Micro-Structured Two-Component 3D Metamaterials with Negative Thermal-Expansion Coefficient from Positive Constituents.
Micro-Structured Two-Component 3D Metamaterials with Negative Thermal-Expansion Coefficient from Positive Constituents.
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DOI：
10.1038/srep40643
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发表时间：
2017-01-12
影响因子：
4.6
通讯作者：
Wegener M
中科院分区：
文献类型：
--
作者：
Qu J;Kadic M;Naber A;Wegener M
控制材料的热膨胀具有重要的技术意义。不受控制的热膨胀可能导致结构和设备的故障或不可逆转的破坏。在普通晶体中，热膨胀由微观结合势的不对称性决定，这是不容易调整的。在被称为超材料的人造晶体中，热膨胀可以通过结构来控制。在这里，根据以前的理论工作，我们制造三维（3D）的两个组件的聚合物微晶格使用灰度激光光刻。我们进行交叉相关分析的光学显微镜图像在不同的样品温度。导出的位移矢量场揭示了双材料梁的热膨胀和由此产生的弯曲导致布置在一个超材料单元内的3D棋盘图案上的3D手性十字的旋转。这些旋转可以补偿所有正成分的膨胀，导致有效地接近零的热长度膨胀系数，或者过度补偿膨胀，导致有效地负的热长度膨胀系数。这证明了惊人的热膨胀控制水平。
Controlling the thermal expansion of materials is of great technological importance. Uncontrolled thermal expansion can lead to failure or irreversible destruction of structures and devices. In ordinary crystals, thermal expansion is governed by the asymmetry of the microscopic binding potential, which cannot be adjusted easily. In artificial crystals called metamaterials, thermal expansion can be controlled by structure. Here, following previous theoretical work, we fabricate three-dimensional (3D) two-component polymer micro-lattices by using gray-tone laser lithography. We perform cross-correlation analysis of optical microscopy images taken at different sample temperatures. The derived displacement-vector field reveals that the thermal expansion and resulting bending of the bi-material beams leads to a rotation of the 3D chiral crosses arranged onto a 3D checkerboard pattern within one metamaterial unit cell. These rotations can compensate the expansion of the all positive constituents, leading to an effectively near-zero thermal length-expansion coefficient, or over-compensate the expansion, leading to an effectively negative thermal length-expansion coefficient. This evidences a striking level of thermal-expansion control.