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Water-based hydrogel does not dry out, scientists say

Scientists at MIT think the material could be used for wound dressings or human-like skin on robots.

By Stephen Feller
Engineers at MIT have found a way to prevent hydrogels from dehydrating, with a method that binds hydrogels to elastomers such as rubber and silicone, pictured above. Screenshot via Melanie Gonick/Massachusetts Institute of Technology/YouTube
Engineers at MIT have found a way to prevent hydrogels from dehydrating, with a method that binds hydrogels to elastomers such as rubber and silicone, pictured above. Screenshot via Melanie Gonick/Massachusetts Institute of Technology/YouTube

CAMBRIDGE, Mass., June 27 (UPI) -- Late last year, scientists at the Massachusetts Institute of Technology created a "smart wound dressing" made of a hydrogel, but found it dried out over time.

The same research team found a rubbery substance called elastomer could coat the hydrogel and keep it stretchy and wet over time, potentially finding an even more effective, skin-like material in the process, researchers report in Nature Communications.

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The idea of coating hydrogels to prevent them from drying out comes from skin, which has two layers -- the epidermis, which acts a shield, blocking the network of nerves, capillaries and other parts of the dermis from exposure to the elements.

"It is a thought-provoking work," Syun-Hyun Yun, an associate professor at Harvard Medical School and Massachusetts General Hospital who was not involved in the research, said in a press release. "Among many [applications], I can imagine smart artificial skins that are implanted and provide a window to interact with the body for monitoring health, sensing pathogens, and delivering drugs."

After trying and failing with salt and with another method for bonding elastomers to solid surfaces, the researchers coated a sheet of elastomer in benzophenone and then wrapped it around a sheet of hydrogel, exposing it to UV light to activate the benzophenone and seal the two polymers together.

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The weight of the hybrid material did not change after 48 hours, suggesting it had not dried out at all, and the force needed to peel the two sheets apart was much higher than what is required to separate the epidermis from the dermis.

In further tests, the researchers were able to simulate a network of blood vessels between the hydrogel and elastomer, flowing red, blue and green food coloring through the channels, suggesting it could be developed into a drug-delivering bandage.

The researchers also were able to control an LED light through the hydrogel, suggesting it may also be conductive -- further widening the material's potential.

"We hope this work will pave the way to synthetic skin, or even robots with very soft, flexible skin with biological functions," said Dr. Zuanhe Zhao, the Robert N. Noyce Career Development Associate Professor in the department of mechanical engineering at MIT and lead engineer on the project.

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