Photo-induced spatiotemporal bending of shape memory polymer beams
Photo-induced spatiotemporal bending of shape memory polymer beams
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DOI：
10.1088/1361-665x/ac9d75
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发表时间：
2022-10
影响因子：
4.1
通讯作者：
Boliang Wu;Tianzhen Liu;Yuzhen Chen;Lihua Jin
中科院分区：
文献类型：
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作者：
Boliang Wu;Tianzhen Liu;Yuzhen Chen;Lihua Jin
在外界刺激下，如热、光或磁场，刺激响应软材料可以通过非平衡动力学过程，包括反应、扩散和粘弹性弛豫，将其当前结构改变为新的平衡状态，从而产生新的时空形状变形行为。本文以光热形状记忆聚合物（SMP）悬臂梁为模型系统，对其在光照下的非平衡动力学过程和时空弯曲进行了分析、数值和实验研究。我们建立了SMPs的热力学模型，该模型捕捉了传热和粘弹性松弛的非平衡过程，该过程通过梁的厚度引起非均匀的温度和应变分布，导致其弯曲和不弯曲。通过改变关键的无量纲参数，我们从理论上和实验上观察到不同类型的弯曲动力学。此外，我们的理论考虑了由于光束广泛弯曲引起的入射角变化，并证明了这种影响会由于有效光强的降低而大大延迟弯曲，并进一步通过实验验证了这一点。这项工作展示了SMP的可编程和可预测的时空变形，并为SMP变形结构和机器人提供了设计指南。
In response to external stimuli, such as heat, light, or magnetic fields, stimuli-responsive soft materials can change their current configuration to a new equilibrium state through non-equilibrium kinetic processes, including reaction, diffusion, and viscoelastic relaxation, which generates novel spatiotemporal shape-morphing behavior. Using a photothermal shape memory polymer (SMP) cantilever beam as a model system, this work analytically, numerically, and experimentally studies its non-equilibrium kinetic processes and spatiotemporal bending under light illumination. We establish a thermomechanical model for SMPs capturing the concurrent non-equilibrium processes of heat transfer and viscoelastic relaxation, which induces inhomogeneous temperature and strain distributions through the thickness of the beam, resulting in its bending and unbending. By varying the key dimensionless parameters, we theoretically and experimentally observe different types of bending dynamics. Moreover, our theory takes into consideration changes in the angles of incidence caused by extensive beam bending, and demonstrates that this effect can dramatically delay the bending due to reduction of the effective light intensity, which is further validated experimentally. This work demonstrates programmable and predictable spatiotemporal morphing of SMPs, and provides design guidelines for SMP morphing structures and robots.