Soft, Water-and-Glass-Based Composite Is Stronger Than Steel

The new composite is well-suited for developing artificial tendons and ligaments, soft robots, and other applications that demand material that’s flexible yet tough enough for long-term load bearing.

Researchers in Japan have developed a soft, flexible composite material that is stronger than steel by combining hydrogels with a glass fiber fabric.

The new composite is well-suited for developing artificial tendons and ligaments, soft robots, and other applications that demand material that’s flexible yet tough enough for long-term load bearing, according to the team of researchers from Hokkaido University.

The scientists combined hydrogels that contain high levels of water with glass fiber fabric to create the materials using a similar method that’s used to produce reinforced plastics, they said. The resulting material achieves both strength and flexibility, making it novel in the field of composites, said Gong Jian Ping, a professor at the university who led the research.

Tough hydrogels have shown strong potential as structural biomaterials for use in artificial body parts, soft robots, and other applications. However, historically it’s been difficult to incorporate mechanical and load-bearing properties into them to create soft, yet remarkably strong materials that suit these purposes, she said.

 

hydro gel fabric
Researchers in Japan have developed a soft, flexible composite material that is stronger than steel by combining hydrogels with a glass-fiber fabric. The material can be used for developing artificial tendons and ligaments, soft robots, and other applications that demand material that’s flexible yet tough enough for long-term load bearing. (Source: Hokkaido University)

 

The significance of her and her team’s recent work is that they’ve developed fabric hydrogel composites that are flexible and soft, but have comparable toughness to metals, Gong told Design News.

“This is a big surprise for us,” she said. “During the development of such soft composite materials, we discovered that the energy-dissipative, tough hydrogel matrix gives synergistic effect for the substantial enhancement of the toughness of fabric-hydrogel composites.”

To achieve their results, the team used polyampholytes that have opposite charges on a sample polymer backbone, Gong said. “Such polymer forms viscoelastic, self-healing, tough hydrogels through ionic association,” she said.

By using glass fabric--which is able to form ionic bonding to the polyampholyte—the team achieved strong adhesion of the polyampholyte gels and the fabric, effectively transferring the load from the rigid fabric to the soft, energy-dissipative hydrogel matrix, Gong said. The method resulted in the tough composite material and can be applied to other composites, she said.

“The resulting materials might be used as biological load-bearing structure materials that may exceed the existing materials, such as a tendon or ligament,” Gong said.

The work provides a guide toward the universal design of soft composites with “extraordinary fracture-resistance capacity,” she and the team wrote in an abstract for a paper on their work in the journal Advanced Functional Materials.

Researchers plan to continue their work by applying a similar concept to other composites, such as tough rubbers and elastomers, Gong said.

Elizabeth Montalbano is a freelance writer who has written about technology and culture for more than 15 years. She currently resides in a village on the southwest coast of Portugal.

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