Lightweight Mechanical Metamaterials with Tunable Negative Thermal Expansion.
Ice floating on water is a great manifestation of negative thermal expansion (NTE) in nature. The limited examples of natural materials possessing NTE have stimulated research on engineered structures. Previous studies on NTE structures were mostly focused on theoretical design with limited experimental demonstration in two-dimensional planar geometries. In this work, aided with multimaterial projection microstereolithography, we experimentally fabricate lightweight multimaterial lattices that exhibit significant negative thermal expansion in three directions and over a temperature range of 170 degrees. Such NTE is induced by the structural interaction of material components with distinct thermal expansion coefficients. The NTE can be tuned over a large range by varying the thermal expansion coefficient difference between constituent beams and geometrical arrangements. Our experimental results match qualitatively with a simple scaling law and quantitatively with computational models.
Sonny Astani Department of Civil and Environmental Engineering, University of Southern California, Los Angeles, California 90089, USA.
Qiming
Q
Wang
Lawrence Livermore National Laboratory, Livermore, California 94550, USA.
Julie A
JA
Jackson
Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.|Digital Manufacturing and Design Centre, Singapore University of Technology and Design, 487372, Singapore.
Qi
Q
Ge
Department of Mechanical and Aerospace Engineering, University of California, Los Angeles, California 90095, USA.
Jonathan B
JB
Hopkins
Lawrence Livermore National Laboratory, Livermore, California 94550, USA.
Christopher M
CM
Spadaccini
Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Nicholas X
NX
Fang