Paper Number
RS31 

Session
Techniques and Methods: Rheometry & Spectroscopy/Microscopy

Title
Simultaneous characterization of thermophoresis and fluid properties using multiple particle tracking microrhology

Presentation Date and Time
October 12, 2022 (Wednesday) 4:25

Track / Room
Track 6 / Mayfair

Authors (Click on name to view author profile)

  1. Roffin, Maria C. (Lehigh University, Chemical and Biomolecular Engineering)
  2. Hasanova, Nazrin (Lehigh University, Chemical and Biomolecular Engineering)
  3. Cheng, Xuanhong (Lehigh University, Bioengineering)
  4. Schultz, Kelly M. (Lehigh University, Chemical and Biomolecular Engineering)
  5. Gilchrist, James F. (Lehigh University, Chemical and Biomolecular Engineering)

Author and Affiliation Lines (in printed abstract book)
Maria C. Roffin1, Nazrin Hasanova1, Xuanhong Cheng2, Kelly M. Schultz1 and James F. Gilchrist1
1Chemical and Biomolecular Engineering, Lehigh University, Bethlehem, PA 18015; 2Bioengineering, Lehigh University, Bethlehem, PA 18015

Speaker / Presenter 
Roffin, Maria C.

Keywords
experimental methods; directed systems; microscopy; suspensions

Text of Abstract
Thermophoresis is the migration of particles in a fluid driven by a temperature gradient. The applications of this phenomenon are numerous, especially in biomolecular separation, despite no agreement regarding the underlying physics. In fact, existing literature has conflicting experimental results and descriptions of the fundamental mechanism of thermophoresis. The work presented here develops a process to measure thermophoresis of dispersed fluorescent tracer particles and simultaneously measure the local rheological properties of the continuous phase using multiple particle tracking microrheology (MPT). MPT measures the Brownian motion of probe particles and, using the mean squared displacements, relates it to the rheological properties of the fluid. We characterize the particle motion induced by a unidirectional thermal gradient and, at the same time, measure the independent Brownian fluctuations perpendicular to the thermophoretic motion to measure the rheology. In Newtonian fluids, this technique validates the local temperature profile that drives the thermophoretic motion as correlated by the known temperature dependent viscosity. Rayleigh-Benard recirculation due to the temperature dependent fluid density interferes with measurement of the thermophoretic motion, thus parallel experiments in microgravity on the International Space Station are being designed. Moreover, these techniques will be extended to particle thermophoresis in non-Newtonian fluids. A better understanding of the relationship between thermophoresis and the material properties will allow for optimization of thermophoretic bioseparations. A timely application is the advancement of devices used for the viral diagnostic tools enabling the implementation of the thermophoretic enrichment methods for virus detection.