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New material for soft robots and PPE can heal itself ‘immediately’

Professional Engineering

Actuators made with the biosynthetic polymer repeatedly lift a weight. The material can self-heal damage from repeated use (Credit: Demirel Lab, Penn State)
Actuators made with the biosynthetic polymer repeatedly lift a weight. The material can self-heal damage from repeated use (Credit: Demirel Lab, Penn State)

A new ‘biosynthetic’ polymer can quickly heal itself using just water and heat, leading the way towards soft robot actuators and protective equipment that repair damage automatically.

The material, developed at Penn State University in Pennsylvania, mimics DNA found in squid ring teeth, which grip onto prey. It could be useful in many applications where small holes or cracks pose danger to the operation or safety of a device.

Current self-healing materials have shortcomings that limit their practical application, such as low healing strength and long healing times, the researchers said.

To create an improved material, the team produced high-strength synthetic proteins which self-heal both tiny and visible damage. The researchers created the self-healing polymer by using a series of DNA tandem repeats, made up of amino acids produced by gene duplication. The researchers manufactured the polymer in standard bacterial bioreactors.

“We were able to reduce a typical 24-hour healing period to one second, so our protein-based soft robots can now repair themselves immediately,” said lead author Abdon Pena-Francesch. “In nature, self-healing takes a long time. In this sense, our technology outsmarts nature.”

The material uses water and heat to heal, although research leader professor Melik Demirel said it could also use light. When healed after being cut in half, the material reportedly has 100% of its original strength.

A team at the Max Planck Institute for Intelligent Systems in Stuttgart, Germany, created soft actuators for robots that cracked through repetitive use before quickly healing themselves.

The polymer is also biodegradable over time, and can be recycled by using an acid like vinegar to break it down into a reusable powder.

“We want to minimise the use of petroleum-based polymers for many reasons,” said professor Demirel. “Sooner or later we will run out of petroleum and it is also polluting and causing global warming. We can't compete with the really inexpensive plastics. The only way to compete is to supply something the petroleum-based polymers can't deliver, and self-healing provides the performance needed.”

The research was published in Nature Materials.

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