DAVIS, CALIFORNIA--Designed for commandos, a new wetsuit automatically adjusts to keep divers warmer in cold water. The underlying technology could have other uses in sports, such as smoothing out the swimsuits of competitive swimmers.
As its name implies, a wetsuit lets in water that then insulates the body. The idea works fairly well, but it has a limitation: Warmed water leaks out and cold water sneaks in. Such "flushing" accounts for up to 60% of a diver's heat loss, so to counteract the cooling, manufacturers make wetsuits thicker. They also employ tight-fitting gussets around the wrist, ankles, and neck. But those measures make a suit more cumbersome and uncomfortable.
In contrast, the new high-tech suit shuts off the flow of water when it gets cold by swelling to fill in the gaps between diver and suit, reports engineer Alec Jessiman of Midé Technology Corp. in Medford, Massachusetts. The key to the suit is a new material called SmartSkin, designed by Jessiman and colleagues at Midé and the Massachusetts Institute of Technology in Cambridge. Between two protective layers of fabric lie an outer layer of neoprene--the same stuff conventional wetsuits are made of--and an inner layer of urethane foam. The foam is impregnated with a polymer called a "hydrogel" that can absorb many times its original volume of water.
The researchers tuned the gel to absorb 20 to 30 times its original volume of water when temperatures dipped below 20°C. Tank tests showed that in 25° water the suit was as cool as a conventional suit. But at 17° it lost 70% less heat than the conventional suit, Jessiman reported here 14 September at the 5th International Conference on the Engineering of Sport. The suit absorbed or expelled the excess water reversibly in about a minute.
Midé developed the suit for the U.S. Navy's commandos, the SEALs, but hopes to license the technology for the consumer market. In the meantime, the swelling gel may have other interesting sports applications, says aerodynamicist Len Brownlie of Aerosports Research in West Vancouver, Canada. For instance, it might be built into high-tech swimsuits to fill in the depressions and hollows of the body that create turbulence and drag. Of course, Brownlie says, that's if the rules of competitive swimming will allow it.
The 5th International Conference on the Engineering of Sport 
Midé Technology Corp.