This squid-inspired protein is the future of PPE

Cephalopods may hold the secret to damage-resistant PPE.

As Covid-19 infections continue to spread, the importance of keeping a clean mask with you at all times is unparalleled. But after repeated wear and washing, these masks can become tattered and leave you exposed to the virus through tiny, threadbare holes.

Scientists are looking to solve this problem before it becomes commonplace by synthesizing special proteins found in squids to create a self-healing material that can extend the life of both masks and ventilators.

In a study published Monday in the journal Nature Materials, a team of material scientists and engineers from Germany, Turkey, and Penn State describe how they were able to transform unique squid proteins into a soft, biodegradable material that could be used to develop soft robots — and tear-resistant personal protective equipment (PPE).

Self-healing material itself is not novel to the field, but existing self-healing materials can take up to 24-hours to heal and have a much lower overall resilience to damage, the researchers explain.

Their new squid-inspired material, on the other hand, can withstand tears and cuts and heal damage in just one second — while maintaining 100 percent of its previous strength.

From its humble beginning as a squid protein, this synthetic mimic can be used to build everything from PPE to robotic limbs.

Nature Materials

Abdon Pena-Francelsch, the study's first author and former Penn State doctoral student, said in a statement that transforming these natural proteins for material uses allows them to even outdo nature.

"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 Pena-Francelsch. "In nature, self-healing takes a long time. In this sense, our technology outsmarts nature."

How does it work — Mimicking a protein found in squid ring teeth, the team developed a synthetic protein that was composed of so-called "tandem repeats," or sections of the DNA that were repeated.

By controlling how these repeats occurred in the protein, the team was able to create an incredibly strong cross-linked network of proteins. Like velcro that can be pulled apart and seamless stuck back together, the order of DNA repeats in these proteins makes their molecular network incredibly resilient to permanent damage.

Melik Demirel, a co-author of the study and Huck Chair of Biomimetic Materials at Penn State, tells Inverse that despite its resilience, this wound healing is not autonomous.

"It is not self-activated," says Demirel. He explains that in order to spark regeneration, the material needs either water or pressure. "We envision that the method can be performed with light in the future."

Small puncture wounds in this material can be self-healing using water and pressure stimulation in just a single second.

Nature Materials

What were the results — In order to test the resilience of their new material, the team ran it through a series of trials, including being torn or cut and using it to fabricate human-like muscles that could deadlift 3,000 times its own weight.

Compared to other self-healing materials that can take upwards of 24-hours to heal, the researchers found that their material was able to recover from damage in only a single second, making it much more resilient in situations like hospitals where a tear in a piece of PPE could be deadly in a matter of minutes.

The team also found during their trials that the material was able to regain 100 percent of its strength after being repaired, as opposed to other materials which would lose a little bit of their strength with each repair cycle.

In addition to creating resilient PPE, the authors say that this material could also be used to create wear-resistant soft robots or even prosthetic limbs.

The future of PPE — In addition to developing light-based approaches to initiate the material's self-healing, the team is also working to scale the process in the coming years, Demirel says. The goal is to develop products, like prosthetics or PPE, for environments beyond the lab.

Part of what is exciting about this possibility is the opportunity for biodegradable and green technology that using this material would enable, Demirel explains. Unlike polymer-based materials that are hard to degrade, this biomimetic material can be dissolved quickly in a simple acid like vinegar.

"From the environmental perspective squid proteins not only provide a new performance but also bring circularity," Demirel says. "Future masks or ventilators can be green as well as have high performance."

Abstract: Self-healing materials are indispensable for soft actuators and robots that operate in dynamic and real-world environments, as these machines are vulnerable to mechanical damage. However, current self-healing materials have shortcomings that limit their practical application, such as low healing strength (below a megapascal) and long healing times (hours). Here, we introduce high-strength synthetic proteins that self-heal micro- and macro-scale mechanical damage within a second by local heating. These materials are optimized systematically to improve their hydrogen-bonded nanostructure and network morphology, with programmable healing properties (2–23 MPa strength after 1 s of healing) that surpass by several orders of magnitude those of other natural and synthetic soft materials. Such healing performance creates new opportunities for bioinspired material design, and addresses current limitations in self-healing materials for soft robotics and personal protective equipment.
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