Paper Number
BL29 My Program
Session
Biomaterials, Bio-fluid Dynamics and Biorheology
Title
Microfluidic cell-free layer and yield stress measurements of blood
Presentation Date and Time
October 21, 2025 (Tuesday) 4:25
Track / Room
Track 6 / Sweeney Ballroom C
Authors
- Farrington, Sean M. (University of Delaware, Chemical and Biological Engineering)
- Wagner, Norman (University of Delaware)
- Beris, Antony N. (Univeristy of Delaware, Chemical and Biomolecular Engineering)
Author and Affiliation Lines
Sean M. Farrington, Norman Wagner and Antony N. Beris
Chemical and Biological Engineering, University of Delaware, Newark, DE 19716
Speaker / Presenter
Farrington, Sean M.
Keywords
bio-fluid dynamics; biorheology; colloids; microscopy; non-Newtonian fluids
Text of Abstract
The rheological properties of blood are linked to some cardiovascular diseases, suggesting its use in diagnostic screening. One challenge in implementing blood rheology measurements for diagnostics is the accessibility of the information to physicians. The goal of this research is to create a microfluidic device that measures relevant rheological information. The thixotropic behavior of blood induced by red blood cell aggregates, called rouleaux, is one rheological characteristic of interest to cardiovascular diseases. The yield stress is a key characteristic of thixotropy that is also connected to the rouleaux structure. The rouleaux aggregation occurs at low shear rates; therefore, this study aims to measure low shear rate behaviors of blood in a microfluidic channel to interrogate the thixotropic behavior and yield stress created by rouleaux. An experimental setup was created to control low pressure drops (<100 Pa) with a hydrostatic head in a 1.5 mm wide microfluidic channel to produce low shear rates. Equine red blood cells are resuspended in the polymeric depletant dextran 500 to induce aggregation and phosphate buffered saline to inhibit aggregation. The presence of a 10 μm cell-free layer, significantly larger than the one induced from isolated red blood cells, has been shown in our previous work to be a direct result of rouleaux formation. There the effect of the cell-free layer was studied using rheometry and supported by a two fluid model and initial microfluidic measurements. In this work, additional microfluidic measurements provide further evidence for the cell-free layer. Moreover, observations and quantification of blood’s yield stress were obtained and are consistent with the yield stress inferred from rheometry. This work provides two potential methods for measurement of low shear rate blood rheology parameters that could have clinical diagnostic capabilities in the future.