Diffusiophoresis in the presence of a pH gradient

In this article, we study experimentally and theoretically pH-dependent diffusiophoresis of polystyrene particles using a dead-end pore geometry. In particular, the influence of the isoelectric point (pI) on diffusiophoresis is demonstrated in the absence and presence of wall diffusioosmosis. Throughout the paper, we show with experiments and model calculations how the pH-dependent diffusiophoresis and diffusioosmosis influence the particle motion in dead-end pore configurations, including changes that occur when there is a sign change in the zeta potential near the pI.

Publication: S. Shim, J. K. Nunes, G. Chen and H. A. Stone, "Diffusiophoresis in the presence of a pH gradient" Phys. Rev. Fluids, Special Collection on Interfacial Active Matter. 2022, 7, 11, 110513 https://doi.org/10.1103/PhysRevFluids.7.110513

[THEMATIC REVIEW] DIFFUSIOPHORESIS, DIFFUSIOOSMOSIS, AND MICROFLUIDICS: SURFACE-FLOW-DRIVEN PHENOMENA IN THE PRESENCE OF FLOW

In this review article, I introduce studies that reported diffusiophoresis and diffusioosmosis in microfluidic systems, and highlight fundamental aspects by discussing various elements of the phenomena. Important points are: (i) diffusiophoresis and diffusioosmosis are surface-flow-driven phenomena, (ii) particle motion is relative to the fluid, so understanding fluid behavior is necessary, (iii) surfaces and concentration gradients are ubiquitous, and (iv) an integrated approach for analyzing diffusiophoresis and diffusioosmosis is required for the next step in research.

Publication: S. Shim. "Diffusiophoresis, Diffusioosmosis, and Microfluidics: Surface-Flow-Driven Phenomena in the Presence of Flow" Chem. Rev. 2022, 122, 7, 6986–7009 https://doi.org/10.1021/acs.chemrev.1c00571
Supplementary Video: Link to YouTube version of VideoS1.mp4

SPONSTANEOUS PULSE GENERATION IN CHANNEL FLOW

Onset of a channel flow in the presence of gas-permeable walls can induce gas leakage from the liquid stream to the ambient. We found that the leakage of CO₂ from an aqueous suspension of colloidal particles through PDMS walls can cause diffusiophoretic migration of particles. This is possible because water and PDMS contains small amount of dissolved (and dissociated) CO₂ by being in equilibrium with the atmosphere. We suggest that the mechanism can be applied to studies of colloidal dispersion, charge-dependent separation and protein purification.

Publication: S. Shim and H. A. Stone, “CO₂-leakage-driven diffusiophoresis causes spontaneous accumulation of charged materials in channel flow” Proc. Natl. Acad. Sci. U.S.A. 2020, 117 (42) 25985-25990 https://doi.org/10.1073/pnas.2010011117
Video summary: Spontaneous pulse generation in channel flow

CO₂-driven diffusiophoresis of bacteria

CO₂ dissolution in an aqueous phase can create concentration gradient of H⁺ and HCO₃^- ions. We demonstrate diffusiophoresis of bacterial cells in a Hele-Shaw geometry with circular symmetry. Directional migration of the wild-type V. cholerae and a mutant lacking Flagella shows that the motion is diffusiophoresis, not a CO₂-driven chemotaxis. Diffusiophoresis of S. aureus reduces cell adhesion to a surface, and the exclusion of P. aeruginosa lasts > 11 hr after CO₂ is turned off. Diffusiophoresis of bacteria can prevent surface contamination or infection by reducing the population of the cells approaching an interface.

Publication: S. Shim, S. Khodaparast, C.-Y. Lai, J. Yan, J. T. Ault, B. Rallabandi, O. Shardt and H. A. Stone, “CO₂ -Driven diffusiophoresis for maintaining a bacteria-free surface” Soft Matter 2021, 17, 2568-2576. https://doi.org/10.1039/D0SM02023K
Preprint: S. Shim, S. Khodaparast, C.-Y. Lai, J. Yan, J. T. Ault, B. Rallabandi, O. Shardt and H. A. Stone, "CO₂ -driven diffusiophoresis for removal of bacteria" arXiv:2009.07081 (16 Sep. 2020)

Microfluidics & diffusiophoresis

We utilize a dead-end pore geometry to study electrolyte diffusion and diffusiophoresis of charged particles. Particles in dead-end pores translate and disperse by diffusiophoresis and diffusioosmosis, respectively. For quantitative description of the particle distribution, we must consider three-dimensional flow structure in the rectangular pore. We derive an effective one-dimensional equation, similar to a Taylor dispersion analysis.

Publications:
B. M. Alessio, S. Shim, A. Gupta and H. A. Stone, "Diffusioosmosis-driven dispersion of colloids: a Taylor dispersion analysis with experimental validation" J. Fluid Mech. 2022, 942, A23
B. M. Alessio, S. Shim, E. Mintah, A. Gupta and H. A. Stone, “Diffusiophoresis and diffusioosmosis in tandem: Two-dimensional particle motion in the presence of multiple electrolytes” Phys. Rev. Fluids, 2021, 6, 054201 https://doi.org/10.1103/PhysRevFluids.6.054201
A. Gupta, S. Shim and H. A. Stone, “Diffusiophoresis: from dilute to concentrated electrolytes” Soft Matter, 2020, 16, 6975-6984 https://doi.org/10.1039/D0SM00899K
J. L. Wilson, S. Shim, Y. E. Yu, A. Gupta and H. A. Stone, “Diffusiophoresis in multivalent electrolytes” Langmuir, 2020, 36, 7014-7020 https://doi.org/10.1021/acs.langmuir.9b03333
A. Gupta, S. Shim , L. Issah, C. McKenzie and H. A. Stone, "Diffusion of multiple electrolytes cannot be treated independently: model predictions with experimental validations” Soft Matter, 2019, 15, 9965-9973 https://doi.org/10.1039/C9SM01780A

Damped coalescence cascade of liquid drops

Damped coalescence cascade typically occurs when the surface tension difference between the bath and the drop is larger than a critical value. A local Marangoni flow generated in the bath at every pinch-off accelerates air drainage in the gap between the daughter drop and the bath, and thus leads to suppression of the rebound of the daughter drop.

Publication: S. Shim and H. A. Stone, “Damped coalescence cascade of liquid drops” Phys. Rev. Fluids, 2, 044001 (2017) https://doi.org/10.1103/PhysRevFluids.2.044001

CO₂-driven diffusiophoresis for water cleaning

We investigate diffusiophoretic exclusion of polystyrene particles in a rectangular channel flow, driven by CO₂ dissolution from one side-wall. We model the problem by applying a shear flow approximation in a two-dimensional configuration and using the similarity transform. The definition of the similarity variable suggests a characteristic length scale for the particle exclusion zone.

Publication: S. Shim, M. Baskaran, E. H. Thai, and H. A. Stone, "CO ₂ -Driven diffusiophoresis and water cleaning: similarity solutions for predicting the exclusion zone in a channel flow" Lab Chip 2021, 21, 3387-3400. [https://doi.org/10.1039/D1LC00211B][1]
Preprint: arXiv:2105.15154 (31 May 2021)

Evaporative cooling with thin-film flow of water

We suggest a design where thin-film flow of water can evaporate and decrease the temperature of the system. By creating nanostructures on the surface of aluminum using hydrothermal synthesis, we were able to increase the wettability of the surface and let water form thin film as it flows down. Under a dry condition (RH < 5 %), the model device is cooled by 6 °C within 20 minutes.

S. Shim, Interfacial Flows with Heat and Mass Transfer, Ph.D Thesis, Princeton University, Princeton, NJ (2017)

Dissolution without disappearing: multicomponent dissolution of CO₂ bubbles

CO₂ bubbles that entered a microfluidic channel did not disappear, despite the rapid dissolution of CO₂ in an aqueous phase. This is due to the influx of air into the bubble from the surrounding liquid. We solve for a multicomponent diffusion problem for a spherical bubble, to predict the equilibrium radii under various surfactant concentrations.

Publication: S. Shim, J. Wan, S. Hilgenfeldt, P. Panchal and H. A. Stone, “Dissolution without disappearing: multicomponent gas exchange for CO₂ bubbles in a microfluidic channel” Lab Chip, 2014, 14, 2428-2436 https://doi.org/10.1039/C4LC00354C

More publications:
A. Somasundar, B. Qin, S. Shim, B. Bassler and H. A. Stone, "Diffusiophoretic particle penetration into bacterial biofilms" ACS Applied Materials & Interfaces 2023, 15, 33263−33272 https://doi.org/10.1021/acsami.3c03190
Y. E. Yu, M. Magnini, L. Zhu, S. Shim and H. A. Stone, "Non-unique bubble dynamics in a vertical capillary with an external flow" J. Fluid Mech. 2021, 911, A34 https://doi.org/10.1017/jfm.2020.1027
S. Shim, R. M. Ford and H. A. Stone, "Chemotaxis in shear flow: similarity solutions for chemoattractant concentrations and bacteria distribution" AICHE J. 2019, 65: e16713 https://doi.org/10.1002/aic.16713
Y. E. Yu, L. Zhu, S. Shim, J. Eggers and H. A. Stone, "Time-dependent motion of a confined bubble in a tube: Transition between two steady states" J. Fluid Mech. 2018, 857, R4 https://doi.org/10.1017/jfm.2018.835

Conference Proceedings:
T. Keeley-LeClaire, E. Teitelbaum, S. Shim, M. Bozlar, H. A. Stone and F. M. Meggers, "Extracting radiant cooling from building exhaust air using the Maisotsenko Cycle principle" 7th International Building Physics Conference Syracuse, NY, USA, Sep. 2018
S. Shim, S. Lee and K. H. Kang, "Meniscus vibration at the tip of piezoelectric inkjet nozzle: observation and analysis" 2009 Korean Society of Mechanical Engineers (KSME) Fall's Conference, Yongpyong, S. Korea, Nov. 2009