Algorithm

Materials science

Planar

Computer graphics (images)

Range (aeronautics)

Metamaterial

Thermal expansion

Computer science

Projection (relational algebra)

Scaling

Thermodynamics

Physics

Mathematics

Optics

Thermal

Work (physics)

Geometry

Composite material

Negative thermal expansion

Optoelectronics

Physical Review Letters

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.

Lightweight Mechanical Metamaterials with Tunable Negative Thermal Expansion