Photomechanical effect

Photomechanical effect is the change in the shape of a material when it is exposed to light. This effect was first documented by Alexander Graham Bell in 1880. More recently, Kenji Uchino demonstrated that a photostrictive material could be used for legs in the construction of a miniature optically-powered "walker".
The most common mechanism of photomechanical effect is light-induced heating.
Photomechanical materials may be considered smart materials due to their natural change implemented by external factors.