All Outputs (26)

Slender phoretic loops and knots (2024)
Journal Article
Katsamba, P., Butler, M. D., Koens, L., & Montenegro-Johnson, T. D. (2024). Slender phoretic loops and knots. Physical Review Fluids, 9(5), Article 054201. https://doi.org/10.1103/PhysRevFluids.9.054201

We present an asymptotic theory for solving the dynamics of slender autophoretic loops and knots. Our formulation is valid for nonintersecting three-dimensional center lines, with arbitrary chemical patterning and varying (circular) cross-sectional r... Read More about Slender phoretic loops and knots.

Viscous tubular-body theory for plane interfaces (2024)
Journal Article
Koens, L., & Walker, B. J. (2024). Viscous tubular-body theory for plane interfaces. Journal of Fluid Mechanics, 979, Article A38. https://doi.org/10.1017/jfm.2023.1085

Filaments are ubiquitous within the microscopic world, occurring in biological and industrial environments and displaying a varied dynamics. Their wide range of applications has spurred the development of a branch of asymptotics focused on the behavi... Read More about Viscous tubular-body theory for plane interfaces.

The slow viscous flow around a general rectangular doubly-periodic arrays of infinite slender cylinders (2023)
Journal Article
Koens, L., Vernekar, R., Krüger, T., Lisicki, M., & Inglis, D. W. (2023). The slow viscous flow around a general rectangular doubly-periodic arrays of infinite slender cylinders. IMA Journal of Applied Mathematics, 88(6), 869-887. https://doi.org/10.1093/imamat/hxae003

The slow viscous flow through a doubly-periodic array of cylinders does not have an analytical solution. However, as a reduced model for the flow within fibrous porous media and microfluidic arrays, this solution is important for many real-world syst... Read More about The slow viscous flow around a general rectangular doubly-periodic arrays of infinite slender cylinders.

Chemically active filaments: analysis and extensions of slender phoretic theory (2022)
Journal Article
Katsamba, P., Butler, M. D., Koens, L., & Montenegro-Johnson, T. D. (2022). Chemically active filaments: analysis and extensions of slender phoretic theory. Soft matter, 18, 7051-7063. https://doi.org/10.1039/d2sm00942k

Autophoretic microswimmers self-propel via surface interactions with a surrounding solute fuel. Chemically-active filaments are an exciting new microswimmer design that augments traditional autophoretic microswimmers, such as spherical Janus particle... Read More about Chemically active filaments: analysis and extensions of slender phoretic theory.

Tubular-body theory for viscous flows (2022)
Journal Article
Koens, L. (2022). Tubular-body theory for viscous flows. Physical Review Fluids, 7(3), Article 034101. https://doi.org/10.1103/PhysRevFluids.7.034101

Cable-like bodies play a key role in many interdisciplinary systems but are hard to simulate. Asymptotic theories, called slender-body theories, are effective but apply in specific regimes and can be hard to extend beyond leading order. In this lette... Read More about Tubular-body theory for viscous flows.

Jet-driven viscous locomotion of confined thermoresponsive microgels (2022)
Journal Article
Tanasijević, I., Jung, O., Koens, L., Mourran, A., & Lauga, E. (2022). Jet-driven viscous locomotion of confined thermoresponsive microgels. Applied physics letters, 120(10), Article 104101. https://doi.org/10.1063/5.0076244

We consider the dynamics of micro-sized, asymmetrically coated thermoresponsive hydrogel ribbons (microgels) under periodic heating and cooling in the confined space between two planar surfaces. As the result of the temperature changes, the volume an... Read More about Jet-driven viscous locomotion of confined thermoresponsive microgels.

Order and information in the patterns of spinning magnetic micro-disks at the air-water interface (2022)
Journal Article
Wang, W., Gardi, G., Malgaretti, P., Kishore, V., Koens, L., Son, D., …Sitti, M. (2022). Order and information in the patterns of spinning magnetic micro-disks at the air-water interface. Science Advances, 8(2), Article eabk0685. https://doi.org/10.1126/sciadv.abk0685

The application of the Shannon entropy to study the relationship between information and structures has yielded insights into molecular and material systems. However, the difficulty in directly observing and manipulating atoms and molecules hampers t... Read More about Order and information in the patterns of spinning magnetic micro-disks at the air-water interface.

Regularized Stokeslets lines suitable for slender bodies in viscous flow (2021)
Journal Article
Zhao, B., & Koens, L. (2021). Regularized Stokeslets lines suitable for slender bodies in viscous flow. Fluids, 6(9), Article 335. https://doi.org/10.3390/fluids6090335

Slender-body approximations have been successfully used to explain many phenomena in low-Reynolds number fluid mechanics. These approximations typically use a line of singularity solutions to represent flow. These singularities can be difficult to im... Read More about Regularized Stokeslets lines suitable for slender bodies in viscous flow.

Local drag of a slender rod parallel to a plane wall in a viscous fluid (2021)
Journal Article
Koens, L., & Montenegro-Johnson, T. D. (2021). Local drag of a slender rod parallel to a plane wall in a viscous fluid. Physical Review Fluids, 6(6), Article 064101. https://doi.org/10.1103/PhysRevFluids.6.064101

The viscous drag on a slender rod by a wall is important to many biological and industrial systems. This drag critically depends on the separation between the rod and the wall and can be approximated asymptotically in specific regimes, namely far fro... Read More about Local drag of a slender rod parallel to a plane wall in a viscous fluid.

Geometric phase methods with Stokes theorem for a general viscous swimmer (2021)
Journal Article
Koens, L., & Lauga, E. (2021). Geometric phase methods with Stokes theorem for a general viscous swimmer. Journal of Fluid Mechanics, 916, Article A17. https://doi.org/10.1017/jfm.2021.181

The geometric phase techniques for swimming in viscous flows express the net displacement of a swimmer as a path integral of a field in configuration space. This representation can be transformed into an area integral for simple swimmers using the St... Read More about Geometric phase methods with Stokes theorem for a general viscous swimmer.

A note on the Stokes phenomenon in flow under an elastic sheet: Stokes Phenomenon in flow under a sheet (2020)
Journal Article
Lustri, C. J., Koens, L., & Pethiyagoda, R. (2020). A note on the Stokes phenomenon in flow under an elastic sheet: Stokes Phenomenon in flow under a sheet. Philosophical transactions. Series A, Mathematical, physical, and engineering sciences, 378(2179), Article 20190530. https://doi.org/10.1098/rsta.2019.0530

The Stokes phenomenon is a class of asymptotic behaviour that was first discovered by Stokes in his study of the Airy function. It has since been shown that the Stokes phenomenon plays a significant role in the behaviour of surface waves on flows pas... Read More about A note on the Stokes phenomenon in flow under an elastic sheet: Stokes Phenomenon in flow under a sheet.

Generalised geometric swimming for Stokes flow (2019)
Presentation / Conference Contribution
Koens, L., & Lauga, E. (2019). Generalised geometric swimming for Stokes flow. In 72nd Annual Meeting of the APS Division of Fluid Dynamics. Meeting Abstracts

Shapere and Wilczek first demonstrated that the displacement of a microscopic swimmer was related to path integrals over a gauge field. This field is a function of the swimmers configuration and laboratory frame position. For simple 1D swimmers, Stok... Read More about Generalised geometric swimming for Stokes flow.

A Light-Driven Microgel Rotor (2019)
Journal Article
Zhang, H., Koens, L., Lauga, E., Mourran, A., & Möller, M. (2019). A Light-Driven Microgel Rotor. Small, 15(46), Article 1903379. https://doi.org/10.1002/smll.201903379

The current understanding of motility through body shape deformation of micro-organisms and the knowledge of fluid flows at the microscale provides ample examples for mimicry and design of soft microrobots. In this work, a 2D spiral is presented that... Read More about A Light-Driven Microgel Rotor.

Method of regularised stokeslets: Flow analysis and improvement of convergence (2019)
Journal Article
Zhao, B., Lauga, E., & Koens, L. (2019). Method of regularised stokeslets: Flow analysis and improvement of convergence. Physical Review Fluids, 4(8), Article 084104. https://doi.org/10.1103/PhysRevFluids.4.084104

Since their development in 2001, regularised stokeslets have become a popular numerical tool for low-Reynolds number flows since the replacement of a point force by a smoothed blob overcomes many computational difficulties associated with flow singul... Read More about Method of regularised stokeslets: Flow analysis and improvement of convergence.

The near and far of a pair of magnetic capillary disks (2019)
Journal Article
Koens, L., Wang, W., Sitti, M., & Lauga, E. (2019). The near and far of a pair of magnetic capillary disks. Soft matter, 15(7), 1497-1507. https://doi.org/10.1039/c8sm02215a

Control on microscopic scales depends critically on our ability to manipulate interactions with different physical fields. The creation of micro-machines therefore requires us to understand how multiple fields, such as surface capillary or electro-ma... Read More about The near and far of a pair of magnetic capillary disks.

The swimming of a deforming helix (2018)
Journal Article
Koens, L., Zhang, H., Moeller, M., Mourran, A., & Lauga, E. (2018). The swimming of a deforming helix. European Physical Journal E, 41(10), Article 119. https://doi.org/10.1140/epje/i2018-11728-2

Abstract.: Many microorganisms and artificial microswimmers use helical appendages in order to generate locomotion. Though often rotated so as to produce thrust, some species of bacteria such Spiroplasma, Rhodobacter sphaeroides and Spirochetes induc... Read More about The swimming of a deforming helix.

The boundary integral formulation of Stokes flows includes slender-body theory (2018)
Journal Article
Koens, L., & Lauga, E. (2018). The boundary integral formulation of Stokes flows includes slender-body theory. Journal of Fluid Mechanics, 850, Article R1. https://doi.org/10.1017/jfm.2018.483

The incompressible Stokes equations can classically be recast in a boundary integral (BI) representation, which provides a general method to solve low-Reynolds-number problems analytically and computationally. Alternatively, one can solve the Stokes... Read More about The boundary integral formulation of Stokes flows includes slender-body theory.

Microscale flow dynamics of ribbons and sheets (2017)
Journal Article
Montenegro-Johnson, T. D., Koens, L., & Lauga, E. (2017). Microscale flow dynamics of ribbons and sheets. Soft matter, 13(3), 546-553. https://doi.org/10.1039/c6sm02105k

Numerical study of the hydrodynamics of thin sheets and ribbons presents difficulties associated with resolving multiple length scales. To circumvent these difficulties, asymptotic methods have been developed to describe the dynamics of slender fibre... Read More about Microscale flow dynamics of ribbons and sheets.

Analytical solutions to slender-ribbon theory (2017)
Journal Article
Koens, L., & Lauga, E. (2017). Analytical solutions to slender-ribbon theory. Physical Review Fluids, 2(8), Article 084101. https://doi.org/10.1103/PhysRevFluids.2.084101

The low-Reynolds-number hydrodynamics of slender ribbons is accurately captured by slender-ribbon theory, an asymptotic solution to the Stokes equation which assumes that the three length scales characterizing the ribbons are well separated. We show... Read More about Analytical solutions to slender-ribbon theory.

The non-Gaussian tops and tails of diffusing boomerangs (2017)
Journal Article
Koens, L., Lisicki, M., & Lauga, E. (2017). The non-Gaussian tops and tails of diffusing boomerangs. Soft matter, 13(16), 2977-2982. https://doi.org/10.1039/c6sm02649d

Experiments involving the two-dimensional passive diffusion of colloidal boomerangs tracked off their centre of mobility have shown striking non-Gaussian tails in their probability distribution function [Chakrabarty et al., Soft Matter, 2016, 12, 431... Read More about The non-Gaussian tops and tails of diffusing boomerangs.