Mesoscale Photomechanical Coupling in Photoactive Liquid Crystal Elastomers

该奖项将支持基础研究，以研究光、力学和化学在光活性液晶弹性体中的耦合。这项研究将在纳米分子和宏观材料之间架起一座桥梁。光活性液晶弹性体是一种由液晶分子组成的橡胶材料，液晶分子对光的响应会发生大的变形。然而，与单个光活性分子相比，现有的宏观光活性材料的性能并不理想。这项研究将结合理论和实验方法，填补单分子行为和宏观性能之间的理解空白。该项目将通过提供新的机会从光中获取能源，从而使经济和社会需求受益。潜在的新应用包括极端环境下的光驱动机器人系统。此外，该项目将对研究生和本科生的教育和培训产生更广泛的影响。他们将在国际和平研究所的实验室进行研究培训，并开设一门关于软活性材料的新课程。还将支助几项组织良好的外联活动。这些活动包括高中夏令营和科学实地考察，重点是让未被充分代表的人群参与STEM。本研究的目的是通过建立受光照明和机械载荷作用的光活性液晶弹性体的微观力学理论框架和多物理实验平台，了解中尺度光机械耦合的基本机制。微观力学理论将从单分子光反应和多个相互作用的液晶分子的统计物理中提取信息，并将其整合到连续介质力学模型中。为了验证理论模型，在实验中将制备不同组成的光活性液晶弹性体样品，在实验中将表征其在规定的光照、温度和机械应力下的宏观行为。与这些因素相关的基本机制将被研究，以优化材料的光驱动功输出，并通过调节液晶分子的介观尺度分子排列来开发新的光机械驱动方法。宏观变形和功输出将通过利用材料相变和机械不稳定性得到进一步增强。该奖项反映了NSF的法定使命，并已通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This award will support fundamental research to investigate the coupling between light, mechanics, and chemistry in photoactive liquid crystal elastomers. This research will bridge the length scales between a nanoscale molecule and a macroscale material. Photoactive liquid crystal elastomers are rubbery materials composed of liquid crystal molecules that undergo large deformation in response to light. However, compared to an individual photoactive molecule, existing macroscopic photoactive materials do not perform as well. This research will combine theoretical and experimental approaches to fill the gap in understanding between single molecule behavior and macroscopic performance. This project will benefit the economic and societal needs by enabling new opportunities to harvest energy from light. Potential new applications include light-driven robotic systems for extreme environments. In addition, the project will have broader impacts in the education and training of graduate and undergraduate students. They will be engaged in research training in the PI’s lab and a new course on soft active materials. Several well-organized outreach activities will also be supported. These include high school summer camps and science field trips with a strong focus on engaging underrepresented populations in STEM.The objective of this research is to understand the fundamental mechanics of mesoscale photomechanical coupling, by building a micromechanical theoretical framework and a multiphysics experimental platform for photoactive liquid crystal elastomers subjected to both light illumination and mechanical load. The micromechanical theory will extract information from the single-molecule photoreaction and the statistical physics of many interacting liquid crystal molecules and integrate it into a continuum mechanics model. To assess the theoretical model, samples of photoactive liquid crystal elastomer will be fabricated with different compositions in experiments, where their macroscopic behaviors subjected to prescribed light illumination, temperature, and mechanical stress will be characterized. The fundamental mechanisms related to these factors will be investigated to optimize the light-driven work output by the material and develop new ways of photomechanical actuation through tuning the mesoscale molecular alignment of liquid crystal molecules. The macroscopic deformation and work output will be further enhanced by harnessing material phase transformation and mechanical instability.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.