Effect of contact angle hysteresis on breakage of a liquid bridge

In this paper, the importance of considering contact angle hysteresis (CAH) during the process of stretching and breaking a liquid bridge between two solid surfaces is addressed. We clearly show that due to the pinning of contact line at the end of the stretching stage, the contact angle between liquid bridge and surfaces cannot be simply assumed to have a constant value (e.g. receding contact angle, θr). Simulation results for stretching a liquid bridge with and without CAH, showed that the contact line pinning can lead to breakage at a larger surface separation and smaller value of pull-off force (Fp). A systematic study about the effect of CAH and contact line pinning on the value of Fp is provided. It is found that when one of the surfaces has a θr larger than 90∘, Fp decreases with the increase of θr on either surface delimiting the bridge. For the cases where θr of both surfaces are smaller than 90∘, significantly smaller Fp is seen when contact line pinning occurs on both surfaces, as compared to Fp when contact line pinning occurs only on one surface. This smaller Fp is caused by more curved profile and later breakage of liquid bridge.