November 2003

Demo: Waterproof Anything

MIT professor Karen Gleason can waterproof just about anything by coating it with an ultrathin layer of Teflon.

By Rebecca Zacks

MIT professor of chemical engineering Karen Gleason is a big fan of Teflon. "Teflon is really an amazing material and has a wide variety of applications," she says. It repels water, it's incredibly slippery, and it's biologically inert, which could make it ideal for coating rain gear, blades for shaving and surgery, and even tiny probes that monitor brain cells during neurosurgery. But the material, she says, "is also limited in the way it has been able to be applied to date." The problem lies not with Teflon itself, Gleason explains, but with the somewhat limited means manufacturers have for attaching it to other materials. Teflon typically starts as a powder, and "they spread the powder, say on a frying pan, and they basically just melt it," she says. The process doesn't create a strong bond between the Teflon and the underlying surface and, because it involves heat, it's useless for very delicate objects. What's more, it produces a coating that's too thick for intricate devices-in the case of a biological probe, thicker than the probe itself. But Gleason has developed a way to tightly bond very thin layers of Teflon to virtually any surface, by growing the long chainlike molecules link by link on the object she wants to coat. She showed Technology Review senior editor Rebecca Zacks how the process works by waterproofing a small sample of the bulletproof textile Kevlar.