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arxiv: 1907.09308 · v1 · pith:AL2O5EDOnew · submitted 2019-07-19 · ❄️ cond-mat.soft · physics.flu-dyn

Quincke rotor dynamics in confinement: rolling and hovering

Gerardo E. Pradillo , Hamid Karani , Petia M. Vlahovska This is my paper

Pith reviewed 2026-05-24 18:47 UTC · model grok-4.3

classification ❄️ cond-mat.soft physics.flu-dyn
keywords Quincke rotationelectrohydrodynamic instabilityparticle confinementrolling motionhovering statedielectric sphereDC electric field
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0 comments X

The pith

Confinement between electrodes raises the electric-field threshold for Quincke rolling above the threshold for hovering rotation.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper shows that a dielectric sphere in a uniform DC electric field exhibits Quincke rotation whose onset depends on how tightly it is confined between the two electrodes. At high fields the sphere first rolls along the bottom electrode but the motion becomes unsteady and periodic; at still higher fields the sphere can instead levitate and rotate while hovering in the gap. The critical field strength required to start rolling is measurably higher than the field needed to start hovering rotation. A reader would care because the same instability governs particle motion in many electrohydrodynamic microfluidic and colloidal systems, so confinement must be treated as a control parameter rather than a minor boundary effect.

Core claim

The onset of Quincke rotation strongly depends on particle confinement and the threshold for rolling is higher compared to rotation in the hovering state; in strong fields the rolling velocity becomes time-periodic rather than steady, while a separate regime allows the sphere to levitate and rotate between the electrodes.

What carries the argument

The Quincke electrohydrodynamic instability, which generates a torque on a dielectric sphere placed in a uniform DC electric field.

If this is right

  • Rolling velocity becomes time-periodic once the applied field exceeds a confinement-dependent threshold.
  • Hovering rotation can be initiated at a lower field strength than rolling under the same electrode spacing.
  • The critical field for the onset of any rotation increases as the particle is more tightly confined between the electrodes.
  • Two distinct steady or periodic states (rolling on the electrode versus hovering in the gap) coexist above the hovering threshold.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • Designers of electrohydrodynamic particle transporters could use electrode spacing to select between surface-bound and bulk transport modes.
  • The same confinement dependence may appear in other Quincke-driven systems such as liquid droplets or non-spherical particles.
  • Unsteady rolling might transition to chaotic trajectories at still higher fields, offering a route to controlled mixing in microchannels.

Load-bearing premise

The unsteady rolling and hovering states are produced solely by the Quincke instability and are not dominated by gravity, surface forces, or field inhomogeneities.

What would settle it

Repeating the experiments while systematically varying electrode gap and particle density shows that the measured onset fields for rolling and hovering remain identical regardless of confinement.

Figures

Figures reproduced from arXiv: 1907.09308 by Gerardo E. Pradillo, Hamid Karani, Petia M. Vlahovska.

Figure 1
Figure 1. Figure 1: FIG. 1 [PITH_FULL_IMAGE:figures/full_fig_p001_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: FIG. 2 [PITH_FULL_IMAGE:figures/full_fig_p002_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: FIG. 3 [PITH_FULL_IMAGE:figures/full_fig_p003_3.png] view at source ↗
Figure 5
Figure 5. Figure 5: FIG. 5 [PITH_FULL_IMAGE:figures/full_fig_p004_5.png] view at source ↗
Figure 7
Figure 7. Figure 7: shows that, in general, the threshold for rolling increases with fluid conductivity as expected from the behavior at unconfined electrorotation Eq.(1). How￾ever, unlike the unconfined rotation, there is no unique relation between the threshold field and the conductiv￾ity of the suspending fluid, as highlighted by the shaded regions on [PITH_FULL_IMAGE:figures/full_fig_p004_7.png] view at source ↗
Figure 9
Figure 9. Figure 9: FIG. 9 [PITH_FULL_IMAGE:figures/full_fig_p005_9.png] view at source ↗
Figure 10
Figure 10. Figure 10: FIG. 10 [PITH_FULL_IMAGE:figures/full_fig_p006_10.png] view at source ↗
Figure 11
Figure 11. Figure 11: FIG. 11 [PITH_FULL_IMAGE:figures/full_fig_p006_11.png] view at source ↗
read the original abstract

The Quincke effect is an electrohydrodynamic instability which gives rise to a torque on a dielectric particle in a uniform DC electric field. Previous studies reported that a sphere initially resting on the electrode rolls with steady velocity. We experimentally find that in strong fields the rolling becomes unsteady, with time-periodic velocity. Furthermore, we find another regime, where the rotating sphere levitates in the space between the electrodes. Our experimental results show that the onset of Quincke rotation strongly depends on particle confinement and the threshold for rolling is higher compared to rotation in the hovering state.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 1 minor

Summary. The manuscript reports experimental observations of Quincke rotor dynamics for dielectric spheres confined between parallel electrodes under DC electric fields. It identifies a transition to unsteady, time-periodic rolling at strong fields, a separate hovering (levitating) regime, and a confinement-dependent onset of rotation, with the threshold for rolling higher than for hovering.

Significance. If the central claim holds after addressing potential confounding forces, the work provides new experimental data on how geometric confinement alters Quincke instability thresholds, extending prior studies of free or weakly confined rotors and offering a basis for refined electrohydrodynamic models in narrow gaps.

major comments (2)
  1. [Abstract] Abstract and main text: the central claim that the observed difference in onset thresholds (rolling higher than hovering) arises from confinement geometry alone is load-bearing, yet the description provides no indication of auxiliary controls (e.g., particle density variation, surface passivation, or direct field mapping near the electrode) that would isolate the electrohydrodynamic torque from gravity, static friction, van der Waals adhesion, or small field gradients.
  2. [main text (results/discussion)] The weakest assumption—that unsteady rolling and hovering arise solely from the Quincke instability under the tested conditions—is not yet supported by evidence ruling out comparable-magnitude contributions from unaccounted forces near threshold; without such controls the attribution to confinement remains moderate in strength.
minor comments (1)
  1. [Abstract] The abstract would benefit from quantitative values (e.g., specific field strengths or confinement ratios) for the reported thresholds to allow direct comparison with prior work.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for the detailed review and valuable comments on our manuscript. We address each major comment below and outline the revisions we will make to strengthen the manuscript.

read point-by-point responses

  1. Referee: [Abstract] Abstract and main text: the central claim that the observed difference in onset thresholds (rolling higher than hovering) arises from confinement geometry alone is load-bearing, yet the description provides no indication of auxiliary controls (e.g., particle density variation, surface passivation, or direct field mapping near the electrode) that would isolate the electrohydrodynamic torque from gravity, static friction, van der Waals adhesion, or small field gradients.

    Authors: We agree that additional discussion on potential confounding forces would strengthen the manuscript. In our experiments, the electric field is applied using parallel plate electrodes with a uniform field approximation valid for the gap sizes used. Gravity and buoyancy are accounted for in the hovering regime where the sphere levitates at a height where the net force is zero. We will add a new subsection in the discussion to estimate the magnitudes of static friction, van der Waals forces, and possible field non-uniformities near threshold, showing that the electrohydrodynamic torque dominates the onset behavior. This will clarify why the confinement dependence is the primary factor. revision: yes

  2. Referee: [main text (results/discussion)] The weakest assumption—that unsteady rolling and hovering arise solely from the Quincke instability under the tested conditions—is not yet supported by evidence ruling out comparable-magnitude contributions from unaccounted forces near threshold; without such controls the attribution to confinement remains moderate in strength.

    Authors: The unsteady rolling and hovering are observed only above the critical field predicted by Quincke theory, and the time-periodic nature is characteristic of the instability in confined geometries. However, we acknowledge the need for more explicit ruling out of other forces. In the revised manuscript, we will include calculations comparing the Quincke torque to gravitational, frictional, and adhesive forces at the observed thresholds, demonstrating that other contributions are negligible. This addresses the concern and supports the attribution to confinement effects on the Quincke dynamics. revision: yes

Circularity Check

0 steps flagged

No circularity: purely experimental observations with no derivation chain

full rationale

The paper is an experimental report describing observed regimes of Quincke rotation (steady/unsteady rolling, hovering) and measured onset thresholds under confinement. No equations, fitted parameters, predictions, or self-citations are invoked as load-bearing steps in any derivation. The central claims rest on direct experimental measurements of particle motion, which do not reduce to inputs by construction. This is the expected outcome for a purely observational study.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

The work rests on the established Quincke effect as a domain assumption from prior literature; no free parameters, new entities, or ad-hoc axioms are introduced in the abstract.

axioms (1)
  • domain assumption The Quincke effect is an electrohydrodynamic instability which gives rise to a torque on a dielectric particle in a uniform DC electric field.
    Foundational phenomenon assumed from previous studies, invoked to interpret the observed rolling and hovering.

pith-pipeline@v0.9.0 · 5623 in / 1058 out tokens · 19437 ms · 2026-05-24T18:47:58.624814+00:00 · methodology

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Reference graph

Works this paper leans on

48 extracted references · 48 canonical work pages

  1. [1]

    G. Quincke. Ueber rotation em im constanten elec- trischen felde. Ann. Phys. Chem., 59:417–86, 1896

    work page

  2. [2]

    J. R. Melcher and G. I. Taylor. Electrohydrodynamics - a review of role of interfacial shear stress. Annu. Rev. Fluid Mech., 1:111–146, 1969

    work page 1969

  3. [3]

    T. B. Jones. Quincke rotation of spheres. IEEE Trans. Industry Appl., 20:845–849, 1984

    work page 1984

  4. [4]

    I. Turcu. Electric field induced rotation of spheres. J. Phys. A: Math. Gen., 20:3301–3307, 1987

    work page 1987

  5. [5]

    Lemaire and L

    E. Lemaire and L. Lobry. Chaotic behavior in electro- rotation. Physica A, 314(1-4):663–671, November 2002

    work page 2002

  6. [6]

    Peters, L

    F. Peters, L. Lobry, and E. Lemaire. Experimental ob- servation of lorenz chaos in the quincke rotor dynamics. Chaos, 15:013102, 2005

    work page 2005

  7. [7]

    Vlahovska

    Petia M. Vlahovska. Electrohydrodynamics of drops and vesicles. Annu. Rev. Fluid Mech., 51: 305–330, 2019

    work page 2019

  8. [8]

    Das and D

    D. Das and D. Saintillan. Electrohydrodynamic in- teraction of spherical particles under Quincke rotation. Phys. Rev. E, 87(4):043014, APR 29 2013

    work page 2013

  9. [9]

    Dolinsky and T

    Yu. Dolinsky and T. Elperin. Dipole interaction of the Quincke rotating particles. Phys. Rev. E, 85(2, 2):026608, FEB 27 2012

    work page 2012

  10. [10]

    Dommersnes, A

    P. Dommersnes, A. Mikkelsen, and J. O. Fos- sum. Electro-hydrodynamic propulsion of counter- rotating Pickering drops. Eur. Phys. J. -Special Topics, 225(4):699–706, JUL 2016

    work page 2016

  11. [11]

    negative

    A. C¯ ebers. Bistability and “negative” viscosity for a sus- pension of insulating particles in an electric field. Phys. Rev. Lett., 92(3):034501, Jan 2004

    work page 2004

  12. [12]

    Lemaire, L

    E. Lemaire, L. Lobry, and N. Pannacci. Viscosity of an electro-rheological suspension with internal rotations. J. Rheology, 52:769–783, 2008

    work page 2008

  13. [13]

    Huang, M

    H-F. Huang, M. Zahn, and E. Lemaire. Negative elec- trorheological responses of micro-polar fluids in the finite spin viscosity small spin velocity limit. i. couette flow ge- ometries. J. Electrostatics, 69:442–455, 2011

    work page 2011

  14. [14]

    Pannacci, E

    N. Pannacci, E. Lemaire, and L. Lobry. Dc conductiv- ity of a suspension of insulating particles with internal rotation. Eur. Phys. J. E, 28:411–417, 2009

    work page 2009

  15. [15]

    Y. Hu, M. Miksis, and P. M. Vlahovska. Colloidal particle electrorotation in a nonuniform electric field. Phys. Rev. E, 97:013111, 2018

    work page 2018

  16. [16]

    Cebers, E

    A. Cebers, E. Lemaire, and L. Lobry. Electrohydrody- namic instabilities and orientation of dielectric ellipsoids in low-conducting fluids. Phys. Rev. E, 63:016301, 2000

    work page 2000

  17. [17]

    A. Cebers. Dynamics of an elongated magnetic droplet in a rotating field. Phys. Rev. E, 66(6):061402, Dec 2002

    work page 2002

  18. [18]

    Dolinsky and T

    Y. Dolinsky and T. Elperin. Electrorotation of a leaky dielectric spheroid immersed in a viscous fluid. Phys. Rev. E, 80:066607, 2009

    work page 2009

  19. [19]

    Brosseau, G

    Q. Brosseau, G. Hickey, and P. M. Vlahovska. Electrohy- drodynamic quincke rotation of an ellipsoid. Phys. Rev. Fluids, 2:014101, 2017

    work page 2017

  20. [20]

    Active particles powered by quincke rotation in a bulk fluid

    Debasish Das and Eric Lauga. Active particles powered by quincke rotation in a bulk fluid. Phys. Rev. Lett., 122:194503, May 2019

    work page 2019

  21. [21]

    Lailai Zhu and Howard A. Stone. Propulsion driven by self-oscillation via an electrohydrodynamic instability. Phys. Rev. Fluids, 4:061701, Jun 2019

    work page 2019

  22. [22]

    H. Sato, N. Kaji, T. Mochizuki, and Y. H. Mori. Behavior of oblately deformed droplets in an immiscible dielectric liquid under a steady and uniform electric field. Phys. Fluids, 18:127101, 2006

    work page 2006

  23. [23]

    P. F. Salipante and P. M. Vlahovska. Electrohydrody- namics of drops in strong uniform dc electric fields. Phys. Fluids, 22:112110, 2010

    work page 2010

  24. [24]

    P. F. Salipante and P. M. Vlahovska. Electrohydrody- namic rotations of a viscous droplet. Phys. Rev. E, 88:043003, 2013

    work page 2013

  25. [25]

    Ouriemi and P

    M. Ouriemi and P. M. Vlahovska. Electrohydrody- namic deformation and rotation of a particle-coated drop. Langmuir, 31:6298–6305, 2015

    work page 2015

  26. [26]

    P. M. Vlahovska. Electrohydrodynamic instabilities of viscous drops. Phys. Rev. Fluids, 1:060504, 2016

    work page 2016

  27. [27]

    Jakli, B

    A. Jakli, B. Senyuk, G.X. Liao, and O. Lavrentovich. Colloidal micromotor in smectic a liquid crystal driven by dc electric field. Soft Matter, 4:2471–2474, 2008

    work page 2008

  28. [28]

    Lavrentovich

    Oleg D. Lavrentovich. Active colloids in liquid crystals. Current Opinion in Colloid and Interface Sci., 21(SI):97–109, FEB 2016

    work page 2016

  29. [29]

    Bricard, J.-B

    A. Bricard, J.-B. Caussin, N. Desreumaux, O. Dau- chot, and D. Bartolo. Emergence of macroscopic di- rected motion in populations of motile colloids. Nature, 503(7474):95–98, Nov 7 2013. 8

    work page 2013

  30. [30]

    Emergent vortices in populations of colloidal rollers

    Antoine Bricard, Jean-Baptiste Caussin, Debasish Das, Charles Savoie, Vijayakumar Chikkadi, Kyohei Shitara, Oleksandr Chepizhko, Fernando Peruani, David Saintil- lan, and Denis Bartolo. Emergent vortices in populations of colloidal rollers. Nature Comm., 6:7470, JUN 2015

    work page 2015

  31. [31]

    Belovs and A

    M. Belovs and A. Cebers. Relaxation of polar or- der in suspensions with Quincke effect. Phys. Rev. E, 89(5):052310, MAY 20 2014

    work page 2014

  32. [32]

    Pair aligning improved motility of Quincke rollers

    Shi Qing Lu, Bing Yue Zhang, Zhi Chao Zhang, Yan Shi, and Tian Hui Zhang. Pair aligning improved motility of Quincke rollers. Soft Matter, 14(24):5092–5097, JUN 28 2018

    work page 2018

  33. [33]

    Sounds and hydrodynamics of polar active fluids

    Delphine Geyer, Alexandre Morin, and Denis Bar- tolo. Sounds and hydrodynamics of polar active fluids. Nature Materials, 17(9):789–793, SEP 2018

    work page 2018

  34. [34]

    Distortion and destruc- tion of colloidal flocks in disordered environments

    Alexandre Morin, Nicolas Desreumaux, Jean-Baptiste Caussin, and Denis Bartolo. Distortion and destruc- tion of colloidal flocks in disordered environments. Nature Physics, 13(1):63–67, JAN 2017

    work page 2017

  35. [35]

    Diffusion, subdiffusion, and localization of active colloids in random post lattices

    Alexandre Morin, David Lopes Cardozo, Vijayakumar Chikkadi, and Denis Bartolo. Diffusion, subdiffusion, and localization of active colloids in random post lattices. Phys. Rev. E, 96(4):042611, OCT 26 2017

    work page 2017

  36. [36]

    Sainis, Jason W

    Sunil K. Sainis, Jason W. Merrill, and Eric R. Dufresne. Electrostatic Interactions of Colloidal Particles at Van- ishing Ionic Strength. Langmuir, 24(23):13334–13347, DEC 2 2008

    work page 2008

  37. [37]

    M. F. Hsu, E. R. Dufresne, and D. A. Weitz. Charge sta- bilization in nonpolar solvents. Langmuir, 21(11):4881– 4887, 2005. PMID: 15896027

    work page 2005

  38. [38]

    Sainis, Vincent Germain, Cecile O

    Sunil K. Sainis, Vincent Germain, Cecile O. Mejean, and Eric R. Dufresne. Electrostatic interactions of colloidal particles in nonpolar solvents: Role of surface chemistry and charge control agents. Langmuir, 24(4):1160–1164, FEB 19 2008

    work page 2008

  39. [39]

    Smith and Julian Eastoe

    Gregory N. Smith and Julian Eastoe. Control- ling colloid charge in nonpolar liquids with surfac- tants. Physical Chemistry Chemical Physics, 15(2):424– 439, 2013

    work page 2013

  40. [40]

    Smith, James E

    Gregory N. Smith, James E. Hallett, and Julian Eastoe. Celebrating Soft Matter’s 10th Anniversary: Influencing the charge of poly(methyl methacrylate) latexes in non- polar solvents. Soft Matter, 11(41):8029–8041, 2015

    work page 2015

  41. [41]

    A. J. Goldman, R. G. Cox, and H. Brenner. Slow viscous motion of a sphere parallel to a plane wall –. Chem. Eng. Sci., 22:637–651, 1967

    work page 1967

  42. [42]

    T. N. Tombs. Electrostatic force on a moist particle near a ground plane. The Journal of Adhesion, 51(1-4):15–25, 1995

    work page 1995

  43. [43]

    Roles of AOT molecules on the adhesive force between surfaces in cyclohexane with water contamination

    Y Kanda, T Higuchi, and K Higashitani. Roles of AOT molecules on the adhesive force between surfaces in cyclohexane with water contamination. Advanced Powder Technology , 12(4):577–587, 2001

    work page 2001

  44. [44]

    Edmond W. K. Young and Dongqing Li. Dielec- trophoretic force on a sphere near a planar boundary. Langmuir, 21:12037–12046, 2005

    work page 2005

  45. [45]

    Roy, and Prashanta Dutta

    Mohammad Robiul Hossan, Robert Dillon, Ajit K. Roy, and Prashanta Dutta. Modeling and simulation of dielec- trophoretic particle?particle interactions and assembly. J. Coll. Int. Sci., 394:619–629, 2013

    work page 2013

  46. [46]

    T. N. Tombs and T. B. Jones. Effect of moisture on the dielectrophoretic spectra of glass spheres. IEEE Transactions on Industry Applications, 29(2):281–285, March 1993

    work page 1993

  47. [47]

    J. W. Swan and J. F. Brady. Simulation of hydrody- namically interacting particles near a no-slip boundary. Physics of Fluids, 19:113306, 2007

    work page 2007

  48. [48]

    Unstable fronts and motile structures formed by micro- rollers

    Michelle Driscoll, Blaise Delmotte, Mena Youssef, Ste- fano Sacanna, Aleksandar Donev, and Paul Chaikin. Unstable fronts and motile structures formed by micro- rollers. Nature Physics, 13(4):375–379, APR 2017

    work page 2017