Isotropic Negative Thermal Expansion Metamaterials.

Area of Science:

• Materials Science
• Metamaterials Engineering

Background:

• Negative thermal expansion (NTE) materials are crucial for advanced applications.
• Natural NTE materials are scarce and often underperform, limiting technological progress.

Purpose of the Study:

• To propose a novel method for creating 2D and 3D negative thermal expansion metamaterials.
• To demonstrate isotropic NTE properties in engineered structures.

Main Methods:

• Designing 2D metamaterials using bimaterial strips and antichiral structures.
• Fabricating 3D metamaterials via multimaterial 3D printing.
• Conducting experimental and simulation analyses to validate NTE properties.

Main Results:

• Achieved isotropic negative thermal expansion in both 2D and 3D metamaterials.
• Demonstrated that NTE coefficients depend on material properties and structural parameters (node radius, ligament length).
• Measured high linear negative thermal expansion coefficients in 3D samples, comparable to state-of-the-art experimental values.

Conclusions:

• Antichiral structures provide an effective route to engineer tunable isotropic NTE metamaterials.
• The proposed method offers a practical and scalable approach for material design.
• Findings pave the way for developing advanced materials with tailored thermal expansion characteristics.