Compressing a spinodal surface at fixed area: bijels in a centrifuge

Area of Science:

• Materials Science
• Soft Matter Physics
• Colloid Science

Background:

• Bicontinuous interfacially jammed emulsion gels (bijels) are unique materials with two interpenetrating continuous phases, stabilized by solid particles.
• Understanding their mechanical response under stress is crucial for applications and fundamental knowledge.

Purpose of the Study:

• To investigate the mechanical behavior and structural changes of bijels under centrifugal compression.
• To elucidate the role of internal structure and defects, such as air bubbles, in the compression process.

Main Methods:

• Bijels were subjected to centrifugal compression to induce stress.
• Macroscopic yielding and microscopic structural evolution were analyzed.
• The influence of trapped air bubbles on the compression mechanism was examined.

Main Results:

• Bijels exhibit macroscopic yielding at low angular acceleration, with irreversible loss of both continuous phases from the top.
• Microscopically, bijels become anisotropic, with domains aligning perpendicular to the compression direction, hindering further liquid expulsion.
• Trapped air bubbles facilitate compression by forming parallel channels that allow liquid escape.

Conclusions:

• Bijel compression is an irreversible process characterized by macroscopic yielding and microscopic structural anisotropy.
• The development of anisotropy inhibits further liquid expulsion, contrasting with colloidal gel sedimentation.
• Air bubbles play a significant role by creating preferential pathways for liquid escape, aiding the overall compression process.