Liquid Body Armor

This technology makes significant headway into protecting soldiers' lives

Liquid armor for Kevlar vests is one of the newest technologies designed to save soldiers' lives that's been under development by the U.S. Army Research Laboratory. This type of body armor is light and flexible, allowing soldiers to be more mobile while they're still protected. It doesn't hinder an individual when running or aiming his or her weapon.

The Components of Liquid Armor 

The key component of liquid armor is a sheer thickening fluid or STF.

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

STF is soaked into all layers of a Kevlar vest to make liquid armor. 

How Liquid Armor Reacts

The Kevlar fabric holds the STF in place and it also helps to stop bullets. The saturated fabric can be soaked, draped, and sewn just like any other fabric.

During normal handling, the STF is very deformable and flows like a liquid. But when a bullet or frag hits the vest, it transitions to a rigid material. This prevents the projectile from penetrating the soldier's body, according to Dr. Eric Wetzel, a mechanical engineer from the Weapons and Materials Research Directorate who heads the U.S. Army project team.

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

The Goal of the Technology 

The goal of the technology is to create a new material that is low cost and lightweight while still offering equivalent or superior ballistic properties compared to current Kevlar fabric.

But liquid armor also has more flexibility and less thickness, according to Wetzel. The 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 is 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 used 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."

Wetzel and his team have been awarded the 2002 Paul A. Siple Award, the Army's highest award for scientific achievement, for their work on liquid armor.

By Tonya Johnson, Army Public Affairs