ARCHER2 Calendar August 2026

Spontaneous rolling of brine droplets on the PAH-covered hydrate surface

Dr Anh Phan, Chemical and Process Engineeringmical Engineering, University of Surrey

The video demonstrates the spontaneous rolling of brine droplets (NaCl and CaCl₂) on a methane–ethane hydrate surface coated with polycyclic aromatic hydrocarbons (PAHs) in pure toluene, as observed via molecular dynamics (MD) simulations run on ARCHER2.
PAHs, known for their unique π–π stacking, hold promise for advanced applications, underscoring the need for a deeper understanding of their interfacial properties. Using MD, we investigated the wetting behavior of brine droplets on hydrate surfaces in various oil solvents. The results highlight synergistic effects from PAHs and ion-specific interactions. The KCl droplet exhibits a larger contact angle than NaCl and CaCl₂ droplets when the toluene volume fraction is below 0.5, with the rate of increase slowing at higher toluene levels. NaCl and CaCl₂ droplets display similar contact angles across all solvent compositions. Notably, in pure toluene, these droplets exhibit contact angles exceeding 150°, occasionally leading to spontaneous rolling on the PAH-covered surface.

This image was published on the August page of the ARCHER2 2026 printed calendar.