Understanding and controlling droplet behavior on hydrophobic surfaces is crucial for various applications, from inkjet printing to coating processes.[1,2] Droplet rebound, while beneficial in some cases, can be problematic in others where adhesion is desired. It is therefore important to understand how the droplet wets a solid surface and how the droplet rebound can be suppressed.

One promising approach to control droplet rebound is the addition of polymer additives. These polymers alter fluid properties during impact, affecting energy dissipation and rebound dynamics. At the molecular level, studies show that even small amounts of linear polymers can suppress rebound on flat hydrophobic surfaces, with mechanisms varying based on polymer-surface interactions.[3,4] However, our understanding is limited to linear polymers on flat surfaces.

The effects of surface roughness and diverse polymer types on rebound suppression remain to be fully explored.

Molecular simulation provides a valuable tool for investigating these complex phenomena in terms of providing a view of the process at the molecular level and allowing for the exploration of a wide parameter space that may be challenging to access experimentally.[5] We employ Multi-body Dissipative Particle Dynamics (MDPD), a mesoscale coarse-graining technique suitable for studying polymer solutions and their interactions with surfaces.

Using MDPD, we systematically investigate how polymer properties (molecular weight, concentration, and architecture) influence droplet behavior upon impact with hydrophobic surfaces. This approach aims to broaden our understanding of rebound suppression mechanisms and guide the design of more effective additive formulations for various applications.

In this internship, you will:

• Learn MDPD simulation fundamentals and implementation
• Gain knowledge of droplet wetting on hydrophobic surfaces
• Conduct simulations of static and dynamic wetting processes with various polymer and surface types
• Analyze droplet behavior and rebound suppression mechanisms through key parameters: Dynamic contact angle (θD ), Spreading factor (β), Contact line velocity (vCL) and Contact line friction coefficient (ξCL ).