Chemically Controlled Miniature Devices: Microchemomechanical Systems (Adv. Funct. Mater. 13/2011)

A new class of miniature micromechanical devices that do not utilize electricity but respond to different chemical environments are reviewed by David H. Gracias and coworkers on page 2395 . The wireless device shown in the image, for example, opens/closes in response to surface oxidation and reduction. The intellectual motivation to pursue chemically stimulated devices is their wide occurrence in nature. From a practical standpoint, since chemicals can readily diffuse and produce changes over large distances, this approach is especially attractive for very small wireless and autonomous devices. (Image credit: A. Zarafshar and J. Randhawa)