Switchable Imbibition in Nanoporous Gold

TL;DR

This paper demonstrates reversible control of fluid imbibition in nanoporous gold using electric potential, enabling active manipulation of nano-flow rates with low voltages, and explores the underlying charge and flow dynamics.

Contribution

It introduces a method to actively switch fluid flow in nanoporous gold via electric potential, advancing control over nano-scale fluid dynamics.

Findings

Imbibition can be reversibly switched on and off by electric potential.

Scaling laws for imbibition kinetics are established.

Nanoporous gold functions as an electro-capillary pump and flow sensor.

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 geometry of the porous host, 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, i.e. 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 flow dynamics in the metallic nanopores. Our findings demonstrate that the high electric conductivity along with the pathways for ionic and/or fluid transport render nanoporous elemental gold a versatile, accurately controllable electro-capillary pump and flow sensor for minute amounts of liquids with exceptionally low operating voltages.