title: Low Friction Droplet Transportation on a Substrate with a Selective Leidenfrost Effect.
abstract: An energy saving Leidenfrost levitation method is introduced to transport microdroplets with virtually frictionless contact between the liquid and solid substrate. Through microengineering of the heating units, selective areas of the whole substrate can be electrothermally activated. A droplet can be levitated as a result of the Leidenfrost effect and further transported when the substrate is tilted slightly. Selective electroheating produces a uniform temperature distribution on the heating units within 1 s in response to a triggering voltage. Alongside these experimental observations, finite element simulations were conducted to understand the role of substrate thermal conductivity on the temperature profile of the selectively heated substrate. We also generated phase diagrams to verify the Leidenfrost regime for different substrate materials. Finally, we demonstrated the possibility of controlling low friction high speed droplet transportation (∼65 mm/s) when the substrate is tilted (∼7°) by structurally designing the substrate. This work establishes the basis for an entirely new approach to droplet microfluidics.
authors.affiliation: Microsystems Technology Group, School of Engineering & Computing Sciences, Durham University , Durham DH1 3LE, U.K.
authors.forename: Linzi E
authors.initials: LE
authors.lastname: Dodd
authors.affiliation: Microsystems Technology Group, School of Engineering & Computing Sciences, Durham University , Durham DH1 3LE, U.K.
authors.forename: David
authors.initials: D
authors.lastname: Wood
authors.affiliation: Smart Materials and Surfaces Lab, Faculty of Engineering and Environment, Northumbria University , Newcastle upon Tyne NE1 8ST, U.K.
authors.forename: Nicasio R
authors.initials: NR
authors.lastname: Geraldi
authors.affiliation: Smart Materials and Surfaces Lab, Faculty of Engineering and Environment, Northumbria University , Newcastle upon Tyne NE1 8ST, U.K.
authors.forename: Gary G
authors.initials: GG
authors.lastname: Wells
authors.affiliation: Smart Materials and Surfaces Lab, Faculty of Engineering and Environment, Northumbria University , Newcastle upon Tyne NE1 8ST, U.K.
authors.forename: Glen
authors.initials: G
authors.lastname: McHale
authors.affiliation: Smart Materials and Surfaces Lab, Faculty of Engineering and Environment, Northumbria University , Newcastle upon Tyne NE1 8ST, U.K.
authors.forename: Ben B
authors.initials: BB
authors.lastname: Xu
authors.affiliation: Reece Innovation , Armstrong Works, Scotswood Road, Newcastle upon Tyne NE15 6UX, U.K.
authors.forename: Simone
authors.initials: S
authors.lastname: Stuart-Cole
authors.affiliation: Reece Innovation , Armstrong Works, Scotswood Road, Newcastle upon Tyne NE15 6UX, U.K.
authors.forename: James
authors.initials: J
authors.lastname: Martin
authors.affiliation: School of Science and Technology, Nottingham Trent University , Nottingham NG11 8NS, U.K.
authors.forename: Michael I
authors.initials: MI
authors.lastname: Newton
keywords: Leidenfrost effect; MEMS; droplet transportation; microengineering; selective heating