Metamaterials with negative compressibility highlight evolving interpretations and opportunities

The idea that a material can exhibit negative compressibility is highly consequential for research and applications. As new forms for this effect are discovered, it is important to examine the range of possible mechanisms and ways to design them into mechanical metamaterials. This comment aims to provide a generalized framework for discussing negative compressibility in materials, especially with the context of metamaterials and open poroelastic systems, going beyond a strict thermodynamic interpretation.