Cell Adhesion to Biomaterials: Concept of Biocompatibility - Advances in Biomaterials Science and Biomedical Applications - page 225

Figure 7. Immersion and emersion loops showing the two types of hysteresis: (A): thermodynamic hysteresis and (B):
kinetic hysteresis. The sample is repeatedly immersed in the liquid leading to typical hysteresis loops. From each loop,
wettability parameters (advancing and receding contact angle or wetting tension) can be calculated

Contact angle hysteresis is often assigned to the surface roughness and heterogeneity.
Actually, a study made by Lam et al. [26], have shown that hysteresis is related to the
molecules' mobility, the liquid diffusion and the surface swelling. These authors had ob‐
served a close dependence between the liquid molecules size and the liquid/material con‐
tact duration. Liquid resorption and retention are the direct causes of hysteresis.
However, as the liquid surface free energy is higher that that of the material; therefore
the liquid retention into the material will increase the material surface free energy and
thus reduces the receding contact angle (θ r ). Indeed, liquids having smaller molecular