title: Static Magnetowetting of Ferrofluid Drops.
abstract: We report results of a comprehensive study of the wetting properties of sessile drops of ferrofluid water solutions at various concentrations deposited on flat substrates and subjected to the action of permanent magnets of different sizes and strengths. The amplitude and the gradient of the magnetic field experienced by the ferrofluid are changed by varying the magnets and their distance to the surface. Magnetic forces up to 100 times the gravitational one and magnetic gradients up to 1 T/cm are achieved. A rich phenomenology is observed, ranging from flattened drops caused by the magnetic attraction to drops extended normally to the substrate because of the normal traction of the magnetic field. We find that the former effect can be conveniently described in terms of an effective Bond number that compares the effective drop attraction with the capillary force, whereas the drop's vertical elongation is effectively expressed by a dimensionless number S, which compares the pressure jump at the ferrofluid interface because of the magnetization with the capillary pressure.
authors.affiliation: Dipartimento di Fisica e Astronomia G. Galilei, Università di Padova , via Marzolo 8, 35131 Padova, Italy.
authors.forename: Carlo
authors.initials: C
authors.lastname: Rigoni
authors.affiliation: Dipartimento di Fisica e Astronomia G. Galilei, Università di Padova , via Marzolo 8, 35131 Padova, Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Pierno
authors.affiliation: Dipartimento di Fisica e Astronomia G. Galilei, Università di Padova , via Marzolo 8, 35131 Padova, Italy.
authors.forename: Giampaolo
authors.initials: G
authors.lastname: Mistura
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, Laboratoire Physico-chimie des Electrolytes et Nanosystèmes InterfaciauX (PHENIX), UMR 8234 CNRS, 4 Place Jussieu, 75005 Paris, France.
authors.forename: Delphine
authors.initials: D
authors.lastname: Talbot
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, Laboratoire Physico-chimie des Electrolytes et Nanosystèmes InterfaciauX (PHENIX), UMR 8234 CNRS, 4 Place Jussieu, 75005 Paris, France.
authors.forename: René
authors.initials: R
authors.lastname: Massart
authors.affiliation: Laboratoire Matière et Systèmes Complexes (MSC), UMR 7057, CNRS and Université Paris Diderot, 75205 Paris, France.
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Bacri
authors.affiliation: Sorbonne Universités, UPMC Univ Paris 06, Laboratoire Physico-chimie des Electrolytes et Nanosystèmes InterfaciauX (PHENIX), UMR 8234 CNRS, 4 Place Jussieu, 75005 Paris, France.
authors.forename: Ali
authors.initials: A
authors.lastname: Abou-Hassan