Non-linear mechanical response of the Red Blood Cell

TL;DR

This study investigates the nonlinear mechanical behavior of human red blood cells, revealing power law stress relaxation and elasticity increase, with implications for understanding their deformation-dependent properties.

Contribution

It demonstrates nonlinear stress relaxation and elasticity in red blood cells, linking experimental observations to the Soft Glassy Rheology Model and bond remodeling mechanisms.

Findings

Stress decays as a power law over time.

Elasticity increases with strain rate following a power law.

Nonlinear response suggests bond breaking during deformation.

Abstract

We measure the dynamical mechanical properties of human red blood cells. Single cell response is measured with optical tweezers. We investigate both the stress relaxation following a fast deformation, and the effect of varying the strain rate. We find a power law decay of the stress as a function of time, down to a plateau stress, and a power law increase of the cell's elasticity as a function of the strain rate. Interestingly, the exponents of these quantities violate the linear superposition principle, indicating a nonlinear response. We propose that this is due to breaking of a fraction of the crosslinks during the deformation process. The Soft Glassy Rheology Model accounts for the relation between the exponents we observe experimentally. This picture is consistent with recent models of bond remodeling in the red blood cell's molecular structure. Our results imply that the blood cell's mechanical behavior depends critically on the deformation process.