Fig. 1

Probe calibration illustration. In the linear elastic regime, the probe can be described as a spring with stiffness k. The stiffness depends on geometry (R ₀,R _c ,R _p ) of the probe and the aspiration pressure Δ P and is given by Eq. 1. The force at any time is given by the deformation of the RBC Δ x(t)=x(t)−x ₀, where x ₀ is a reference distance measured when the RBC is not under load. It is effectively measured as the distance between the centre of bead and a particular anchor point on the pipette (marked by blue crosses)—a change in this distance corresponds to the change in length of RBC, Δ x