MIT engineers have developed a breathable hydrogel that could support longer-lasting bandages, implants, cosmetic patches, contact lenses and wearable health sensors.
Hydrogels are soft, water-rich materials used in medical patches, sprays, glues and other products that can stick to skin or be implanted in the body. They are valued for being squishy, stretchy and bio-friendly, but conventional hydrogels have one major limitation: they do not allow air to pass through easily.
When worn for too long, a hydrogel patch or bandage can trap moisture and sweat against the skin. This can irritate tissue and reduce the effectiveness of devices attached with hydrogel adhesives.
The MIT team has now created a hydrogel that remains hydrated while also being aerated. The new material has a network of tiny tunnels running through it, allowing air to move through while maintaining the softness and durability of conventional hydrogels.
“Water and oxygen are both essential for life,” said Xuanhe Zhao, the Uncas and Helen Whitaker Professor of Mechanical Engineering, and a professor of civil and environmental engineering, and medical engineering and science. “Now that we’ve added air to hydrogels, people can find broad applications.”
A typical hydrogel is about 90% water, with the rest made up of polymers that form a scaffold to hold the water in place. That water-heavy structure makes breathability difficult.
“In general, water is not breathable,” said co-lead author Xiao-Yun Yan. “Hydrogel is 80 to 90 percent water, similar to Jell-O. And you cannot breathe through Jell-O.”
To solve the problem, the researchers added a small amount of silica aerogel particles to a conventional hydrogel recipe. The particles helped create interconnected tunnels through the material through a process called viscoelastic phase separation.
“It’s as if the particles formed a network of connected tunnels, like air-permeable highways within the hydrated hydrogel,” said co-lead author Shucong Li.
In tests, volunteers wore wireless electrocardiogram monitors attached with the breathable hydrogel while exercising. The material maintained a strong signal, while conventional commercial hydrogel adhesives showed significant fluctuations. In a 10-day test, volunteers showed no noticeable blisters or redness after removing the monitor.
The team also stretched and compressed the gel 10,000 times. Afterward, it showed less than a 5% drop in oxygen permeability, indicating that the air channels remained intact during repeated movement.
Source: MIT
Image Credit: Felice Frankel
