Molecular dynamics prediction of nanofluidic contact angle offset by an AFM

This paper investigates the nano-fluidic contact angle measurement by performing molecular dynamics simulations. The contact angle between a nano-water droplet and a platinum surface is important for the design of the porous catalyst layer in low-temperature fuel cells. The measurement can generally be conducted by an atomic force microscope (AFM). However, the interaction force between the water droplet and the probe tip of the microscope may influence the measurement results. This paper employs the molecular dynamics technique to investigate the offset of the contact angle measurement. Calculations are in two sets, one simulated the water molecules clustering on the platinum surface, and the other involved the AFM measurement of the contact angle. The former case presents the original contact angle between the nano-scale water droplet and the platinum surface; the offset of the contact angle measurement due to intrusion of the AFM probe is predictable from the latter case. For engineering purposes, we present a correlation between the offset angle and the AFM measurement locations.