Macroscopic Model for Sessile Droplet Evaporation on a Flat Surface

Area of Science:

• Physics
• Fluid Dynamics
• Surface Science

Background:

• Sessile droplet evaporation is complex, involving phase change, diffusion, advection, and surface forces.
• Existing models often struggle to capture the interplay of these factors, necessitating simpler approaches.

Purpose of the Study:

• To develop a simplified yet comprehensive model for sessile droplet evaporation.
• To investigate the influence of droplet shape relaxation and contact line pinning on evaporation dynamics and lifetime.

Main Methods:

• A novel model combining surface free-energy-based shape relaxation dynamics.
• Incorporation of a diffusive evaporation model and a yield stress-governed contact line pinning mechanism.
• Validation against known droplet evaporation and shape relaxation behaviors.

Main Results:

• The model successfully reproduces droplet shape relaxation and evaporation dynamics.
• Shape relaxation significantly influences the overall droplet lifetime.
• Evaporation time dependence on initial contact angle is modulated by the balance between shape relaxation and pinning.

Conclusions:

• The proposed simplified model offers a powerful tool for understanding sessile droplet evaporation.
• Droplet shape dynamics play a crucial role in determining evaporation rates and total evaporation time.
• Contact line pinning mechanisms critically affect evaporation behavior, especially in conjunction with shape relaxation.