Viscoelastic transient of confined Red Blood Cells

TL;DR

This study investigates the viscoelastic transient response of confined red blood cells in microchannels, revealing how flow strength influences their membrane viscosity and elasticity, and clarifying discrepancies in previous measurements.

Contribution

It provides a combined experimental, theoretical, and numerical analysis to estimate red blood cell membrane viscosity and elasticity, resolving conflicting literature reports.

Findings

Transient response depends on flow strength

Estimated membrane viscosity is approximately 10^{-7} N·s/m

Clarifies discrepancies in previous measurements of membrane viscosity

Abstract

The unique ability of a red blood cell to flow through extremely small microcapillaries depends on the viscoelastic properties of its membrane. Here, we study in vitro the response time upon flow startup exhibited by red blood cells confined into microchannels. We show that the characteristic transient time depends on the imposed flow strength, and that such a dependence gives access to both the effective viscosity and the elastic modulus controlling the temporal response of red cells. A simple theoretical analysis of our experimental data, validated by numerical simulations, further allows us to compute an estimate for the two-dimensional membrane viscosity of red blood cells, $\eta_{mem}^{2D}\sim 10^{-7}$ N$\cdot$s$\cdot$m$^{-1}$. By comparing our results with those from previous studies, we discuss and clarify the origin of the discrepancies found in the literature regarding the determination of $\eta_{mem}^{2D}$, and reconcile seemingly conflicting conclusions from previous works.