Hydrogels are squishy, bio-friendly materials that are made mostly of water and a bit of polymer. The Jell-O-like substance is available in the form of medical patches, sprays, and glues, and can be stuck to the skin or implanted in the body to dress wounds, affix implants, and encapsulate and release medicine over time. For all their sticky, stretchy, and protective properties, hydrogels lack one key trait: breathability. If worn for too long, a bandage or patch can trap moisture and sweat, which can irritate tissues and reduce the effectiveness of any device that a hydrogel adheres. Now MIT engineers have come up with a recipe for a hydrogel that is both hydrated and aerated, or permeable to air. The new material is just as soft, stretchy, and robust as conventional hydrogels, but a network of tiny tunnels running through the gel allows air to pass through. The aera…

These hydrogels end up having a greater balance of polymer to water, making them less hydrated in general. Zhao, who has been a leader in the development and application of hydrogels, looked to make a hydrogel that lets air through without losing its water-heavy makeup. “We want to have lots of tiny channels to let air through, while also maintaining lots of water in the gel,” Zhao says. “This was a significant challenge, and something that people thought was impossible to do.” After several years of investigation, the team hit on an ideal recipe for a breathable hydrogel that minimizes the non-water ingredients needed to let air through. In their new study, they report that the key to the recipe is “phase separation.” A common example of this process is the interaction between oil and water. The difference in the two liquids’ phases cause them to instantly separate.…