About

Sandip Ghosal is an Associate Professor of Mechanical Engineering at Northwestern University, with courtesy appointments in Engineering Sciences and Applied Mathematics. He holds a Ph.D. in Physics from Columbia University and a B.S. in Physics from Presidency College, Calcutta, India. His research focuses on fluid mechanics, micro-scale flows, turbulence, and combustion. Ghosal has made significant contributions to understanding complex fluid behaviors, including ionic transport, electrokinetics, and the hydrodynamics of nanopores. He has been recognized as a Fellow of the American Physical Society and has held prestigious visiting positions at Cambridge University and Stanford University. Ghosal is actively involved in professional service, including chairing the Acrivos dissertation award committee for the American Physical Society and serving on editorial advisory boards. He has also been awarded fellowships from the Leverhulme Trust, NASA, and the Searle Center for Teaching Excellence, among others. In addition to his research, Professor Ghosal teaches Fluid Mechanics and Engineering Mathematics at both graduate and undergraduate levels.

Research topics

• Mathematics
• Materials science
• Physics
• Geometry
• Mechanics
• Chemistry
• Thermodynamics
• Composite material
• Mathematical analysis
• Chromatography
• Optics
• Quantum mechanics

Selected publications

• Distribution and natural history notes on the herpetofauna of Ladakh, India

  TAPROBANICA The Journal of Asian Biodiversity · 2023-05-11 · 1 citations

  articleOpen access

  The Himalayas is the highest and youngest mountain range in the world. It provides unique habitat characteristics and is home to a unique assemblage of flora and fauna. There is very little information on the herpetofauna and their ecology in the trans-Himalayan region of Ladakh. Ladakh, located in an area of rain shadow, is characterized by extreme weather, climate, and terrain and relatively lower species richness. The region’s elevation ranges from 2,700 m to over 7,000 m a.s.l. and the annual precipitation is ~90–110 mm while the temperature ranges from -30 oC in winters to 30 oC in the summers.

  PublisherOA PDFDOI

• Packing a flexible fiber into a cavity

  Physical review. E · 2022 · 1 citations

  Senior authorCorresponding
  • Materials science
  • Optics
  • Geometry

  The insertion of an elastic rod or fiber into a confining cavity is studied. Such an insertion is a feature of a variety of problems, including packing and unpacking of DNA in viral capsids and the insertion of catheters during surgery. We consider a simplified geometry in which the container is a smooth (frictionless) circular cylinder of radius a. The fiber is pushed through a hole in the curved surface of the cylinder and is then assumed to stay in a cross-sectional plane perpendicular to the cylinder axis. A solution is found for the fiber shape in which most of the fiber lies against the curved interior surface of the cylinder, apart from the final end section of the fiber, of length 2.0888a, which crosses the interior of the cylinder before ending at the opposite side, which it meets at an angle 1.15 rad to the normal. The force required to push the fiber into the cylinder is EI/2a^{2}, where E is the fiber's Young's modulus and I its cross-sectional moment of inertia. The shape of the final end section of the fiber is confirmed by experiment.

  PublisherDOI

• Charge Selectivity of an Ionic Transistor

  Langmuir · 2021-04-07 · 1 citations

  articleSenior authorCorresponding

  The charge selective properties of a long planar nanochannel with an embedded finite uniformly charged section in the middle are studied. The probability flux of a single test ion initially confined to the inlet reservoir is determined by integrating the Smoluchowski equation using a previously published series solution for the Debye-Hückel potential in this geometry. The charge selective properties are characterized by a dimensionless quantity that we call the "fractional blockage". We study how the fractional blockage depends on the dimensionless parameters that characterize the charge state and channel geometry. In the limit of strongly overlapped wall Debye layers, analytical expressions for the fractional blockage are presented that are found to be in good agreement with numerically computed values in the appropriate asymptotic regimes. These results may be helpful in the design of nanofluidic devices that have a variety of applications.

  PublisherDOI

• Electrophoresis of tightly fitting spheres along a circular cylinder of finite length

  Journal of Fluid Mechanics · 2021 · 4 citations

  Senior authorCorresponding
  • Physics
  • Mechanics
  • Materials science

  Electrophoresis of a tightly fitting sphere of radius $a$ along the centreline of a liquid-filled circular cylinder of radius $R$ is studied for a gap width $h_0=R-a\ll a$ . We assume a Debye length $\kappa ^{-1}\ll h_0$ , so that surface conductivity is negligible for zeta potentials typically seen in experiments, and the Smoluchowski slip velocity is imposed as a boundary condition at the solid surfaces. The pressure difference between the front and rear of the sphere is determined. If the cylinder has finite length $L$ , this pressure difference causes an additional volumetric flow of liquid along the cylinder, increasing the electrophoretic velocity of the sphere, and an analytic prediction for this increase is found when $L\gg R$ . If $N$ identical, well-spaced spheres are present, the electrophoretic velocity of the spheres increases with $N$ , in agreement with the experiments of Misiunas & Keyser ( Phys. Rev. Lett. , vol. 122, 2019, 214501).

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• Effect of Nonzero Solid Permittivity on the Electrical Repulsion between Charged Surfaces

  Langmuir · 2020-03-05 · 1 citations

  articleSenior authorCorresponding

  The electrical repulsion between two charged solid surfaces separated by an electrolyte is studied as a function of the permittivity ϵs of the solid in the limit in which potentials are small, and the gap between the plane solid surfaces is small compared to the Debye length κ–1 within the electrolyte. The solid surfaces are uniformly charged in a central region |x|< L outside which they are uncharged. When ϵs = 0, ions from the charge cloud between the charged surfaces spill out into regions of length O(κ–1) beyond x = ± L, thereby reducing the pressure between the surfaces from that predicted by Derjaguin–Landau–Verwey–Overbeek theory for infinite, uniformly charged surfaces. When ϵs>0, ions spill out over much larger O(L) regions, thereby reducing still further both the electrical potential between the solid surfaces and the repulsive force between them. However, this reduction becomes smaller as κL becomes large.

  PublisherDOI

• Exclusion-Enrichment Effect in Ionic Transistors

  Langmuir · 2020 · 2 citations

  1st authorCorresponding
  • Chemistry
  • Materials science
  • Physics

  A simple model of a nanofluidic transistor consisting of a uniformly charged central section between a pair of plane parallel walls is considered. The linearized Poisson-Boltzmann equation corresponding to weak surface charge is solved exactly, and the solution is presented as an infinite series. The problem is characterized by three dimensionless parameters, namely the normalized surface charge, the ratio of the channel width to the Debye length, and the length-to-width aspect ratio of the charged section. The first of these parameters is presumed small, but the other two are arbitrary. The dependence of the exclusion-enrichment effect on these three parameters is discussed.

  PublisherDOI

• A numerical study of the selectivity of an isolated cylindrical or conical nanopore to a charged macro-ion

  Biomicrofluidics · 2019-09-01 · 6 citations

  articleOpen accessSenior author

  The selectivity of a single nanopore in a uniformly charged solid membrane to a charged analyte ion is studied using numerical simulation. A continuum model is used where the ions are regarded as point particles and characterized by a continuously varying number density. The problem is described by the coupled equations for the electrostatic potential, ion-transport, and hydrodynamic flow, which are solved under appropriate boundary conditions using a finite volume method. The nanopore geometry is considered conical, the cylindrical pore being a special case where the cone angle is zero. The selectivity is characterized by a dimensionless parameter: the pore selectivity index. Results are presented showing how the pore selectivity index varies with the membrane surface charge and other parameters of the problem. The role of hydrodynamic flow on transport properties is examined and found to be consistent with theoretical results on electroosmotic flow through nanopores.

  PublisherOA PDFDOI

• Solid-state nanopore hydrodynamics and transport

  Biomicrofluidics · 2019-01-01 · 42 citations

  articleOpen access1st authorCorresponding

  The resistive pulse method based on measuring the ion current trace as a biomolecule passing through a nanopore has become an important tool in biotechnology for characterizing molecules. A detailed physical understanding of the translocation process is essential if one is to extract the relevant molecular properties from the current signal. In this Perspective, we review some recent progress in our understanding of hydrodynamic flow and transport through nanometer sized pores. We assume that the problems of interest can be addressed through the use of the continuum version of the equations of hydrodynamic and ion transport. Thus, our discussion is restricted to pores of diameter greater than about ten nanometers: such pores are usually synthetic. We address the fundamental nanopore hydrodynamics and ion transport mechanisms and review the wealth of observed phenomena due to these mechanisms. We also suggest future ionic circuits that can be synthesized from different ionic modules based on these phenomena and their applications.

  PublisherOA PDFDOI

• The effect of the finite size of ions and Debye layer overspill on the screened Coulomb interactions between charged flat plates

  Electrophoresis · 2019-12-19 · 10 citations

  article

  Screened repulsion between uniformly charged plates with an intervening electrolyte is analyzed for strongly overlapped electrical double layers (EDL), accounting for the steric effect of ions and their expulsion from EDL edges into the surrounding solution. As a generalization of a study by Philipse et al. which does not account for these effects, an analytical expression is derived for the repulsion pressure in the limit of infinitely long plates with a zero-field assumption, which agrees closely with the corresponding numerical solution at low inter-plate separations. Our results show an augmented repulsive pressure for finite-sized ions at strong EDL overlaps. For plates with a finite lateral size, we demonstrate a further extended domain of low inter-plate gaps where the repulsion pressure increases with ion size due to a strong interplay between the steric interaction of ions and the EDL overspill phenomenon, considered earlier in a study by Ghosal & Sherwood limited to the linear Debye-Hückel regime (which cannot account for the steric effect of ions). This investigation on a simple model should enhance our understanding of the interaction between charged particles in electrophoresis, nanoscale self-assembly, active particles, and various other electrokinetic systems.

  PublisherDOI

• Band Broadening Theories in Capillary Electrophoresis

  Methods in molecular biology · 2018-11-28 · 6 citations

  article1st authorCorresponding
  PublisherDOI

Recent grants

• Dispersion in Capillary Electrophoresis Due to Sample Induced Modification of the Electroosmotic Flow

  NSF · $200k · 2004–2008

• Mathematical modeling of the voltage driven translocation of polyelectrolytes thr

  NIH · $217k · 2009–2012

• Mathematical modeling of the voltage driven translocation of polyelectrolytes thr

  NIH · $94k · 2009–2013

• NIH Grant R01EB007596

  NIH · $315k · 2011

Frequent coauthors

• J. D. Sherwood

  University of Cambridge

  12 shared

• Karim Benzerara

  Institut de minéralogie, de physique des matériaux et de cosmochimie

  8 shared

• Ulrich F. Keyser

  University of Cambridge

  6 shared

• Klas Andersson

  Haldor Topsoe (Denmark)

  6 shared

• Anders Nilsson

  Stockholm University

  6 shared

• Subhra Datta

  5 shared

• Robert L. Kosut

  SC Solutions (United States)

  4 shared

• Roel P. A. Dullens

  Radboud University Nijmegen

  4 shared

Labs

• Ghosal LabPI

Education

• PhD, Physics

  Columbia University

  1992

Awards & honors

• Fellow of the American Physical Society
• Leverhulme Trust Visiting Professor, Cambridge University (U…
• Visiting Fellow, Clare Hall, Cambridge University (UK)
• NASA ASEE Faculty Fellowship
• Fellow of the Searle Center for Teaching Excellence, Northwe…