Reuters video screenshot by Leslie Katz/CNET

Faced with the threat of bullet fire, most people probably won't be giving much thought to the material inside their bulletproof vest. But better believe they'll care that it offers improved protection.

That's what Moratex Institute of Security Technologies is promising from an unlikely substance -- liquid. The Polish company is the latest to test a shear-thickening fluid, or STF, which it says not only is lighter and more flexible than standard anti-ballistic materials, but provides a hardier barrier.

"Even in cases when there is no penetration through the protective layer, the user can lose their life, or be badly injured," Marcin Struszczyk, deputy director of the research institute, says of bulletproof gear in a Reuters report. "Thanks to the liquid's properties, we eliminate 100 percent of this threat, because we've reduced the deflection from 4 centimeters to 1 centimeter."

Reduced deflection means, simply, that ammunition fired at the barrier won't penetrate as deeply, clearly an advantage for anyone who's been hit.

For now, the company isn't saying exactly what's in the fluid, but "when fitted in a vest, it stops bullets fired at 450 meters [about 1,476 feet] per second, and prevents the often-lethal ricochets that can occur whilst wearing similar protection," Reuters says in its video report.

The liquid is non-Newtonian, meaning it doesn't dissipate when met with force, or shear. Instead, it hardens.

"This liquid is different from others in that its viscosity changes with the increases in applied force," Karolina Olszewska, who performed tests on the fluid for Moratex, says in the video. Moratex says it "won't be long" before police and military forces can purchase the product.

The Polish research institute isn't the first to dabble in the liquid-armor space. In 2010, Britain's BAE Systems announced a new, lighter bulletproof material that combines Kevlar and shear-thickening fluid, which also shows promise beyond the battlefield as a potential material in sports gear, car bumpers and road barriers.

"When combined with Kevlar, the reduced flow of the fluids in the liquid armor restricts the motion of the fabric yarns. This means an increase in area over which the impact energy is dispersed," BAE explains. "The material is therefore far less likely to distort than standard body armour, which generally bends inwards when a bullet strikes, preventing death, but causing considerable pain."

Advances in liquid armor first emerged from the University of Delaware in the early 2000s. Since then, the university has worked with scientists at the US Army Research Laboratory on body protection that relies on ceramic nanoparticles suspended in thickening fluid to stop bullets, knives or shrapnel.

University of Delaware

Like the shear-thickening fluid from Moratex, the substance the university developed hardens instantly when hit or shaken. Once that stress stops, the body armor returns to its flexible state. The university has trademarked its patented innovation, called Liquid Armor, and sees potential beyond the battlefield.

"For first responders, you get not only ballistic protection with Liquid Armor, but you also gain this additional stab and puncture protection," said Norman Wagner, a professor of chemical engineering at the UD who co-created the substance with Eric Wetzel, an engineer at the US Army Research Laboratory. "And the material can do all of this while increasing the vest's wearability."

Wagner and team are working on high-tech, puncture-resistant gloves to protect medical professionals from cuts and needle sticks that could lead to the transmission of hepatitis and HIV. "Puncture is a real issue" in health care, says Wagner, who in 2013 started a company, STF Technologies, to work on the product. His team is also teaming with spacesuit manufacturer ILC Dover on other possible applications.

Contacted by CNET last week, Wagner said he was unfamiliar with the work being done at Moratex, "but it seems this group is making progress."