Mechanical Adaptability for Light-Responsive Liquid Crystal Networks via Incorporating Acrylic Acid

Abstract

The field of soft robotics has gained huge interest in the field of robotics due to the versatility, compliance and flexibility of soft actuators compared to their rigid counterparts. Liquid crystal networks (LCNs), especially light-responsive LCNs provide a promising platform for designing soft actuators due to their excellent high deformation ability and mechanical properties. Mechanical adaptability, i.e., spontaneous change in mechanical properties in response to changes in the surrounding conditions, of LCN-based soft actuators is a convenient feature to be considered when designing a soft robot. Such feature provides the ability to function in different environmental conditions with different constraints to the mechanical properties of the actuator. Here, liquid crystal (LC) mixtures were prepared with varied molar ratios of acrylic acid. Phase transition points were identified for the LC mixtures. Selected LC mixtures were polymerized to prepare light-responsive LCN films. Characterization of these films as well as investigation of their mechanical adaptability were carried out. The results showed that the mechanical adaptability capacity increased as the monomer-to-acrylic-acid molar ratio (MAA) decreased. However, the downside was that the overall mechanical strength and the nematic alignment of the films were reduced. LCN films with MAA of 1:1 and 1:2 possessed the best balance of efficient mechanical adaptability while maintaining good mechanical strength and nematic alignment. Optimizing the molar ratios of acrylic acid and investigating other techniques of incorporating acrylic acid into the network is an important next step to this work. Furthermore, this work can open the possibility of designing a mechanical adaptable light-responsive soft robot.