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Article ; Online: Vibrational manipulation of dry granular materials in lab-on-a-chip devices.

Hui, Timothy C / Zhang, Xiaolin / Adiga, Dhruva / Miller, Gregory H / Ristenpart, William D

2024 Volume 24, Issue 4, Page(s) 966–974

Abstract: We present vibrational techniques to pump, mix, and separate dry granular materials using multifrequency vibrations applied to a solid substrate with a standard audio system. The direction and velocity of the granular flow are tuned by modulating the ... ...

Abstract	We present vibrational techniques to pump, mix, and separate dry granular materials using multifrequency vibrations applied to a solid substrate with a standard audio system. The direction and velocity of the granular flow are tuned by modulating the sign and amplitude, respectively, of the vibratory waveform, with typical pumping velocities of centimeters per second. Different granular materials are mixed by combining them at Y-shaped junctions, and mixtures of granules with different friction coefficients are separated along straight channels by judicious choice of the vibratory waveform. We demonstrate that the observed velocities accord with a theory valid for sufficiently large or fast vibrations, and we discuss the implications for using vibrational manipulation in conjunction with established microfluidic technologies to combine liquid and dry solid handling operations at sub-millimeter length scales.
Language	English
Publishing date	2024-02-13
Publishing country	England
Document type	Journal Article
ZDB-ID	2056646-3
ISSN	1473-0189 ; 1473-0197
ISSN (online)	1473-0189
ISSN	1473-0197
DOI	10.1039/d3lc00722g
Database	MEDical Literature Analysis and Retrieval System OnLINE

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Article ; Online: Controlling the direction of steady electric fields in liquid using nonantiperiodic potentials.

Hashemi, Aref / Tahernia, Mehrdad / Ristenpart, William D / Miller, Gregory H

Physical review. E

2023 Volume 107, Issue 5-1, Page(s) 54608

Abstract: When applying an oscillatory electric potential to an electrolyte solution, it is commonly assumed that the choice of which electrode is grounded or powered does not matter because the time average of the electric potential is zero. Recent theoretical, ... ...

Abstract	When applying an oscillatory electric potential to an electrolyte solution, it is commonly assumed that the choice of which electrode is grounded or powered does not matter because the time average of the electric potential is zero. Recent theoretical, numerical, and experimental work, however, has established that certain types of multimodal oscillatory potentials that are "nonantiperiodic" can induce a net steady field toward either the grounded or powered electrode [A. Hashemi et al., Phys. Rev. E 105, 065001 (2022)2470-004510.1103/PhysRevE.105.065001]. Here, we elaborate on the nature of these steady fields through numerical and theoretical analyses of the asymmetric rectified electric field (AREF). We demonstrate that AREFs induced by a nonantiperiodic electric potential, e.g., by a two-mode waveform with modes at 2 and 3Hz, invariably yields a steady field that is spatially dissymmetric between two parallel electrodes, such that swapping which electrode is powered changes the direction of the field. Furthermore, we show that, while the single-mode AREF occurs in asymmetric electrolytes, nonantiperiodic electric potentials create a steady field in electrolytes even if the cations and anions have the same mobilities. Additionally, using a perturbation expansion, we demonstrate that the dissymmetric AREF occurs due to odd nonlinear orders of the applied potential. We further generalize the theory by demonstrating that the dissymmetric field occurs for all classes of zero-time-average (no dc bias) periodic potentials, including triangular and rectangular pulses, and we discuss how these steady fields can tremendously change the interpretation, design, and applications of electrochemical and electrokinetic systems.
MeSH term(s)	Electricity ; Electrodes ; Electrolytes
Chemical Substances	Electrolytes
Language	English
Publishing date	2023-06-16
Publishing country	United States
Document type	Journal Article
ZDB-ID	2844562-4
ISSN	2470-0053 ; 2470-0045
ISSN (online)	2470-0053
ISSN	2470-0045
DOI	10.1103/PhysRevE.107.054608
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Article ; Online: Net motion induced by nonantiperiodic vibratory or electrophoretic excitations with zero time average.

Hashemi, Aref / Tahernia, Mehrdad / Hui, Timothy C / Ristenpart, William D / Miller, Gregory H

Physical review. E

2022 Volume 105, Issue 6-2, Page(s) 65001

Abstract: It is well established that application of an oscillatory excitation with zero time-average but temporal asymmetry can yield net drift. To date this temporal symmetry breaking and net drift has been explored primarily in the context of point particles, ... ...

Abstract	It is well established that application of an oscillatory excitation with zero time-average but temporal asymmetry can yield net drift. To date this temporal symmetry breaking and net drift has been explored primarily in the context of point particles, nonlinear optics, and quantum systems. Here, we present two new experimental systems where the impact of temporally asymmetric force excitations can be readily observed with mechanical motion of macroscopic objects: (1) solid centimeter-scale objects placed on a uniform flat surface made to vibrate laterally, and (2) charged colloidal particles in water placed between parallel electrodes with an applied oscillatory electric potential. In both cases, net motion is observed both experimentally and numerically with nonantiperiodic, two-mode, sinusoids where the frequency modes are the ratio of odd and even numbers (e.g., 2Hz and 3Hz). The observed direction of motion is always the same for the same applied waveform, and is readily reversed by changing the sign of the applied waveform, for example, by swapping which electrode is powered and grounded. We extend these results to other nonlinear mechanical systems, and we discuss the implications for facile control of object motion using tunable periodic driving forces.
Language	English
Publishing date	2022-07-19
Publishing country	United States
Document type	Journal Article
ZDB-ID	2844562-4
ISSN	2470-0053 ; 2470-0045
ISSN (online)	2470-0053
ISSN	2470-0045
DOI	10.1103/PhysRevE.105.065001
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Book ; Online: Controlling the direction of steady electric fields in liquid using non-antiperiodic potentials

Hashemi, Aref / Tahernia, Mehrdad / Ristenpart, William D. / Miller, Gregory H.

2022

Abstract: When applying an oscillatory electric potential to an electrolyte solution, it is commonly assumed that the choice of which electrode is grounded or powered does not matter because the time-average of the electric potential is zero. Recent theoretical, ... ...

Abstract	When applying an oscillatory electric potential to an electrolyte solution, it is commonly assumed that the choice of which electrode is grounded or powered does not matter because the time-average of the electric potential is zero. Recent theoretical, numerical, and experimental work, however, has established that certain types of multimodal oscillatory potentials that are "non-antiperodic" can induce a net steady field toward either the grounded or powered electrode [Hashemi et al., Phys. Rev. E 105, 065001 (2022)]. Here, we elaborate on the nature of these steady fields through numerical and theoretical analyses of the asymmetric rectified electric field (AREF) that occurs in electrolytes where the cations and anions have different mobilities. We demonstrate that AREFs induced by a non-antiperiodic electric potential, e.g., by a two-mode waveform with modes at 2 and 3 Hz, invariably yields a steady field that is spatially dissymmetric between two parallel electrodes, such that swapping which electrode is powered changes the direction of the field. Additionally, using a perturbation expansion, we demonstrate that the dissymmetric AREF occurs due to odd nonlinear orders of the applied potential. We further generalize the theory by demonstrating that the dissymmetric field occurs for all classes of zero-time-average (no dc bias) periodic potentials, including triangular and rectangular pulses, and we discuss how these steady fields can tremendously change the interpretation, design, and applications of electrochemical and electrokinetic systems.
Keywords	Physics - Applied Physics
Subject code	621
Publishing date	2022-09-22
Publishing country	us
Document type	Book ; Online
Database	BASE - Bielefeld Academic Search Engine (life sciences selection)

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Article ; Online: A perturbation solution to the full Poisson-Nernst-Planck equations yields an asymmetric rectified electric field.

Hashemi, Aref / Miller, Gregory H / Bishop, Kyle J M / Ristenpart, William D

Soft matter

2020 Volume 16, Issue 30, Page(s) 7052–7062

Abstract: We derive a perturbation solution to the one-dimensional Poisson-Nernst-Planck (PNP) equations between parallel electrodes under oscillatory polarization for arbitrary ionic mobilities and valences. Treating the applied potential as the perturbation ... ...

Abstract	We derive a perturbation solution to the one-dimensional Poisson-Nernst-Planck (PNP) equations between parallel electrodes under oscillatory polarization for arbitrary ionic mobilities and valences. Treating the applied potential as the perturbation parameter, we show that the second-order solution yields a nonzero time-average electric field at large distances from the electrodes, corroborating the recent discovery of Asymmetric Rectified Electric Fields (AREFs) via numerical solution to the full nonlinear PNP equations [Hashemi Amrei et al., Phys. Rev. Lett., 2018, 121, 185504]. Importantly, the first-order solution is analytic, while the second-order AREF is semi-analytic and obtained by numerically solving a single linear ordinary differential equation, obviating the need for full numerical solutions to the PNP equations. We demonstrate that at sufficiently high frequencies and electrode spacings the semi-analytical AREF accurately captures both the complicated shape and the magnitude of the AREF, even at large applied potentials.
Language	English
Publishing date	2020-07-10
Publishing country	England
Document type	Journal Article
ZDB-ID	2191476-X
ISSN	1744-6848 ; 1744-683X
ISSN (online)	1744-6848
ISSN	1744-683X
DOI	10.1039/d0sm00417k
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Article ; Online: Asymmetric rectified electric fields between parallel electrodes: Numerical and scaling analyses.

Hashemi Amrei, S M H / Miller, Gregory H / Ristenpart, William D

Physical review. E

2019 Volume 99, Issue 6-1, Page(s) 62603

Abstract: Recent computational and experimental work has established the existence of asymmetric rectified electric fields (AREFs), a type of steady electric field that occurs in liquids in response to an applied oscillatory potential, provided the ions present ... ...

Abstract	Recent computational and experimental work has established the existence of asymmetric rectified electric fields (AREFs), a type of steady electric field that occurs in liquids in response to an applied oscillatory potential, provided the ions present have different mobilities [Hashemi Amrei et al., Phys. Rev. Lett. 121, 185504 (2018)PRLTAO0031-900710.1103/PhysRevLett.121.185504]. Here we use scaling analyses and numerical calculations to elaborate the nature of one-dimensional AREFs between parallel electrodes. The AREF magnitude is shown to increase quadratically with applied potential at low potentials, increase nonlinearly at intermediate potentials, then increase with a constant rate slower than quadratically at sufficiently high potentials, with no impact at any potential on the spatial structure of the AREF. In contrast, the AREF peak location increases linearly with a frequency-dependent diffusive length scale for all conditions tested, with corresponding decreases in both the magnitude and number of sign changes in the directionality of AREF. Furthermore, both the magnitude and spatial structure of the AREF depend sensitively on the ionic mobilities, valencies, and concentrations, with a potential-dependent peak AREF magnitude occurring at an ionic mobility ratio of D_{-}/D_{+}⪅5. The results are summarized with approximate scaling expressions that will facilitate interpretation of the steady component for oscillatory fields in liquid systems.
Language	English
Publishing date	2019-07-22
Publishing country	United States
Document type	Journal Article
ZDB-ID	2844562-4
ISSN	2470-0053 ; 2470-0045
ISSN (online)	2470-0053
ISSN	2470-0045
DOI	10.1103/PhysRevE.99.062603
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Article ; Online: Extreme Levitation of Colloidal Particles in Response to Oscillatory Electric Fields.

Bukosky, Scott C / Hashemi, Aref / Rader, Sean P / Mora, Jeronimo / Miller, Gregory H / Ristenpart, William D

Langmuir : the ACS journal of surfaces and colloids

2019 Volume 35, Issue 21, Page(s) 6971–6980

Abstract: Micron-scale colloidal particles suspended in electrolyte solutions have been shown to exhibit a distinct bifurcation in their average height above the electrode in response to oscillatory electric fields. Recent work by Hashemi Amrei et al. ( Phys. Rev. ...

Abstract	Micron-scale colloidal particles suspended in electrolyte solutions have been shown to exhibit a distinct bifurcation in their average height above the electrode in response to oscillatory electric fields. Recent work by Hashemi Amrei et al. ( Phys. Rev. Lett., 2018, 121, 185504) revealed that a steady, long-range asymmetric rectified electric field (AREF) is formed when an oscillatory potential is applied to an electrolyte with unequal ionic mobilities. In this work, we use confocal microscopy to test the hypothesis that a force balance between gravity and an AREF-induced electrophoretic force is responsible for the particle height bifurcation observed in some electrolytes. We demonstrate that at sufficiently low frequencies, particles suspended in electrolytes with large ionic mobility mismatches exhibit extreme levitation away from the electrode surface (up to 50 particle diameters). This levitation height scales approximately as the inverse square root of the frequency for both NaOH and KOH solutions. Moreover, larger particles levitate smaller distances, while the magnitude of the applied field has little effect above a threshold voltage. A force balance between the AREF-induced electrophoresis and gravity reveals saddle node bifurcations in the levitation height with respect to the frequency, voltage, and particle size, yielding stable fixed points above the electrode that accord with the experimental observations. These results point toward a low-energy, non-fouling method for concentrating colloids at specific locations far from the electrodes.
Language	English
Publishing date	2019-05-16
Publishing country	United States
Document type	Journal Article
ZDB-ID	2005937-1
ISSN	1520-5827 ; 0743-7463
ISSN (online)	1520-5827
ISSN	0743-7463
DOI	10.1021/acs.langmuir.9b00313
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Article ; Online: Oscillating Electric Fields in Liquids Create a Long-Range Steady Field.

Hashemi Amrei, S M H / Bukosky, Scott C / Rader, Sean P / Ristenpart, William D / Miller, Gregory H

Physical review letters

2018 Volume 121, Issue 18, Page(s) 185504

Abstract: We demonstrate that application of an oscillatory electric field to a liquid yields a long-range steady field, provided the ions present have unequal mobilities. The main physics is illustrated by a two-ion harmonic oscillator, yielding an asymmetric ... ...

Abstract	We demonstrate that application of an oscillatory electric field to a liquid yields a long-range steady field, provided the ions present have unequal mobilities. The main physics is illustrated by a two-ion harmonic oscillator, yielding an asymmetric rectified field whose time average scales as the square of the applied field strength. Computations of the fully nonlinear electrokinetic model corroborate the two-ion model and further demonstrate that steady fields extend over large distances between two electrodes. Experimental measurements of the levitation height of micron-scale colloids versus applied frequency accord with the numerical predictions. The heretofore unsuspected existence of a long-range steady field helps explain several long-standing questions regarding the behavior of particles and electrically induced fluid flows in response to oscillatory potentials.
Language	English
Publishing date	2018-11-20
Publishing country	United States
Document type	Journal Article
ZDB-ID	208853-8
ISSN	1079-7114 ; 0031-9007
ISSN (online)	1079-7114
ISSN	0031-9007
DOI	10.1103/PhysRevLett.121.185504
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Article: Mineralogical and transport controls on the evolution of porous media texture using direct numerical simulation

Molins, Sergi / Trebotich, David / Miller, Gregory H. / Steefel, Carl I.

Water resources research. 2017 May, v. 53, no. 5

2017

Abstract: The evolution of porous media due to mineral dissolution and precipitation can change the bulk properties of subsurface materials. The pore‐scale structure of the media, including its physical and mineralogical heterogeneity, exerts controls on porous ... ...

Abstract	The evolution of porous media due to mineral dissolution and precipitation can change the bulk properties of subsurface materials. The pore‐scale structure of the media, including its physical and mineralogical heterogeneity, exerts controls on porous media evolution via transport limitations to reactive surfaces and mineral accessibility. Here we explore how these controls affect the evolution of the texture in porous media at the pore scale. For this purpose, a pore‐scale flow and reactive transport model is developed that explicitly tracks mineral surfaces as they evolve using a direct numerical simulation approach. Simulations of dissolution in single‐mineral domains provide insights into the transport controls at the pore scale, while the simulation of a fracture surface composed of bands of faster‐dissolving calcite and slower‐dissolving dolomite provides insights into the mineralogical controls on evolution. Transport‐limited conditions at the grain‐pack scale may result in unstable evolution, a situation in which dissolution is focused in a fast‐flowing, fast‐dissolving path. Due to increasing velocities, the evolution in these regions is like that observed under conditions closer to strict surface control at the pore scale. That is, grains evolve to have oblong shapes with their long dimensions aligning with the local flow directions. Another example of an evolving reactive transport regime that affects local rates is seen in the evolution of the fracture surface. As calcite dissolves, the diffusive length between the fracture flow path and the receding calcite surfaces increases. Thus, the calcite dissolution reaction becomes increasingly limited by diffusion.
Keywords	calcite ; dolomite ; mathematical models ; research ; texture ; water
Language	English
Dates of publication	2017-05
Size	p. 3645-3661.
Publishing place	John Wiley & Sons, Ltd
Document type	Article
Note	JOURNAL ARTICLE
ZDB-ID	5564-5
ISSN	1944-7973 ; 0043-1397
ISSN (online)	1944-7973
ISSN	0043-1397
DOI	10.1002/2016WR020323
Database	NAL-Catalogue (AGRICOLA)

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Article: Extreme Levitation of Colloidal Particles in Response to Oscillatory Electric Fields

Bukosky, Scott C / Hashemi Amrei, S. M. H / Rader, Sean P / Mora, Jeronimo / Miller, Gregory H / Ristenpart, William D

Langmuir. 2019 May 03, v. 35, no. 21

2019

Abstract	Micron-scale colloidal particles suspended in electrolyte solutions have been shown to exhibit a distinct bifurcation in their average height above the electrode in response to oscillatory electric fields. Recent work by Hashemi Amrei et al. (Phys. Rev. Lett., 2018, 121, 185504) revealed that a steady, long-range asymmetric rectified electric field (AREF) is formed when an oscillatory potential is applied to an electrolyte with unequal ionic mobilities. In this work, we use confocal microscopy to test the hypothesis that a force balance between gravity and an AREF-induced electrophoretic force is responsible for the particle height bifurcation observed in some electrolytes. We demonstrate that at sufficiently low frequencies, particles suspended in electrolytes with large ionic mobility mismatches exhibit extreme levitation away from the electrode surface (up to 50 particle diameters). This levitation height scales approximately as the inverse square root of the frequency for both NaOH and KOH solutions. Moreover, larger particles levitate smaller distances, while the magnitude of the applied field has little effect above a threshold voltage. A force balance between the AREF-induced electrophoresis and gravity reveals saddle node bifurcations in the levitation height with respect to the frequency, voltage, and particle size, yielding stable fixed points above the electrode that accord with the experimental observations. These results point toward a low-energy, non-fouling method for concentrating colloids at specific locations far from the electrodes.
Keywords	colloids ; confocal microscopy ; electric field ; electric potential difference ; electrodes ; electrolytes ; electrophoresis ; gravity ; particle size ; potassium hydroxide ; sodium hydroxide
Language	English
Dates of publication	2019-0503
Size	p. 6971-6980.
Publishing place	American Chemical Society
Document type	Article
ZDB-ID	2005937-1
ISSN	1520-5827 ; 0743-7463
ISSN (online)	1520-5827
ISSN	0743-7463
DOI	10.1021/acs.langmuir.9b00313
Database	NAL-Catalogue (AGRICOLA)

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