Paper Number
CS25                         My Program 

Session
Colloidal Suspensions and Granular Materials

Title
Viscoelasticity of nanocolloidal suspensions from probe rheology: probe size and statistics

Presentation Date and Time
October 21, 2025 (Tuesday) 2:10

Track / Room
Track 1 / Sweeney Ballroom A

Authors (Click on name to view author profile)

1. Pourasgharoshtebin, Masoumeh (Texas Tech University, Department of Chemical Engineering)
2. Furst, Eric M. (University of Delaware, Chemical and Biomolecular Engineering)
3. Khare, Rajesh (Texas Tech University, Department of Chemical Engineering)

Author and Affiliation Lines (in printed abstract book)
Masoumeh Pourasgharoshtebin¹, Eric M. Furst² and Rajesh Khare^1
1Department of Chemical Engineering, Texas Tech University, Lubbock, TX 79409; ²Chemical and Biomolecular Engineering, University of Delaware, Newark, DE 19716

Speaker / Presenter 
Pourasgharoshtebin, Masoumeh

Keywords
computational methods; colloids; suspensions

Text of Abstract
Probe rheology has emerged as a versatile technique for characterizing the viscoelastic properties of soft matter systems at the microscale. Some advantages of probe rheology include its ability to determine local viscoelasticity and hence spatial structural heterogeneities, ability to sample a wide range of frequencies, requirement of a very small amount of sample, and its suitability for measuring the properties of confined systems. These capabilities make it an ideal tool for studying complex fluids under conditions where bulk rheological methods may be inadequate. In previous work [1], we demonstrated the applicability of the probe rheology simulation technique for determining the viscoelastic moduli of a nanocolloidal suspension. A particulate model of colloidal suspension was used in that work and the probe motion was tracked using molecular dynamic simulations. The results showed a dependence of the calculated values on the relative size of the probe compared to the colloidal particles. In this work, we have investigated this effect of probe particle size by studying probes covering a wide size range from a probe particles that is much larger than the size of the colloidal particles at one end, and a probe particle that has the same size as the colloidal particles (lower limit of probe size) at the other end. Probe rheology simulation results are compared with those obtained from oscillatory nonequilibrium molecular dynamics (NEMD) simulations, which are akin to bulk rheological measurements. The employment of smaller probes enables the usage of a larger number of probe particles in the same model system. The effect of the number of probe particles on the accuracy of the results is also investigated in this work. [1] D. Sundaravadivelu Devarajan and R. Khare, J. Rheol. 66, 837–852 (2022).