Ultra-low temperature-responsive liquid crystal elastomers with tunable drive temperature range

Abstract

Liquid crystal elastomers (LCEs) have recently gained significant attention in the field of smart materials due to their ability to respond to external stimuli, offering substantial potential for practical applications in soft robotics and bioengineering where actuation and sensing are crucial. However, conventional LCEs typically have high driving thresholds, significantly limiting their practical utility. Thus, reducing the driving temperature of LCEs remains a critical challenge in current research. In contrast to complex chemical molecular modifications aimed at lowering the driving threshold, our work employs a straightforward one-step cross-linking method to synthesize bisacrylate LCEs with varying compositions. These LCEs exhibit remarkably low driving temperatures and improved actuation performance. The monofunctional and difunctional acrylate liquid crystal mixtures employed in our experiments possess different ranges of anisotropy and can be effectively incorporated into the liquid crystal elastomers. Following polymerization, these LCEs demonstrate actuation capabilities at temperatures as low as −18 °C while maintaining excellent performance even at elevated temperatures of up to 60 °C. Moreover, in a series of 50 repeat experiments, the LCEs exhibited exceptional repeatability with a minimal error rate of 2.0 %. Additionally, the introduction of carbon nanotubes into the LCEs resulted in achieving a significant angular deflection of up to 100° within a narrow range of low light intensities, specifically between 26.19 mW cm−2 and 32.38 mW cm−2, highlighting the continued effectiveness of these materials even with this modification.