title: Switchable imbibition in nanoporous gold.
abstract: Spontaneous imbibition enables the elegant propelling of nano-flows because of the dominance of capillarity at small length scales. The imbibition kinetics are, however, solely determined by the static host geometry, the capillarity, and the fluidity of the imbibed liquid. This makes active control particularly challenging. Here we show for aqueous electrolyte imbibition in nanoporous gold that the fluid flow can be reversibly switched on and off through electric potential control of the solid-liquid interfacial tension, that is, we can accelerate the imbibition front, stop it, and have it proceed at will. Simultaneous measurements of the mass flux and the electrical current allow us to document simple scaling laws for the imbibition kinetics, and to explore the charge transport in the metallic nanopores. Our findings demonstrate that the high electric conductivity along with the pathways for fluid/ionic transport render nanoporous gold a versatile, accurately controllable electrocapillary pump and flow sensor for minute amounts of liquids with exceptionally low operating voltages.
authors: 1] Institute of Materials Research, Materials Mechanics, Helmholtz-Zentrum Geesthacht, D-21502 Geesthacht, Germany [2] State Key Laboratory for Turbulence and Complex Systems, Center for Applied Physics and Technology, Department of Mechanics and Engineering Science, College of Engineering, Peking University, Beijing 100871, China.
authors: Yahui
authors: Y
authors: Xue
authors: 1] Institute of Materials Research, Materials Mechanics, Helmholtz-Zentrum Geesthacht, D-21502 Geesthacht, Germany [2] Institute of Materials Physics and Technology, Hamburg University of Technology, D-21073 Hamburg, Germany.
authors: Jürgen
authors: J
authors: Markmann
authors: State Key Laboratory for Turbulence and Complex Systems, Center for Applied Physics and Technology, Department of Mechanics and Engineering Science, College of Engineering, Peking University, Beijing 100871, China.
authors: Huiling
authors: H
authors: Duan
authors: 1] Institute of Materials Research, Materials Mechanics, Helmholtz-Zentrum Geesthacht, D-21502 Geesthacht, Germany [2] Institute of Materials Physics and Technology, Hamburg University of Technology, D-21073 Hamburg, Germany.
authors: Jörg
authors: J
authors: Weissmüller
authors: Institute of Materials Physics and Technology, Hamburg University of Technology, D-21073 Hamburg, Germany.
authors: Patrick
authors: P
authors: Huber