Kevlar fabric with shear thickening fluid, after impact by a fragment simulating projectile.

This type of body armor is light and flexible, which allows soldiers to be more mobile and won't hinder an individual from running or aiming his or her weapon.

The key component of liquid armor is a shear thickening fluid. STF is composed of hard particles suspended in a liquid. The liquid, polyethylene glycol, is non-toxic, and can withstand a wide range of temperatures. Hard, nano-particles of silica are the other components of STF. This combination of flowable and hard components results in a material with unusual properties.

"During normal handling, the STF is very deformable and flows like a liquid. However, once a bullet or frag hits the vest, it transitions to a rigid material, which prevents the projectile from penetrating the Soldier's body," said Dr. Eric Wetzel, a mechanical engineer from the Weapons and Materials Research Directorate who heads the project team.

To make liquid armor, STF is soaked into all layers of the Kevlar vest. The Kevlar fabric holds the STF in place, and also helps to stop the bullet. The saturated fabric can be soaked, draped, and sewn just like any other fabric.

Wetzel and his team have been working on this technology with Dr. Norman J. Wagner and his students from the University of Delaware for three years.

"The goal of the technology is to create a new material that is low cost and lightweight which offers equivalent or superior ballistic properties as compared to current Kevlar fabric, but has more flexibility and less thickness," said Wetzel. "This technology has a lot of potential."

Liquid armor is still undergoing laboratory tests, but Wetzel is enthusiastic about other applications that the technology might be applied to.

"The sky's the limit," said Wetzel. "We would first like to put this material in a soldier's sleeves and pants, areas that aren't protected by ballistic vests but need to remain flexible. We could also use this material for bomb blankets, to cover suspicious packages or unexploded ordnance. Liquid armor could even be applied to jump boots, so that they would stiffen during impact to support Soldiers' ankles."

In addition to saving Soldiers' lives, Wetzel said liquid armor in Kevlar vests could help those who work in law enforcement.

"Prison guards and police officers could also benefit from this technology," said Wetzel. "Liquid armor is much more stab resistant than conventional body armor. This capability is especially important for prison guards, who are most often attacked with handmade sharp weapons."

For their work on liquid armor, Wetzel and his team were awarded the 2002 Paul A. Siple Award, the Army's highest award for scientific achievement, at the Army Science Conference.