The material is a mixture of hyaluronic acid and polyethylene glycol. The acid is already approved for use as a soft-tissue implant, and glycol, or "PEG" as it's known, is a material that has uses in manufacturing, the beauty industry, and medicine. When blended, the two liquids create a biomaterial--partly synthetic, partly biological--that's a polymer, one that's fluid enough to be injected.
Surgeons would inject the biomaterial into the skin and massage the features into the desired shape. By exposing the material to bright-green LED light (bright enough to penetrate skin up to four millimeters thick), the polymer molecules change their properties and tangle to form a rigid structure, setting the shape of the implant permanently.
This means big changes for patients suffering from facial disfiguration, a highly visible injury that can have social consequences. But that's just the most obvious use. If the material becomes a commercial product, we could see a wealth of potential customers among the extreme body-modification set. After all, the idea of reliably adding semi-permanent Klingon-like bumps to your face with a simple injection (a far less risky and expensive process, perhaps, than full-on plastic surgery) will definitely interest some people.
It's been tested on rats, and in a very limited form on humans too, with very positive results and only minor side effects. A full-scale human test is upcoming, and the only issue so far is that the material degrades at a rate that could mean re-injections are needed every year or so--but the team thinks new tissue may actually grow into the implants in time.