A semi-fast artificial muscle

Katchalsky's (1949) idea for an artificial muscle was based on a gel swollen by a chemical effector (pH, ions, etc.). This scheme has two major defects: a) long response times (controlled by diffusion); b) fractures are often induced by the inhomogeneous mechanical tensions present at intermediate stages. We propose here another scheme, based on the lamellar phase of a triblock copolymer RNR (R =elastomer, N = nematogenic backbone). When the composite resulting from cross-linking the elastomer is exposed to a pulse of light (in a suitable adsorption band) it should go rapidly and homogeneously from the nematic to the isotropic state. It then quickly contracts (via acoustic waves from both ends). The reverse process (by cooling) is slow and inhomogeneous, but the composite structure should be rather robust.