Capillary force-driven particle orientation in rod networks

Area of Science:

• Materials Science
• Soft Matter Physics
• Rheology

Background:

• Anisotropic particles, like rods, exhibit unique network structures and rheological behaviors in capillary suspensions compared to spheres.
• Understanding particle orientation is crucial for predicting bulk properties.

Purpose of the Study:

• To investigate the microstructural and rheological changes in capillary suspensions of glass microrods as a function of secondary liquid volume fraction.
• To correlate particle network characteristics (coordination number, clustering, orientation) with macroscopic rheological properties.

Main Methods:

• Dispersion of glass microrods in capillary suspensions with varying secondary liquid volume fractions.
• Analysis of microstructure using confocal microscopy.
• Rheological property measurements via rheometry and rheoconfocal techniques.
• Quantification of particle networks: coordination number, clustering coefficient, orientation distribution.

Main Results:

• Increased secondary liquid fraction shifted rod networks from point-to-point contacts to side-to-side aligned clusters.
• The average clustering coefficient decreased with increasing coordination number, indicating complex cluster formation.
• Rod networks showed increased sensitivity to deformation; higher side-to-side contact probability correlated with greater viscoplastic fragility.

Conclusions:

• The study reveals a transition in anisotropic particle network structures and rheology with changing liquid content.
• Findings provide a basis for engineering advanced materials with tunable mechanical properties by controlling anisotropic particle interactions in capillary suspensions.