Steering with light: indexable photomotility in liquid crystalline polymers

Harnessing light to achieve manipulation and motility in meso and mm-scale systems offers the ability to remotely trigger actuation without requiring on-board power. Central to achieving macroscopic photomotility is the generation of asymmetric interaction between the light-responsive actuator and a substrate. Here, we demonstrate a facile route for achieving indexable, stepped translation of structures fabricated from azobenzene-functionalize liquid crystalline polymers (ALCP). The symmetry breaking in the dynamics of coiling (during irradiation) and uncoiling (when the light is turned off) as a function of the director orientation in splayed ALCP strips leads to asymmetric reaction forces in the interaction with a surface. The broken symmetry leads to directional translation of the center of mass in discrete steps for each on/off cycle of irradiation. Creating composite structures offers a route for hard-coding the trajectories of motility across a range of trajectories that are either rectilinear or curvilinear. Expanding this approach can offer a framework for achieving steerable light-powered microrobots that can translate on arbitrary surface topographies.

在介观和毫米尺度系统中利用光来实现操控和运动，能够远程触发驱动而无需机载电源。实现宏观光致运动的核心是在光响应驱动器和基底之间产生不对称相互作用。在此，我们展示了一种简便的方法，用于实现由偶氮苯功能化液晶聚合物（ALCP）制成的结构的可索引、分步平移。在展开的ALCP条带中，随着指向矢取向的变化，卷曲（照射期间）和解卷曲（光关闭时）动力学中的对称性破缺导致与表面相互作用时产生不对称的反作用力。这种对称性破缺使得在每次照射的开/关循环中，质心以离散的步长定向平移。创建复合结构为在一系列直线或曲线轨迹上对运动轨迹进行硬编码提供了一种途径。扩展这种方法可以为实现可操控的光驱动微型机器人提供一个框架，使其能够在任意表面形貌上移动。