The active ingredient in d3o is a special class of liquid known as shear thickening fluid (STF). For years, STF has been part of soldiers' body armor.
At a recent demonstration for the British Ministry of Defense, d3o employees donned gloves filled with the most reactive d3o ingredient and whacked their hands with hammers. The company walked away with research money for three new projects: shock-absorbing helmets to stop concussions from bullets and explosions, knee and elbow pads, and shock absorbers for solid body armor.
Under normal conditions, STF flows like a liquid, conforming to its container and allowing objects gently placed on top of it to sink in. For an athlete, this means they can move and flex with ease.
Once the pressure is gone, the bonds break and the material becomes soft and flexible once more.
When an object, like a ski gate, slams into -- or sheers -- the fluid, the force of the impact compresses the molecules together and creates very strong, but very temporary bonds between the molecules, and the STF immediately hardens. The tightly-knit molecules spread the impact of the ski gate over the entire area of the pad, instead of the roughly one inch of the ski pole.