驱动温度可调的依序自滚动液晶弹性体

Sequentially Autonomous Rolling of Liquid Crystalline Elastomers with Tunable Actuation Temperatures

传统的自驱动液晶弹性体,受限于单一的材料化学设计,仅能在特定条件(或温度范围)下实现自主运动.为了解决这一限制,本研究基于扭曲带状的自驱动液晶弹性体,通过调节网络的交联密度和引入非液晶共聚单体的方法,成功实现了对自驱动液晶弹性体工作温度的精确设计.在进一步优化材料的驱动性能和力学性能后,获得了工作温度范围不同的自驱动液晶弹性体,分别实现了不同软体驱动器在升温和降温过程中的按需依次滚动.这种可调工作温度的自驱动液晶弹性体将显著拓展软机器人材料的设计应用领域.

The autonomous liquid crystalline elastomer(LCE)actuators have garnered increasing attention owing to their ability to sustain continuous motion without the need for external manual control.However,most autonomous LCEs are only capable of achieving self-sustained locomotion under specific single conditions(or within a small temperature range)due to their simplistic chemical design.This study begins with a twisted ribbonshaped autonomous LCE,wherein precise control over the working temperature is attained by manipulating the network cross-linking density and incorporating non-liquid crystal co-monomers.The result shows that the crosslinking density has a significant impact on both the actuation performance and mechanical properties of LCEs,thereby influencing working temperature range and actuation speed.Specifically,as the amount of crosslinkers decreases,the actuation strain increases from 60%to 90%while the Young's modulus decreases from 21 MPa to 6 MPa.Due to the compromise of these two properties,the self-rolling capability would be constrained by either excessively high or low levels of cross-linking densities.The optimal performance is observed when the crosslinker ratio is in a moderate state,resulting in a wider range of actuation temperatures and faster moving speed.Beyond that,the incorporation of non-liquid crystal co-monomers also plays an important role in the actuation of LCEs.Different from the cross-linking density,both actuation performance and mechanical properties decrease significantly as the content of co-monomers increases,leading to a notable reduction in the temperature range required for actuation.The phase transition temperature of LCE even disappears when the co-monomer content exceeds 25 wt%,resulting in a loss of autonomous motion.Overall,the aforementioned methods enable the easy achievement of autonomous LCE actuators with diverse working temperature ranges.Sequential autonomous rolling can be accomplished during both the heating and cooling processes,owing to the distinct actuation temperatures exhibited by different LCE actuators.This tunable working temperature of autonomous LCE actuators will significantly broaden the scope of material design for soft robots.