title: Superconfinement tailors fluid flow at microscales.
abstract: Understanding fluid dynamics under extreme confinement, where device and intrinsic fluid length scales become comparable, is essential to successfully develop the coming generations of fluidic devices. Here we report measurements of advancing fluid fronts in such a regime, which we dub superconfinement. We find that the strong coupling between contact-line friction and geometric confinement gives rise to a new stability regime where the maximum speed for a stable moving front exhibits a distinctive response to changes in the bounding geometry. Unstable fronts develop into drop-emitting jets controlled by thermal fluctuations. Numerical simulations reveal that the dynamics in superconfined systems is dominated by interfacial forces. Henceforth, we present a theory that quantifies our experiments in terms of the relevant interfacial length scale, which in our system is the intrinsic contact-line slip length. Our findings show that length-scale overlap can be used as a new fluid-control mechanism in strongly confined systems.
authors.affiliation: 1] Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, UK [2] Department of Chemistry, Faculty of Science, Universiti Teknologi Malaysia, Johor Bahru, Johor 81310, Malaysia.
authors.forename: Siti Aminah
authors.initials: SA
authors.lastname: Setu
authors.affiliation: Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, UK.
authors.forename: Roel P A
authors.initials: RP
authors.lastname: Dullens
authors.affiliation: Departament d'Estructura i Constituents de la Matèria, Universitat de Barcelona, C. Martí i Franquès 1, Barcelona E-08028, Spain.
authors.forename: Aurora
authors.initials: A
authors.lastname: Hernández-Machado
authors.affiliation: Departament de Física Fonamental, Universitat de Barcelona, C. Martí i Franquès 1, Barcelona E-08028, Spain.
authors.forename: Ignacio
authors.identifier: 0000000261875025
authors.initials: I
authors.lastname: Pagonabarraga
authors.affiliation: Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, UK.
authors.forename: Dirk G A L
authors.initials: DG
authors.lastname: Aarts
authors.affiliation: 1] The Rudolf Peierls Centre for Theoretical Physics, University of Oxford, 1 Keble Road, Oxford OX1 3NP, UK [2] Oxford Centre for Collaborative Applied Mathematics, Mathematical Institute, University of Oxford, Radcliffe Observatory Quarter, Woodstock Road, Oxford OX2 6GG, UK [3] Department of Physics and Electrical Engineering, Northumbria University, Ellison Place, Newcastle upon Tyne NE1 8ST, UK.
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Ledesma-Aguilar