title: Capacitive detection of buried interfaces by a dynamic surface force apparatus.
abstract: We present here a new type of distance sensor mounted on a Surface Force Apparatus (SFA), able to detect the position of a buried interface and therefore the thickness of a thin solid or soft matter film coating the SFA surface(s). This sensor relies on the capacitance created by the two metallized surfaces of the SFA. An harmonic oscillation of these polarized surfaces creates a pico- to femto-amps current indicating their relative position. One of the specificities of this sensor is the relatively weak polarization used for the measurements, minimizing the electrical forces and their impact on other interactions, hydrodynamical and mechanical forces measured by the SFA. This original and simple design is of high interest for studying the viscoelastic properties of thin films, to detect adsorbed liquid layers or slippage at liquid-solid interfaces, or even to study complex fluids such as ionic liquids under polarization. We demonstrate the use of this sensor to study the flow boundary condition of silicon oil on a metal surface, and the elastic modulus of a thin elastomer layer.
authors.affiliation: Institut Lumière Matière, Université Lyon 1, CNRS, F-69622 Villeurbanne, France.
authors.forename: Richard
authors.initials: R
authors.lastname: Villey
authors.forename: Agnès
authors.initials: A
authors.lastname: Piednoir
authors.forename: Preeti
authors.initials: P
authors.lastname: Sharma
authors.forename: Cécile
authors.initials: C
authors.lastname: Cottin-Bizonne
authors.forename: Benjamin
authors.initials: B
authors.lastname: Cross
authors.forename: Magali
authors.initials: M
authors.lastname: Phaner-Goutorbe
authors.forename: Élisabeth
authors.initials: É
authors.lastname: Charlaix