About

Amir A. Pahlavan is an Assistant Professor of Mechanical Engineering at Yale University, with additional appointments in Materials Science. He holds a Ph.D. from the Massachusetts Institute of Technology, an M.S. from the University of Illinois at Urbana-Champaign, and a B.S. from the University of Tehran. His research focuses on fluid mechanics, soft matter, biophysics, and transport phenomena. Pahlavan has contributed to understanding the evaporation of binary-mixture liquid droplets, microbial dispersion in porous media, particle motion near rough surfaces, and the dynamics of thin films and bubble pinch-off, among other topics. His work involves exploring the stability, dewetting, and contact-line dynamics of thin films, as well as the effects of solid properties on slip at fluid-solid interfaces and the behavior of microorganisms in fluid flows.

Research topics

• Computer Science
• Physics
• Geology
• Materials science
• Environmental science
• Composite material
• Pathology
• Social psychology
• Psychology
• Mathematics
• Geotechnical engineering
• Chemical physics
• Telecommunications
• Statistics
• Mechanics
• Medicine
• Meteorology
• Chemistry

Selected publications

• Solute dispersion enhances the phoretic removal of colloids from dead-end pores

  Journal of Fluid Mechanics · 2026-03-19

  articleOpen accessSenior authorCorresponding

  Predicting and controlling the transport of colloids in porous media is essential for a broad range of applications, from drug delivery to contaminant remediation. Chemical gradients are ubiquitous in these environments, arising from reactions, precipitation/dissolution or salinity contrasts, and can drive particle motion via diffusiophoresis. Yet our current understanding mostly comes from idealised settings with sharply imposed solute gradients, whereas in porous media, flow disorder enhances solute dispersion, and leads to diffuse solute fronts. This raises a central question: Does front dispersion suppress diffusiophoretic migration of colloids in dead-end pores, rendering the effect negligible at larger scales? We address this question using an idealised one-dimensional dead-end geometry. We derive an analytical model for the spatio-temporal evolution of colloids subjected to slowly varying solute fronts and validate it with numerical simulations and microfluidic experiments. Counterintuitively, we find that diffuseness of the solute front enhances removal from dead-end pores: although smoothing reduces instantaneous gradient magnitude, it extends the temporal extent of phoretic forcing, yielding a larger cumulative drift and higher clearance efficiency than sharp fronts. Our results highlight that solute dispersion does not weaken the phoretic migration of colloids from dead-end pores, pointing to the potential relevance of diffusiophoresis at larger scales, with implications for filtration, remediation and targeted delivery in porous media.

  PublisherOA PDFDOI

• Diffusiophoretic transport of colloids in porous media

  Science Advances · 2026-02-11 · 3 citations

  preprintOpen accessSenior author

  Chemical gradients are ubiquitous in porous media flows, from tidal salt gradients in aquifers to irrigation-driven gradients in soils and ionic gradients from metabolic activity in tissues. Although chemical gradients are known to drive diffusiophoretic migration of colloids, these nonequilibrium forces have largely been ignored in porous media flows. Under typical subsurface conditions, flow velocities within preferential pathways exceed phoretic velocities by orders of magnitude, suggesting that diffusiophoresis would be limited to stagnant pockets. Here, using microfluidic experiments, numerical simulations, and theoretical modeling, we show that even moderate solute gradients, typical of natural mixing, can markedly alter colloid transport. We uncover a previously overlooked effect: cross-streamline phoretic migration within preferential flow pathways, which changes macroscopic dispersion by orders of magnitude and suppresses the impact of geometric disorder on transport. Our findings challenge classical models of colloid transport, highlighting the broad implications of solute gradients for technological, biomedical, and environmental applications.

  PublisherDOI

• Interfacial patterns of stretching suspension

  Physical Review Fluids · 2025-10-15

  article

  Understanding particle-mediated interfacial processes in confined spaces undergoing deformation is important for many natural and industrial processes. Here, we combine laboratory experiments and theoretical analysis to investigate how particle dynamics shapes suspension-air interfacial pattern formation when the suspension is stretched. It is found that even slightly nonuniform particle concentration promotes wavy and finger-like morphologies, while particle perturbations lead to dendritic pattern with strong finger branching.

  PublisherDOI

• Diffusioosmotic Reversal of Colloidal Focusing Direction in a Microfluidic T-Junction

  Physical Review Letters · 2025-03-04 · 12 citations

  articleSenior author

  Solute gradients next to an interface drive a diffusioosmotic flow, the origin of which lies in the intermolecular interactions between the solute and the interface. These flows on the surface of colloids introduce an effective slip velocity, driving their diffusiophoretic migration. In confined environments, the interplay between diffusiophoresis and diffusioosmosis governs the motion of colloids. Previous studies have indeed demonstrated the quantitative modulation of phoretic migration by the osmotic flows. Here, we show that diffusioosmotic flows can lead to qualitatively distinct outcomes, reversing the direction of colloidal focusing expected from diffusiophoresis alone. Using microfluidic experiments in a T-junction, numerical simulations, and theoretical modeling, we explain our observations to be due to an interplay between diffusiophoretic migration of colloids toward the walls and their entrainment in a diffusioosmotic vortex. We show this focusing to be persistent for a range of salt types, salt gradients, and flow rates, and establish a criterion for its emergence. Our work sheds light on how boundaries modulate the solute-mediated transport of colloids in confined environments and how the colloidal trajectories can be utilized to infer the surface properties.

  PublisherDOI

• Active Wetting: Statics and Dynamics

  Annual Review of Condensed Matter Physics · 2025-12-19 · 2 citations

  articleOpen access1st authorCorresponding

  Active wetting extends classical wetting physics to living systems, in which cells and tissues spread by generating internal forces rather than relying solely on passive interfacial tensions. Unlike passive systems, which evolve toward thermodynamic and mechanical equilibrium by minimizing free energy, active systems remain far from equilibrium due to continuous energy input and dissipation. Their dynamics are sustained, adaptive, and responsive to chemical and mechanical cues in ways that depart fundamentally from passive behavior. In addition, active systems lack a unified energetic or variational principle to describe their evolution. What insights can be drawn from passive models and how these models might be generalized to account for activity remain open questions. Studying active wetting may thus reveal new principles of nonequilibrium dynamics at soft and living interfaces, and offer deeper understanding of key biological processes such as wound healing, cancer invasion, and biofilm growth.

  PublisherDOI

• Phase-field modeling of two-phase displacement in a capillary tube

  Physical Review Fluids · 2025-08-05 · 5 citations

  article

  Contact lines, where fluid interfaces meet solid surfaces, pose a fundamental challenge to modeling fluid-fluid displacement in confined geometries, as they violate the classical no-slip boundary condition. Recent experiments reveal that contact-line motion in a capillary tube produces compact displacement at low flow rates and unstable fingering at high flow rates. We present a phase-field model with a novel formulation of the boundary wetting conditions. Our model captures the equilibrium configurations at arbitrary wettability, and also predicts dynamic configurations, including wetting transitions, thin-film formation and interface pinch-off, in quantitative agreement with experiments.

  PublisherDOI

• Confinement induces internal flows in adherent cell aggregates

  Journal of The Royal Society Interface · 2024-05-01 · 5 citations

  articleOpen accessCorresponding

  During mesenchymal migration, F-actin protrusion at the leading edge and actomyosin contraction determine the retrograde flow of F-actin within the lamella. The coupling of this flow to integrin-based adhesions determines the force transmitted to the extracellular matrix and the net motion of the cell. In tissues, motion may also arise from convection, driven by gradients in tissue-scale surface tensions and pressures. However, how migration coordinates with convection to determine the net motion of cellular ensembles is unclear. To explore this, we study the spreading of cell aggregates on adhesive micropatterns on compliant substrates. During spreading, a cell monolayer expands from the aggregate towards the adhesive boundary. However, cells are unable to stabilize the protrusion beyond the adhesive boundary, resulting in retraction of the protrusion and detachment of cells from the matrix. Subsequently, the cells move upwards and rearwards, yielding a bulk convective flow towards the centre of the aggregate. The process is cyclic, yielding a steady-state balance between outward (protrusive) migration along the surface, and 'retrograde' (contractile) flows above the surface. Modelling the cell aggregates as confined active droplets, we demonstrate that the interplay between surface tension-driven flows within the aggregate, radially outward monolayer flow and conservation of mass leads to an internal circulation.

  PublisherOA PDFDOI

• soil plastisphere: The nexus of microplastics, bacteria, and biofilms

  InterPore journal. · 2024-11-27 · 7 citations

  articleOpen access1st authorCorresponding

  Bacteria are one of the oldest life forms on Earth, dating back to more than 3.5 billion years ago. They control the global cycling of carbon, nitrogen, and oxygen. They provide plants, fungi and other organisms with the necessary nutrients and elements. They help us digest our food, protect us against pathogens, and even affect our behavior. Microplastics, however, have disrupted the bacterial ecosystems across the globe, from the soil to the oceans. Microplastics are tiny plastic particles formed as a result of the breakdown of the consumer products and plastic waste. Due to their stability and persistence, they can travel long distances in the soil and subsurface environments, ultimately making their way to the water resources, rivers, and oceans. In this journey, they interact with bacteria and other micro/macro-organisms, become ingested or colonized, and act as carriers for contaminants and pathogens. How and whether bacteria adapt to these new microplastic-rich ecosystems are open questions with far-reaching implications for the health of our planet and us. Therefore, there is an urgent need for improving our fundamental understanding of bacterial interactions with the microplastics in complex environments. In this commentary, we focus on the nexus of bacteria, biofilms, and microplastics, also known as the “plastisphere”, and discuss the challenges and opportunities.

  PublisherOA PDFDOI

• Crystal Patterning from Aqueous Solutions via Solutal Instabilities

  ACS Applied Materials & Interfaces · 2024-10-14 · 4 citations

  articleOpen access

  Fluid instabilities can be harnessed for facile self-assembly of patterned structures on the nano- and microscale. Evaporative self-assembly from drops is one simple technique that enables a range of patterning behaviors due to the multitude of fluid instabilities that arise due to the simultaneous existence of temperature and solutal gradients. However, the method suffers from limited controllability over patterns that can arise and their morphology. Here, we demonstrate that a range of distinct crystalline patterns including hexagonal arrays, branches, and sawtooth structures emerge from evaporation of water drops containing calcium sulfate on hydrophilic and superhydrophilic substrates. Different pattern regimes emerge as a function of contact line dynamics and evaporation rates, which dictate which fluid instabilities are most likely to emerge. The underlying physical mechanisms behind instability for controlled self-assembly involve Marangoni flows and forced wetting/dewetting. We also demonstrate that these patterns composed of water-soluble inorganic crystals can serve as sustainable and easily removable masks for applications in microscale fabrication.

  PublisherOA PDFDOI

• Stability Transition in Gap Expansion-Driven Interfacial Flow

  Physical Review Letters · 2024-07-17 · 14 citations

  article

  We investigate interfacial instability in a lifting Hele-Shaw cell by experiments and theory. We characterize the unexplored transition from stable to unstable patterns under a wide range of controlling parameters. Surprisingly, we find that the perturbation growth rate-based criterion for the onset of instability from linear stability theory is too strict by over 3 orders of magnitude. To reconcile this striking discrepancy, we propose a new criterion based on perturbation amplitude, which is in excellent agreement with the experimental results. We further show that the fingering pattern evolves to produce a hierarchical fluid structure and derive a theoretical equation to predict the fingering evolution.

  PublisherDOI

Frequent coauthors

• Rubén Juanes

  Massachusetts Institute of Technology

  47 shared

• Howard A. Stone

  29 shared

• Luis Cueto‐Felgueroso

  Universidad Politécnica de Madrid

  24 shared

• Gareth H. McKinley

  21 shared

• Camille Duprat

  Laboratoire d'Hydrodynamique

  17 shared

• David Saintillan

  13 shared

• Bauyrzhan K. Primkulov

  11 shared

• Benzhong Zhao

  McMaster University

  8 shared

Education

• PhD, Mechanical Engineering

  Massachusetts Institute of Technology

  2018

• M.S., Theoretical and Applied Mechanics

  University of Illinois at Urbana-Champaign

  2010