title: Two-Aperture Microfluidic Probes as Flow Dipole: Theory and Applications.
abstract: A microfluidic probe (MFP) is a mobile channel-less microfluidic system under which a fluid is injected from an aperture into an open space, hydrodynamically confined by a surrounding fluid, and entirely re-aspirated into a second aperture. Various MFPs have been developed, and have been used for applications ranging from surface patterning of photoresists to local perfusion of organotypic tissue slices. However, the hydrodynamic and mass transfer properties of the flow under the MFP have not been analyzed, and the flow parameters are adjusted empirically. Here, we present an analytical model describing the key transport properties in MFP operation, including the dimensions of the hydrodynamic flow confinement (HFC) area, diffusion broadening, and shear stress as a function of: (i) probe geometry (ii) aspiration-to-injection flow rate ratio (iii) gap between MFP and substrate and (iv) reagent diffusivity. Analytical results and scaling laws were validated against numerical simulations and experimental results from published data. These results will be useful to guide future MFP design and operation, notably to control the MFP "brush stroke" while preserving shear-sensitive cells and tissues.
authors.affiliation: 1] Institut national de la recherche scientifique (INRS)- Énergie Matériaux Télécommunications (EMT), Université du Québec, 1650 Boulevard Lionel-Boulet, Varennes, J3× 1S2, Québec, Canada [2] Department of Biomedical Engineering, McGill University, Montréal, Quebec, H3A 1A4, Canada.
authors.forename: Mohammadali
authors.initials: M
authors.lastname: Safavieh
authors.affiliation: Division of Engineering, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates.
authors.forename: Mohammad A
authors.initials: MA
authors.lastname: Qasaimeh
authors.affiliation: Department of Mathematics, University of British Columbia, Vancouver, British Columbia, V6T 1Z2, Canada.
authors.forename: Ali
authors.initials: A
authors.lastname: Vakil
authors.affiliation: 1] Department of Biomedical Engineering, McGill University, Montréal, Quebec, H3A 1A4, Canada [2] Department of Neurology and Neurosurgery, McGill University, Montréal, Quebec, H3A 1A4, Canada [3] McGill University and Genome Quebec Innovation Centre, Montreal, Quebec, H3A 1A4, Canada.
authors.forename: David
authors.initials: D
authors.lastname: Juncker
authors.affiliation: 1] Department of Engineering Physics, Polytechnique Montréal, Montreal, Quebec, H3C 3A7, Canada [2] Centre de recherche du Centre hospitalier de l'Université de Montréal, and Institut du cancer de Montréal, Montreal, Quebec, H2L 4M1, Canada.
authors.forename: Thomas
authors.initials: T
authors.lastname: Gervais
mesh_terms: D000465:Algorithms; D046210:Microfluidic Analytical Techniques; D044085:Microfluidics / Q000379:methods*; D008962:Models, Theoretical