Contact angle hysteresis at the nanoscale: a molecular dynamics simulation study

In this paper, the contact angle hysteresis (CAH) of nanodroplets on both rigid and flexible substrates with different wettabilities was studied using molecular dynamics (MD) simulations. The critical shear stress (CSS) that determines the motion of the contact line (CL) was investigated. A theoretical correlation between CAH and CSS was proposed. Both CAH and CSS reflect the energy dissipation at the CL of the droplet in response to the exerted force. MD results of CAH are qualitatively consistent with the theoretical model. Simulation results also show that, for the same liquid–solid interactions, CAH on the flexible substrate is larger than that on the rigid substrate. These findings aim to enhance our understanding of the mechanism of the CAH at the nanoscale.