Bubbles enable volumetric negative compressibility in metastable elastocapillary systems

Area of Science:

• Materials Science
• Soft Matter Physics
• Mechanics of Materials

Background:

• Negative compressibility, where materials expand under compression, is a rare and highly sought-after property for advanced applications.
• Achieving this counterintuitive behavior typically requires destabilizing the equilibrium of constituent materials.
• Existing methods for inducing negative compressibility are limited and often complex.

Purpose of the Study:

• To propose a simple and effective strategy for achieving negative compressibility in materials.
• To demonstrate the broad applicability of this strategy across various scales and material types.
• To explore potential applications in fields requiring tunable material responses.

Main Methods:

• Exploiting capillary forces to precompress elastic materials within hydrophobic flexible cavities.
• Utilizing the reversible formation and dissolution of a bubble as a threshold phenomenon to control precompression.
• Investigating the mechanical response of metastable elastocapillary systems under varying pressures.

Main Results:

• Demonstrated negative compressibility in hydrophobic microporous materials, proteins, and millimeter-sized laminae.
• Showcased the ability of capillary forces and bubble dynamics to induce and control this unique property.
• Confirmed the phenomenon's effectiveness across different length scales.

Conclusions:

• The proposed elastocapillary strategy offers a straightforward route to engineer negative compressibility.
• This approach is versatile and applicable to a wide range of materials, from nanoscale biomolecules to macroscopic structures.
• The findings open avenues for developing novel materials with tunable susceptibilities for applications in sensors, porous materials, and beyond.