Project Description

Gilbert (1600) and Rayleigh (1882) discovered that electric fields deform drops into cones and fine jets, which subsequently break into micro/nanodrops, are emitted from these pointed-protrusions. This phenomenon was exploited by Fenn who won the 2002 Nobel Prize for development of electrospray-ionization-mass-spectrometry. Since fields can deform and break/coalesce soft matter, applications exploiting this coupling arise in micro/nanofluidics, analytical chemistry, emulsion science, and problems at the intersection of medicine and engineering.

Previous studies focused on drops deforming along the applied field (prolate drops) and conical tips. Recently, researchers showed that drops can deform in the direction perpendicular to the applied field (oblate drops). As field strength increases, oblate drops exhibit three instabilities: Quincke rotation, dimpling and sphere-to-lenticular drop transition. Dimpled-drops pinch to form tori. Lenticular drops emit microscopic/nanoscopic equatorial sheets. These sheets disintegrate to form micro/nanodrops which has the potential to be a game-changer for forming emulsions. If breakup of sheets can be prevented, streaming can be used to make novel-shaped particles/materials. The proposed project seeks to analyze, via theory, scientific computing and experiments, the underlying instabilities and fluid mechanics of micro- and nanoscale flows associated with oblate drops, and universal scaling laws governing the characteristics of the emulsion drops.

Start Date

May-August (early or late summer) 2022

Postdoc Qualifications

The postdoctoral researcher should have a degree in Chemical Engineering, Mechanical Engineering, Applied/Computational Mathematics, Physics or equivalent. The research requires a deep background in fluid mechanics, free surface flows, electric fields and Maxwell's equations, numerical methods, and mathematical analysis of PDEs. Some knowledge and familiarity with experimental techniques and/or an interest in laboratory work, although not required, would also be desirable.

Co-Advisors

1. Professor Osman Basaran, School of Chemical Engineering, obasaran@purdue.edu
2. Professor Ivan Christov, School of Mechanical Engineering, christov@purdue.edu

External Collaborators

Professor Petia Vlahovska, Engineering Sciences and Applied Mathematics and (by courtesy) Mechanical Engineering, Northwestern University, petia.vlahovska@northwestern.edu

Bibliography

1. Wagoner, B. B., Vlahovska, P. M., Haris, M. T., and Basaran, O. A. 2020 Electric field induced transitions from spherical to discocyte and lens shaped drops. J. Fluid Mech. 904, R4.
2. Collins, R. T., Sambath, K., Harris, M. T., and Basaran, O. A. 2013 Universal scaling laws for the disintegration of electrified drops. PNAS 110, 4905-4910.
3. Collins, R. T., Jones, J. J., Harris, M. T., and Basaran O. A. 2008 Electrohydrodynamic tip streaming and emission of charged drops from liquid cones. Nature Phys. 4, 149-154.
4. Yu, Z. and Christov, I. C. 2021 Tuning a magnetic field to generate spinning ferrofluid droplets with controllable speed via nonlinear periodic interfacial waves. Phys. Rev. E 103, 013103.
5. Vlahovska, P. M. 2019 Electrohydrodynamics of drops and vesicles. Ann. Rev. Fluid Mech. 51, 305-330.