title: Microfluidic breakups of confined droplets against a linear obstacle: The importance of the viscosity contrast.
abstract: Combining experiments and theory, we investigate the break-up dynamics of deformable objects, such as drops and bubbles, against a linear micro-obstacle. Our experiments bring the role of the viscosity contrast Δη between dispersed and continuous phases to light: the evolution of the critical capillary number to break a drop as a function of its size is either nonmonotonic (Δη>0) or monotonic (Δη≤0). In the case of positive viscosity contrasts, experiments and modeling reveal the existence of an unexpected critical object size for which the critical capillary number for breakup is minimum. Using simple physical arguments, we derive a model that well describes observations, provides diagrams mapping the four hydrodynamic regimes identified experimentally, and demonstrates that the critical size originating from confinement solely depends on geometrical parameters of the obstacle.
authors.affiliation: IPR, UMR CNRS 6251, Campus Beaulieu, Université Rennes 1, 35042 Rennes, France.
authors.forename: Louis
authors.initials: L
authors.lastname: Salkin
authors.forename: Laurent
authors.initials: L
authors.lastname: Courbin
authors.forename: Pascal
authors.initials: P
authors.lastname: Panizza
mesh_terms: D003198:Computer Simulation; D017276:Friction; D044085:Microfluidics / Q000379:methods*; D008956:Models, Chemical; D033081:Shear Strength; D012996:Solutions / Q000737:chemistry*; D014783:Viscosity
chemical_list: D012996:Solutions