Scientists have created a material that is flexible during slow motions and impacts, but stiffens upon sudden hits and impacts, according to a Live Science article.

A shear thickening material, it is flexible when moved slowly, but when it is compresssed by an impact, its molecules lock together. The material stiffens, spreading the impact over a greater area. The Swiss company Ribcap is bringing out a new line of headgear for snowsports based on this material. The Ribcap is a combination soft, flexible beanie and tough helmet.

After five years of development, the Ribcap team settled on d3o as the material of choice. Ruth Gough, d3o's brand manager describes her own experience using the Ribcap while out on the piste:

... she [Gough] had a rather dramatic fall that terminated on her head. "I was a bit dazed, and I almost wasn't sure whether I had actually hit my head, although the concern I got from those who saw it assured me that I really had, and quite hard!"

This is a common reaction to real world d3o impact trials. d3o is so comfortable it feels like an extension of you. It's very easy to forget it's there, and you'd be forgiven for thinking, in that split second before you hit the ground "this is never going to work..." (From d3o technology and Ribcap)

Pretty cool.