Photopatterned liquid crystalline polymers for microactuators

Abstract

We have investigated the properties of thermally-responsive, patterned liquid crystalline polymers as their dimensions are scaled to a size suitable for use in microelectromechanical systems. All samples were fabricated using surface alignment and photopatterning techniques that can be used to produce integrated devices anchored on a substrate. The thermomechanical properties of free-standing macroscopic samples with varying concentration of crosslinking molecules were investigated in order to optimize the thermal response of the material. It was found that samples containing 12% crosslinker were able to expand by up 19% when heated. The thermomechanical properties of surface-anchored films were also investigated, and it was found that by employing a polymerized cholesteric structure of the liquid crystalline units a thermal expansion of up to 11% could be achieved when the sample was heated to 200 °C. Patternability was demonstrated using a simple photopatterning process that was used to fabricate samples consisting of lines of cholesteric material on a bare substrate, or alternating regions of liquid crystalline polymer in the isotropic and cholesteric phases. Actuation of these films was also demonstrated.