Diffusing wave microrheology of strongly attractive dense emulsions

Area of Science:

• Colloid and interface science
• Soft matter physics
• Rheology

Background:

• Microrheology using diffusing wave spectroscopy (DWS) is challenging for attractive emulsions at high volume fractions.
• Collective scattering and probe size effects complicate accurate measurements.

Purpose of the Study:

• To advance the microrheological interpretation of DWS measurements for strongly attractive emulsions.
• To accurately quantify the effective size of DWS probes in dense emulsions.
• To achieve quantitative agreement between microrheological and mechanical rheometry.

Main Methods:

• Applied microrheological analysis to optical diffusing wave spectroscopy (DWS) data.
• Accounted for collective scattering effects in DWS.
• Measured the mean free path of optical transport across various droplet volume fractions (ϕ).
• Utilized a decorated core-shell network model to infer probe size.

Main Results:

• Determined that measuring the optical transport mean free path is crucial for quantifying effective DWS probe size.
• Inferred that DWS probes represent local dense droplet clusters.
• Obtained microrheological elastic shear moduli.
• Demonstrated quantitative agreement between DWS-derived and mechanical rheometry measurements.

Conclusions:

• The refined DWS interpretation accurately characterizes the microrheology of attractive emulsions.
• The decorated core-shell network model effectively describes the probed structures.
• This approach provides a reliable method for determining elastic moduli in dense colloidal systems.