Bulletin of the American Physical Society
APS March Meeting 2024
Monday–Friday, March 4–8, 2024; Minneapolis & Virtual
Session N40: DFD V
11:30 AM–2:18 PM,
Wednesday, March 6, 2024
Room: 103F
Sponsoring
Unit:
DFD
Chair: Arnold Mathijssen, University of Pennsylvania
Abstract: N40.00005 : Electro Drop Friction Force Instrument*
12:18 PM–12:30 PM
Presenter:
Chirag Hinduja
(Max Planck Institute for Polymer Research)
Author:
Chirag Hinduja
(Max Planck Institute for Polymer Research)
Using in-house developed Electro-Drop Friction Force Instrument (eDoFFI), we realized measurements at low capillary numbers (Ca ≤ 10-4). At low capillary numbers, viscous dissipation becomes negligible. The eDoFFI setup facilitates both drop friction and charge measurements simultaneously. For a 5 µL water drop sliding at 2mm/s over 40mm distance, we measure ≈ 3nC of charge on Trichloro(1H,1H,2H,2H-perfluorooctyl) silane (PFOTS) coated glass surface, and ≈ 1 nC on Trichloro Octyl Silane (OTS) coated glass surface. The measured charge does not depend on the drop speed (at mm/s). Next, we measure drop friction on 1 mm thick fused quartz, 1 mm thick glass, and 0.25 mm silicon wafer to investigate the influence of charge separation on drop friction. All the substrates are coated with PFOTS. The lowest friction ≈ 35µN is measured on silicon wafer followed by ≈ 50µN on glass, and ≈ 65µN on fused quartz. Hence, the drop friction is influenced by the substrate’s relative permittivity. Similar dependence of force on substrate’s permittivity is observed even when the charges are not extracted from the drop.
(1) Yatsuzuka, K.; et al., K. Electrification phenomena of pure water droplets dripping and sliding on a polymer surface. Journal of electrostatics 1994, 32 (2), 157-171.
(2) Li, X.; et al. Spontaneous charging affects the motion of sliding drops. Nat. Phys. 2022.
*This research is funded by German Research Society via CRC 1194 (Project C07N & ID 265191195) "Interaction between Transport and Wetting Processes", and the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (grant no. 883631)
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