Collaborative Research: Using Boundaries to Create and Control Pathways for Photomechanical Actuation

该奖项支持对保持和约束液晶弹性体的新方法的基础研究，该方法将使薄片在照射时以离散步骤改变形状。液晶弹性体是一类聚合物，当它们被光照射时，可以被定制以经历形状的变化，从而使光直接转换为定向机械功。使用光的一个重要优点是不需要布线、电路和机械触点；由这些材料制成的设备可以远程操作。这一特性可以应用于一系列技术，包括光控显微外科手术工具、集成触摸反馈的显示技术以及利用光进行操作的机器人技术。然而，这些材料产生的机械力很小，并且在光照射时形状的变化难以控制。新的形状变化机制将同时产生快速的响应时间和大的力在形状之间的过渡。因此，本研究的结果可以实现新的设备架构，使这些材料更接近广泛应用，从而使美国经济和社会受益。通过匹兹堡当地组织向代表性不足的K-12学生伸出援助之手，也将与研究项目相结合。在液晶弹性体中观察到的光驱动形状变化可以实现下一代远程驱动执行器。本研究将探讨在边界处应用的光力学自适应与局部约束之间的相互作用。特别是，这种相互作用触发了从先前的平坦状态到非自相似形状的离散过渡的级联。综合实验和建模将用于了解微观结构非均质性、边界条件、材料各向异性和光应变对涌现多晶化和驱动的相互作用。由此产生的对力学的核心贡献将是对具有复杂曲率和非均质性的二维物体的不稳定性和边界条件之间相互作用的更深入的基本理解，使用力学中的壳和膜理论。研究任务包括薄膜样品的合成、光致机械变形的表征、数学模型的建立以及模型的数值分析和解析分析。实验和理论之间的反馈将使预测和准确的模型的制定成为可能，并为实验提供基于物理的指导。

This award supports fundamental research into new ways to hold and constrain liquid crystal elastomers that will cause thin sheets to change shape in discrete steps as the sheets are illuminated. Liquid crystal elastomers are a class of polymers that can be tailored to undergo changes in shape when they are illuminated with light, thereby enabling the direct conversion of light into directed mechanical work. An important advantage of using light is that wiring, circuitry, and mechanical contacts are not needed; devices made of these materials can be operated remotely. This property can enable applications in a range of technologies, including light-operated microsurgical tools, display technologies integrated with touch feedback, and robotics that harness light for manipulation. However, the mechanical force generated by these materials is small and the shape change during irradiation with light is difficult to control. The new shape change mechanisms will simultaneously generate fast response times and large forces during the transition between the shapes. Therefore, the results of this research can enable new device architectures and bring these materials closer to widespread application, thereby benefitting the US economy and society. Outreach to underrepresented K-12 students through local Pittsburgh organizations will also be integrated with the research program. Light-driven shape change observed in liquid crystal elastomers can enable a class of next-generation of remotely-driven actuators. This research will explore the interplay between the photomechanical adaptivity and localized constraints applied at the boundary. In particular, this interplay triggers a cascade of discrete transitions from a prior flat state into non-self-similar shapes. Integrated experiments and modeling will be used to understand the interactions between microstructural heterogeneity, boundary conditions, material anisotropy and photostrains on the emergent multimorphism and actuation. The resulting core contribution to mechanics will be the deeper fundamental understanding of the interplay between instabilities and boundary conditions in two-dimensional objects with complex curvature and heterogeneity, using shell and membrane theories from mechanics. The research tasks include synthesis of thin-film specimens, characterization of light-induced mechanical deformation, development of mathematical models, and numerical and analytical analysis of the models. The feedback between experiment and theory will enable the formulation of predictive and accurate models, as well as provide physics-based guidance to the experiments.