Abstract

Nano- and microactuators are very small material structures and mechanisms that perform mechanical work in response to external stimuli. The size of these devices can range from a few molecules to several hundred microns. The mechanical action produced by the actuating structure is able to generate tiny displacements or induce microforces on the surrounding medium (Knopf 2006, 2012; Tabib-Azar 1998). Examples of microscale actuators include cantilever beams, microbridges, flexible diaphragms, torsional mirrors, shape memory wires and strips, and expansive polymer gels. These miniature devices may exploit mechanical principles similar to much larger analogous systems or merely involve the subtle expansive and contractive characteristics of environmentally sensitive metals and polymers. In contrast, nanoactuators are often assembled from small groups of interconnected molecules that move in unison under an external energy source. Molecular motor proteins found in living cells are an example of nanoactuators capable of producing piconewton (pN) forces (Kang et al. 2009; Li and Tan 2001; Setou et al. 2000; Vale 2003).