title: Deformation of double emulsions under conditions of flow cytometry hydrodynamic focusing.
abstract: Water-in-oil-in-water (w/o/w) microfluidics double emulsions offer a new route to compartmentalise reagents into isolated aqueous microenvironments while maintaining an aqueous carrier fluid phase; this enables compatibility with commercial flow cytometry systems such as fluorescence-activated cell sorting (FACS). Double emulsion (inner core) deformation under hydrodynamic focusing conditions that mimic the environment double emulsions experience in flow cytometry applications is of particular importance for droplet stability and cell viability. This paper reports on an experimental study of the dynamic deformation of aqueous cores of w/o/w double emulsions under hydrodynamic focusing, with the sheath flow directed at 45° to the sample flow. A number of factors affecting the inner core deformation and recovery were examined. Deformation was found to depend significantly on the core or shell viscosity, the droplet-to-sheath flow velocity ratio, and core and shell sizes. Core deformation was found to depend more on the type of surfactant rather concentration with high molecular weight surfactant exhibiting a negligible effect on deformation whereas low molecular weight surfactant enhancing deformation at low concentrations due to their lateral mobility at the interface.
authors.affiliation: Department of Chemistry, University of Cambridge, Cambridge, CB2 1EW, UK and Chemistry Research Laboratory, University of Oxford, Oxford, OX1 3TA, UK.
authors.forename: Shaohua
authors.initials: S
authors.lastname: Ma
authors.affiliation: Department of Chemistry, University of Cambridge, Cambridge, CB2 1EW, UK and Radboud University Nijmegen, Institute for Molecules and Materials, Heyendaalseweg 135, 6525, AJ Nijmegen, The Netherlands.
authors.forename: Wilhelm T S
authors.initials: WT
authors.lastname: Huck
authors.affiliation: Department of Mechanical Engineering, University College London, London, WC1E 7JE, UK. s.balabani@ucl.ac.uk.
authors.forename: Stavroula
authors.initials: S
authors.lastname: Balabani
mesh_terms: D004655:Emulsions / Q000737:chemistry; D005434:Flow Cytometry; D057446:Hydrodynamics; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation; D008970:Molecular Weight; D010316:Particle Size; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry; D014783:Viscosity
chemical_list: D004655:Emulsions; D013501:Surface-Active Agents