Material science is making its usual unheralded contribution to health and safety. In this case, it's liquid armor. It's a liquid filling to put inside armor or even normal clothing items like boots that remains light and flexible in normal use but stiffens immediately to rigidity under sudden stress. After the stress goes away, it softens right up again. Not only is liquid armor useful in areas like limbs than kevlar with rigid plates it also has potential civilian uses like a steel toed boot replacement.
It also has the advantage of being better against stab wounds than regular body armor, a must for law enforcement/penal operations.
HT: defensetech