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 two-component polymer microlattices 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 over-compensate the expansion and lead to an effectively negative thermal length-expansion coefficient for all positive constituents evidencing a striking level of thermal-expansion control.
Relaxed micromorphic modeling of the interface between a homogeneous solid and a band-gap metamaterial: new perspectives towards meta-structural design
Programmed Internal Reconfigurations in a 3D-Printed Auxetic Metamaterial Enable Fluidic Control for a Vertically Stacked Valve Array
Department of Biology, College of Arts and Sciences, University of North Carolina at Greensboro（北卡罗来纳大学格林斯伯勒分校文理学院生物系）；The Early College at Guilford（吉福德早期学院）
