Courtesy of Dr. Young Sil Lee/U.S. Army Research Laboratory
Kevlar fabric soaked in an experimental fluid stands up to a tough impact.
Vests made of multiple layers of Kevlar fabric are great at stopping bullets, but the material is too heavy, hot, and inflexible to be worn over arms and legs. So the Army Research Laboratory, in collaboration with the University of Delaware, is developing lightweight armor that could shield the whole body.
The secret is a liquid dip that fortifies thin sheets of Kevlar, rendering them nearly impenetrable. Norman Wagner, a chemical engineer at the University of Delaware, developed the strength-enhancing substance after studying liquids whose viscosity or stiffness loosens up when they are stirred or shaken (latex paint, for instance). He then became interested in other liquids that do just the opposite—becoming more resistant when suddenly disturbed—and started experimenting with ways to exploit that property.
By mixing superfine particles of silica glass into various polymer liquids, Wagner created solutions that add strength to Kevlar and other fabrics. When cloth is dipped in the stuff, it stays flexible. But when hit suddenly, the particles in the liquid lock together, forming a stiff, unyielding barrier. In tests, treated Kevlar clothing has withstood vigorous knife and ice-pick attacks. Wagner now hopes to develop versions that can also handle a bullet. Within a year, he expects, his liquid armor could start reinforcing combat uniforms, tents, bomb-muffling blankets, and even sports outfits for civilians seeking extra protection.