Electromechanical Response in Liquid Crystal Gels and Networks

The uniqueness of liquid crystals (LCs) lies in the large anisotropies in their properties, which can be utilized to generate high electromechanical responses. In a properly oriented liquid crystal polymer system, an external electric field can induce re-orientation of the mesogenic units possessing a dielectric anisotropy, which, when coupled with the shape anisotropy of the mesogenic units, can in turn produce large mechanical strain. Anisotropic liquid crystal gels, which can be obtained by in situ photopolymerization of the reactive LC molecules in the presence of non-reactive LC molecules in an oriented state, are an example of such liquid crystal polymer systems. It has been shown that a homeotropically aligned liquid crystal gel in its nematic phase exhibits high electrically induced strain (>2%) with an elastic modulus of 100MPa and a high electromechanical conversion efficiency (75%) under an electric field of 25 MV/m. These anisotropic LC polymeric materials could provide a technologically compatible system for such applications as artificial muscles and as micro-electromechanical devices.