title: Measuring the Coefficient of Friction of a Small Floating Liquid Marble.
abstract: This paper investigates the friction coefficient of a moving liquid marble, a small liquid droplet coated with hydrophobic powder and floating on another liquid surface. A floating marble can easily move across water surface due to the low friction, allowing for the transport of aqueous solutions with minimal energy input. However, the motion of a floating marble has yet to be systematically characterised due to the lack of insight into key parameters such as the coefficient of friction between the floating marble and the carrier liquid. We measured the coefficient of friction of a small floating marble using a novel experimental setup that exploits the non-wetting properties of a liquid marble. A floating liquid marble pair containing a minute amount magnetite particles were immobilised and then released in a controlled manner using permanent magnets. The capillarity-driven motion was analysed to determine the coefficient of friction of the liquid marbles. The "capillary charge" model was used to fit the experimental results. We varied the marble content and carrier liquid to establish a relationship between the friction correction factor and the meniscus angle.
authors.affiliation: Queensland Micro- and Nanotechnology Centre, Griffith University, 170 Kessels Road, 4111 Queensland, Australia.
authors.forename: Chin Hong
authors.initials: CH
authors.lastname: Ooi
authors.affiliation: School of Chemical Engineering, University of Queensland, St Lucia, 4072 Queensland, Australia.
authors.forename: Anh Van
authors.initials: AV
authors.lastname: Nguyen
authors.affiliation: School of Engineering, University of Newcastle, Callaghan, NSW 2308, Australia.
authors.forename: Geoffrey M
authors.initials: GM
authors.lastname: Evans
authors.affiliation: Queensland Micro- and Nanotechnology Centre, Griffith University, 170 Kessels Road, 4111 Queensland, Australia.
authors.forename: Dzung Viet
authors.initials: DV
authors.lastname: Dao
authors.affiliation: Queensland Micro- and Nanotechnology Centre, Griffith University, 170 Kessels Road, 4111 Queensland, Australia.
authors.forename: Nam-Trung
authors.initials: NT
authors.lastname: Nguyen