arXiv subjects

Rutvik Lathia

Publications and source records attributed to Rutvik Lathia.

3 recordsLinked to original sources

arXiv2026

Drop Spray Electrification

Charge separation during the breakup of water drop has been recognized since the early studies of waterfall and spray electrification, yet the role of controlled drop fragmentation at structured liquid-repellent surfaces remains unclear. Here we show that water drops impacting superhydrophobic meshes generate charged secondary droplets as liquid penetrates and fragments through the mesh pores. By combining Faraday-cup charge measurements with high-speed imaging, we identify how the charge depends on the Weber number and on the pathway of spray formation. No measurable charge is detected below the penetration threshold. At low Weber numbers, recoil jet formation gives a high charge per unit spray mass, whereas at intermediate Weber numbers both recoil jets and impact-induced jets contribute to charging. At higher Weber numbers, pancake bouncing suppresses recoil jet formation, so charging is dominated by impact induced penetration and the total charge approaches a saturated value. We further show that smaller mesh pores enhance the charge-to-mass ratio and that conductive meshes provide stable charging under repeated impacts by dissipating residual surface charge. These findings provide design principles for superhydrophobic mesh platforms for spray charging and rain-driven energy harvesting.

physics.flu-dyn↗

arXiv2026

Mechanisms in Slide Electrification of Liquid and Frozen Drops on Hydrophobic Surfaces

The microscopic and fundamental origin of slide electrification, where droplets of water move across insulating surfaces accumulating and depositing electrical charges, is still debated. Charge transfer is often attributed to ion transfer at the receding contact line. However, it is still unclear whether ion transfer alone can fully account for the observed charge separation. We examined slide electrification of two polar, self-ionizing liquids (water, formamide) and two non-polar liquids (diiodomethane, bromonaphthalene). By cooling below the melting temperature, we were able to compare this process to tribocharging of the respective frozen components. Despite reduced ion mobility at sub-freezing temperatures, the frozen polar compounds continue to accumulate significant charge. Non-polar liquids exhibit lower charging (<25% of polar liquids) and nearly identical charging behaviour in both their liquid and frozen phases on five different substrates. Since non-polar liquids contain few free ions, these observations indicate an alternative charging mechanism, which could be electron transfer. Our findings suggest that slide electrification operates through at least two mechanisms, with the dominant charge transfer pathway shifting between ions and electron transfer depending on the electronegativity, phase, and temperature.

cond-mat.soft↗

arXiv2022

Suppression of Droplet Breakage by Early Onset of Interfacial Instability

Hypothesis: Interfacial instabilities cause undesirable droplet breakage during impact. Such breakage affects many applications, such as printing, spraying, etc. Particle coating over a droplet can significantly change the impact process and stabilize it against breakage. This work investigates the impact dynamics of particle-coated droplets, which mostly remains unexplored. Experiments: Particle-coated droplets of different mass loading were formed using a volume addition. Then the prepared droplets were impacted on superhydrophobic surfaces, and their dynamics were recorded using a high-speed camera. Findings: We report an intriguing phenomenon where interfacial fingering instability helps suppress breakage in particle-coated droplets. This island of breakage suppression, where the droplet maintains its intactness upon impact, appears within a regime of Weber numbers where droplet breakage is inevitable. The onset of fingering instability in particle-coated droplets is observed at much lower impact energy, around two times less than the bare droplet. The instability is characterized using the rim Bond number. The instability suppresses breakage because of the higher losses associated with the formation of stable fingers. Such instability can also be seen in Leidenfrost surfaces and dust/pollen-covered surfaces, making it useful in many applications related to self-cleaning.

physics.flu-dyn↗