DRoplate cracking leads to unwanted spots, reduced resolution in printing, and environmental pollution. Researchers at the Center for Nanoscience and Engineering at the Indian Institute of Science, Bangalore, studied the breaking of droplets on impact, affecting everyday applications such as printing, spraying and coating.
When we look at glossy magazines with beautiful pictures or brightly painted surfaces, we don’t realize that they are made of millions of tiny drops of printing inks or paints. If these droplets form properly and break up when they hit the surface, the quality of the final product will be affected.
The researchers examined particle-encapsulated droplets and their behavior when impacting superhydrophobic surfaces. They discovered that when droplets hit a surface, they break up, which is useful for applications such as printing or spraying. However, by coating the droplets with small hydrophobic particles, they can be prevented from breaking.
“Coating on particles significantly changes droplet behavior upon impact. By studying how particle coatings on droplets alter the impact process, we can find ways to prevent droplet breakage and improve these applications,” says lead researcher Dr. Prosenjit Sen.
The team aims to understand how these special droplets differ in terms of brittleness compared to normal droplets, thereby shedding light on potential applications and benefits.
Droplet breakage leads to undesirable spots, reduced resolution in printing, and environmental pollution. Researchers at the Center for Nanoscience and Engineering at the Indian Institute of Science, Bangalore, studied the breaking of droplets on impact, affecting everyday applications such as printing, spraying and coating.
(From left: Rutwik Lathia, Chandantaru De Modak, Prosenjit Sen)
“The findings also have wider implications for self-cleaning surfaces, anti-icing methods and the spread of disease, and therefore significant practical benefits,” explains Dr Sen.
The coated droplets resisted breaking even when striking the surface with greater force than normal droplets. The team identified a specific interfacial instability that occurs early on the surface of the coated droplets. Unlike normal droplets, this instability creates “fingers” on the droplets, making them more stable and less likely to break up as they bounce off the surface.
“We also found various physical factors such as rim bond number, surface irregularities and particle jamming that help explain why this instability occurs. The presence of these stabilizing fingers reduces the possibility of droplet pinch-off during rebound, resulting in more stable droplets,” the researchers note.
The study found an intriguing phenomenon involving the induction of interfacial fingering instability that helps suppress the collapse of particle-coated droplets. Unlike normal droplets that tend to break up on impact, this instability acts as a protective mechanism, preventing the droplet from breaking up even at high velocities.
“This is an inverse phenomenon that highlights the remarkable stability provided by the presence of particles on the surface of the droplet,” Dr Sen observes.
The findings also highlight the importance of understanding the dynamics of particle-coated interfaces, which has implications in areas such as bioreactor design, digital microfluidics, self-cleaning technologies, and plant diseases spread by pollen-laden droplets.
Apart from Dr. Prosenjit Sen, the team also included Rutvik Lathia and Chandantaru De Modak. The study is published in the Journal of Colloid and Interface Science. It was conducted with the financial assistance of the Department of Science and Technology and the Ministry of Education, Government of India.
India Science Wire