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，这种方法将导致薄片在照射时以离散的步骤改变形状。液晶弹性体是一类聚合物，可以定制成在用光照射时发生形状变化，从而使光能够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、电路和机械接触；由这些材料制成的设备可以远程操作。这一特性可以使一系列技术得到应用，包括光操作的显微外科工具、与触摸反馈集成的显示技术，以及利用光进行操纵的机器人。然而，这些材料产生的机械力很小，在用光照射时形状变化很难控制。新的形状变化机制将在形状之间的转换过程中同时产生快速响应时间和强大的力。因此，这项研究成果可以使新的器件架构成为可能，并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不足的K-12学生提供服务也将与研究计划相结合。在液晶弹性体中观察到的光驱动形状变化可以实现一类远程驱动的下一代执行器。这项研究将探索光机械适应性和应用于边界的局部约束之间的相互作用。具体地说，这种相互作用触发了从先前平面状态到非自相似形状的离散转变的级联。综合的实验和模拟将被用来理解微结构的非均质性、边界条件、材料的各向异性和光应变之间的相互作用对突现的多晶性和驱动。由此产生的对力学的核心贡献将是使用力学中的壳和膜理论，对具有复杂曲率和非均质性的二维物体中不稳定性和边界条件之间的相互作用的更深层次的基本理解。研究任务包括薄膜样品的合成，光诱导机械变形的表征，数学模型的建立，以及模型的数值分析和分析。实验和理论之间的反馈将使建立预测和准确的模型成为可能，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.