How should the optical tweezers experiment be used to characterize the red blood cell membrane mechanics?

Stretching red blood cells using optical tweezers is a way to characterize the mechanical properties of their membrane by measuring the size of the cell in the direction of the stretching (axial diameter) and perpendicularly (transverse diameter). Recently, such data have been used in numerous publications to validate solvers dedicated to the computation of red blood cell dynamics under flow. In the present study, different mechanical models are used to simulate the stretching of red blood cells by optical tweezers. Results first show that the mechanical moduli of the membranes have to be adjusted as a function of the model used. In addition, by assessing the area dilation of the cells, the axial and transverse diameters measured in optical tweezers experiments are found to be insufficient to discriminate between models relevant to red blood cells or not. At last, it is shown that other quantities such as the height or the profile of the cell should be preferred for validation purposes since they are more sensitive to the membrane model.