Schemes for the fragmentation and merging of droplets resting on a solid substrate using a patterned wettability...

Area of Science:

• Fluid Dynamics
• Surface Science
• Computational Physics

Background:

• Controlling droplet dynamics on solid surfaces is crucial for various applications.
• Surface wettability plays a significant role in droplet behavior, including spreading, merging, and breakup.
• Existing methods for manipulating droplet dynamics can be limited in precision and control.

Purpose of the Study:

• To propose and demonstrate a novel methodology for controlling water droplet breakup and joining on solid surfaces.
• To investigate the use of wettability gradients in Y-shaped patterns for droplet manipulation.
• To explore the potential for generating multiple droplets of controlled sizes.

Main Methods:

• Development of a computational scheme based on diffuse interface smoothed particle hydrodynamics (SPH) for simulating droplet dynamics.
• Design of Y-shaped surface patterns with controlled wettability gradients along their arms.
• Simulation of droplet interactions, including pulling forces induced by wettability gradients, leading to breakup and merging.

Main Results:

• Demonstrated the ability to break a single water drop into two droplets of equal or unequal sizes by controlling wettability gradients and branch orientation.
• Showcased the breakup of a drop into three smaller droplets using a four-junction wettability pattern.
• Successfully simulated the merging of two water drops into a single drop at a Y-junction due to contact angle gradients.

Conclusions:

• The proposed methodology effectively controls water droplet breakup and joining on solid surfaces through engineered wettability gradients.
• Y-shaped and multi-junction patterns offer versatile platforms for precise droplet manipulation, including size control and generation of multiple droplets.
• This approach holds promise for applications in microfluidics, lab-on-a-chip devices, and advanced material fabrication.