A hysteresis-free force curve for highly non-wetting droplets (in ethanol) means more reproducible control of r, since r only depends on the magnitude of applied force F (and hence δ) and not on how F is applied, i.e., path and rate independent. This lack of hysteresis explains the symmetry between the approach and retract curves, i.e., about z = 0.3 µm for r exp and r num in Figure . In contrast, r in air depends not only on the magnitude of the applied force, but also on whether the droplet is approaching or retracting from the surface.