Most of us are familiar with that satisfying feeling of pulling dried glue from palms and fingers, where the pull and stretch of the adhesive feels just like real skin. Now, there's a high-tech version: engineers have designed transparent, peel-off artificial skin that stretches just like the real stuff. They described their invention in the journal Nature Materials.

Skin is an amazing thing. It holds your guts in while keeping invaders out. It’s tough, yet flexible, especially on the bodies of young, healthy people. As we get older, our skin loses its elasticity, which leads to sagging and wrinkles. It also becomes thinner and more vulnerable, which makes it easier for bacteria and fungi to cause infection. The same fragile skin can be seen in people with eczema, who may live with intermittent skin infections for their entire lives. 

Between aging and illness, there’s definitely a market for a product that could restore skin’s durability and stretch. But creating something that replicates skin’s many talents has proved a real challenge.

"Creating a material that behaves like skin is very difficult," Barbara Gilchrest, a dermatologist at Massachusetts General Hospital and one of the paper’s authors, said in a press statement. "Many people have tried to do this, and the materials that have been available up until this have not had the properties of being flexible, comfortable, nonirritating, and able to conform to the movement of the skin and return to its original shape." 

Gilchrest and a team of colleagues have been working on the problem for a decade. The criteria were tricky, said MIT biotechnologist and senior author Robert Langer. "It has to have the right optical properties, otherwise it won't look good, and it has to have the right mechanical properties, otherwise it won't have the right strength, and it won't perform correctly.” 

Their solution? Plastics. The researchers decided to create an artificial, skin-like polymer coating that could be applied to the body, rather than making real skin from scratch. In their search for the perfect ingredients, they focused on a chemical compound called siloxane. This combination of oxygen, silicon, and alkane is already widely used by the beauty and food industries to give products a silkier feel and make them more spreadable. 

The researchers built a database of chemical information on more than 100 different siloxane polymers, then tested them to see if any could replicate healthy skin’s stretch, strength, and appearance. (Even the best artificial skin wouldn’t be much use to people if they found it uncomfortable or ugly.)

One siloxane compound emerged as a clear winner. In laboratory tests, this cross-linked polymer layer (XPL) outperformed not only the other compounds, but also human skin. Real, healthy skin can be stretched to about 180 percent of its length and still snap back into shape. The XPL remained elastic even at a 250 percent stretch.

The next step was testing the XPL on real human skin. The researchers conducted three separate small studies to see how XPL stacked up against real skin, as well as other skin treatments. In the first study, the XPL was applied to the baggy under-eye area on one side of women’s faces. In the second, researchers applied the XPL to women’s forearms, then pulled on the skin with suction cups to see how fast it snapped back. A third study tested XPL’s ability to help skin retain moisture (a big challenge for older or eczema-affected skin). 

Researchers applied the XPL to the left side of this woman's face. Image Credit: Olivo Labs, LLC

The artificial skin aced each trial, although its effects were always temporary. It helped firm up the sagging skin under women’s eyes for 24 hours. Forearm skin treated with XPL snapped back faster than untreated skin, and the skin beneath a layer of artificial skin held onto moisture better for up to 24 hours. The “second skin” was off to a good start. The next stage will be testing the XPL on people with eczema to see if it can help.