Lightweight Mechanical Metamaterials with Tunable Negative Thermal Expansion

Area of Science:

• Materials Science
• Metamaterials
• Mechanical Engineering

Background:

• Negative thermal expansion (NTE) is rare in nature, with ice being a prime example.
• Previous research on NTE structures primarily focused on theoretical designs and 2D geometries.
• There is a need for experimentally demonstrated 3D NTE materials.

Purpose of the Study:

• To experimentally fabricate and characterize lightweight multimaterial lattices exhibiting significant 3D NTE.
• To investigate the tunability of NTE properties by altering material composition and geometric design.
• To validate experimental findings with theoretical models and scaling laws.

Main Methods:

• Utilizing multimaterial projection microstereolithography for precise fabrication of complex lattice structures.
• Integrating materials with distinct thermal expansion coefficients to induce structural NTE.
• Conducting experiments to measure thermal expansion over a wide temperature range (170 degrees).

Main Results:

• Successfully fabricated lightweight multimaterial lattices exhibiting significant NTE in three dimensions.
• Demonstrated tunable NTE over a broad range by varying constituent beam properties and lattice geometry.
• Experimental results showed qualitative agreement with a simple scaling law and quantitative agreement with computational models.

Conclusions:

• The study presents a viable method for creating 3D NTE metamaterials through microstereolithography.
• The fabricated lattices offer tunable NTE, opening possibilities for advanced thermal management and functional materials.
• The findings bridge the gap between theoretical NTE designs and experimental realization in 3D structures.