Department of Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
Soft Matter. 2016 Jul 20;12(29):6184-95. doi: 10.1039/c6sm00532b.
We investigate mismatch strain driven programmable shape transformation of spherical domes and report the effects of different geometric and structural characteristics on dome behavior in response to applied mismatch strain. We envision a bilayer dome design where the differential swelling of the inner layer with respect to the passive outer layer in response to changes in dome surroundings (such as the introduction of an organic solvent) introduces mismatch strain within the bilayer system and causes dome shape transformation. Finite element analysis reveals that, in addition to snap-through, spherical domes undergo bifurcation buckling and eventually gradual bending to morph into cylinders with increasing mismatch strain. Besides demonstrating how the snap-through energy barrier depends on the spherical dome shape, our analysis identifies three distinct groups of dome geometries based on their mismatch strain-transformed configuration relationships. Our experiments with polymer-based elastic bilayer domes that exhibit differential swelling in organic solvents qualitatively confirm the finite element predictions. We establish that, in addition to externally applied stimuli (mismatch strain), bilayer spherical dome morphing can be tuned and hence programmed through its geometry and structural characteristics. Incorporation of an elastic instability mechanism such as snap-through within the framework of stimuli-responsive functional devices can improve their response time which is otherwise controlled by diffusion. Hence, our proposed design guidelines can be used to realize deployable, multi-functional, reconfigurable, and therefore, adaptive structures responsive to a diverse set of stimuli across multiple length scales.
我们研究了失配应变驱动的球形穹顶可编程形状转变，并报告了不同几何形状和结构特征对穹顶响应施加失配应变的行为的影响。我们设想了一种双层穹顶设计，其中内层相对于被动外层的不同膨胀，以响应穹顶周围环境的变化（例如引入有机溶剂），会在双层系统中引入失配应变，并导致穹顶形状的转变。有限元分析表明，除了突跳外，球形穹顶还会经历分岔屈曲，最终随着失配应变的增加逐渐弯曲成圆柱。除了展示突跳能垒如何取决于球形穹顶的形状外，我们的分析还根据它们的失配应变转换配置关系确定了三类不同的穹顶几何形状。我们使用聚合物基弹性双层穹顶进行的实验，这些穹顶在有机溶剂中表现出不同的膨胀，定性地证实了有限元预测。我们确定，除了外部施加的刺激（失配应变）之外，双层球形穹顶的形态还可以通过其几何形状和结构特征进行调整和编程。在响应性功能器件的框架内引入弹性不稳定性机制（如突跳）可以改善它们的响应时间，否则响应时间由扩散控制。因此，我们提出的设计准则可以用于实现可展开、多功能、可重构的自适应结构，以响应多种不同长度尺度的刺激。
