Something unexpected happened when scientists at the University of California, Riverside, started stringing together nanoparticles of gold.
The gold wasn't golden anymore. It changed colors.
"When we see these gold particles aggregate, we find out they have very, very beautiful blue colors," chemist Yadong Yin told me. That bright blue would dissipate like a sunset—morphing into purple, then red—when scientists warped the strings, breaking apart the nanoparticles.
The finding was one of those happy scientific accidents that turns into something bigger. "So after we found out the reason why they show blue colors and what the structure was, then we started to think what kind of use they could have," Yin said.
What Yin and his colleagues came up with: Sensors made of gold nanoparticles that change colors as you press on them. Think of it as a Hypercolor—those color-changing T-shirts all the cool kids had in the '90s—but for touch instead of heat. But rather than using color-changing sensors for fashion, Yin and his team see them as the perfect tool for making better crash-test dummies. The sensors can be painted on or applied like a bandage, and they convey differences in pressure at certain points of impact.