Light Makes New Material Creep Like a Caterpillar

It's aliiiiiiive! Well, maybe not. But when activated by light, a new type of polymer — a

material made of long chains of molecules — can inch along just like a caterpillar. Scientists developed the light-sensitive substance and coaxed a small strip of it to "walk" by exposing it to a fixed light source.The spotlight made one side of the paper-clip-sized material contract while the other side expanded, producing an undulating movement that carried it forward, the researchers reported in a recent study. [Science Fact or Fiction? The Plausibility of 10 Sci-Fi Concepts] The secret to this groundbreaking light-activated locomotion lies in the liquid crystal network (LCN) in the polymer. LCNs are known for their ability to deform materials when exposed to light, but prior studies had only examined their ability to warp materials, not move them forward or backward, the scientists wrote in the study. To determine whether bending could become walking, researchers tweaked chemical components in their polymer's LCN to make it relax more quickly after contracting, which would translate into a smoother, more wavelike motion in the polymer. Then, as the polymer strip deformed, the shadows it threw over itself created a feedback loop in the wave — contracting and expanding repeatedly, as the light intensity changed — which made the polymer "walk," the study authors reported. To further test their tiny walker, the researchers placed sand grains on the material, which it successfully transported through its wavelike movements — and it was able to do this over and over again, the scientists wrote.