks of proteins.
Mimicking this process in natural muscle, researchers led by Professor Gong Jian Ping of Hokkaido University, Japan, developed what they call double-network hydrogels made from 85 percent water and two types of polymer networks—one rigid and brittle, the other soft and stretchable.
The team placed a double-network hydrogel inside a solution containing molecules, called monomers, which can be joined to form larger compounds called polymers. This solution emulates the role of circulating blood carrying amino acids to skeletal muscles.
When the researchers stretched the hydrogel, the tensile force caused some of its rigid and brittle polymer chains to break. This led to the generation of a chemical species called mechanoradicals at the ends of the broken polymer chains. These mechanoradicals can trigger the joining up of the monomers absorbed into the hydrogel from the surrounding solution, creating a polymer network that strengthens the material.
With successive stretching, more breaking down and building up occurs, similar to what happens with skeletal muscles undergo strength training. Through this process, the hydrogel’s strength and stiffness improved by 1.5 and 23 times respectively, and the weight of the polymers increased by 86 percent.
The team was further able to tailor the material’s response to mechanical force by using a specific monomer that altered the gel’s reaction to heat. The gel’s surface became more water-resistant when heated.
The researchers say their work could help with the development of self-growing gel materials for applications such as flexible exosuits for patients with skeletal injuries. These suits would potentially become stronger and more functional the more they are used.
“Since many types of double-network gels have similar mechanical features, this process could be applied to a wide range of gels, expanding the range of potential applications,” said Gong.
The article can be found at: Matsuda et al. (2019) Mechanoresponsive Self-growing Hydrogels Inspired by Muscle Training.
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Source: Hokkaido University.
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