Impingement of binary nanodroplets on rough surfaces: a molecular dynamics study.

Area of Science:

• Surface Science
• Fluid Dynamics
• Nanotechnology

Background:

• Hydrophobic textured surfaces offer water repellency for applications like self-cleaning and icing resistance.
• The dynamic behavior of impacting binary droplets on nanoscale rough surfaces remains poorly understood.

Purpose of the Study:

• To investigate the impact dynamics of a binary droplet system on hydrophobic textured surfaces using molecular dynamics simulations.
• To elucidate the mechanisms governing droplet coalescence, spreading, retraction, vibration, and bouncing.
• To analyze the influence of surface texture on droplet impact outcomes.

Main Methods:

• Molecular dynamics (MD) simulations were employed to model the impact of a suspended droplet onto a sessile droplet on a textured surface.
• Simulations were conducted under various impact conditions to capture dynamic evolutions.
• Free energy variations were calculated to understand underlying impact mechanisms.

Main Results:

• Observed dynamic evolutions include coalescence, spreading, retraction, vibration, and bouncing.
• Surface texture significantly affects droplet spreading and retraction dynamics, influencing maximum spreading diameter.
• Surface texture promotes droplet bouncing at low Weber numbers (We) but suppresses it at high We.

Conclusions:

• The study provides insights into the nanoscale dynamics of binary droplet impacts on textured surfaces.
• Surface texture plays a critical role in modulating droplet behavior, with distinct effects on bouncing based on the Weber number.
• Findings contribute to the design of surfaces with tailored wettability and impact response.