Combining Pattern Instability and Shape-Memory Hysteresis for Phononic Switching
Combining Pattern Instability and Shape-Memory Hysteresis for Phononic Switching
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DOI：
10.1021/nl9006112
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发表时间：
2009-05-01
期刊：
影响因子：
10.8
通讯作者：
Thomas, Edwin L.
中科院分区：
文献类型：
--
作者：
Jang, Ji-Hyun;Koh, Cheong Yang;Thomas, Edwin L.
我们报道了由三个步骤组成的二维纳米尺度周期结构的完全可逆和稳健的形状记忆效应，即控制相变的弹性不稳定性，由于玻璃化转变温度(T-g)的升高而锁定转变图案的可塑性，以及由于蒸汽诱导的T-g降低而随后的弹性恢复。交联型环氧树脂/气瓶结构的溶剂溶胀会导致弹性不稳定性，从而导致空洞区域形状从圆形到椭圆形的可逆变化。由于引入了新的滑移对称元素，图案对称性从对称的p6 mm变为非对称的p2gg，并导致声子能带结构发生显著变化，特别是由于能带的反交叉而打开了一个新的窄带隙，这与典型的Bragg散射的带隙截然不同。我们还证明，数值模拟正确地捕捉到了实验观察到的形状记忆循环的三个步骤。
We report a fully reversible and robust shape-memory effect in a two-dimensional nanoscale periodic structure composed of three steps, the elastic instability governing the transformation, the plasticity that locks in the transformed pattern as a result of an increase in glass transition temperature (T-g), and the subsequent elastic recovery due to the vapor-induced decrease in T-g. Solvent swelling of a cross-linked epoxy/air cylinder structure induces an elastic instability that causes a reversible change in the shape of the void regions from circular to oval. The pattern symmetry changes from symmorphic p6mm to nonsymmorphic p2gg brought via the introduction of new glide symmetry elements and leads to a significant change in the phononic band structure, specifically in the opening of a new narrow-band gap due to anticrossing of bands, quite distinct from gaps originating from typical Bragg scattering. We also demonstrate that numerical simulations correctly capture the three steps of the shape-memory cycle observed experimentally.