Soft Nanofluidic Transport in a Soap Film

Abstract

We investigate experimentally the electrokinetic properties of soft nanofluidic channels that consist in soap films with nanometric thickness, covered with charged surfactants. Both the electric and fluidic responses of the system are measured under an applied voltage drop along the film. The electric field is shown to induce an electro-osmotic hydrodynamic flow in the film. However, in contrast to systems confined between solid surfaces, the soft nature of the nanochannel results furthermore in a thickening of the film. This effect accordingly increases the total electro-osmotic flow rate, which behaves nonlinearly with the applied electric field. This behavior is rationalized in terms of an analogy with a Landau-Levich film withdrawn from a reservoir, with the driving velocity identified here with the electro-osmotic one.

Oscillation of the velvet worm slime jet by passive hydrodynamic instability

“…Tissues were fixed in 10% neutral-buffered formalin, processed with paraffin wax, sectioned at 6 μm and stained with haematoxylin and eosin for histological examination4243. We used optical microscopy (Olympus BX41, Olympus camera E330-ADU1.2x, software Olympus Studio 2) to obtain the geometrical parameters involved in the reservoir and papilla duct, and to analyse the tissue structure at papilla and reservoir level.…”

“…The dried layer of soap42 does not allow PDMS to stick either to the template or to the needle. We have been able to produce micropipes of inner diameters ( d ) from 800 μm down to 300 μm in a reproducible way.…”

Electroosmotic flow measurements in a freely suspended liquid film: Experimhents and numerical simulations

“…The vortices were induced within the film by electrohydrodynamic induction, and the fluid velocity depended on the frequency of the AC voltage and the thickness of the liquid film . In , reverse drainage of a cylindrical soap bubble placed between two platinum plate electrodes was investigated. Foam stability is affected by liquid drainage due to gravity; hence, reversing this effect could be beneficial in increasing the half‐life of foam.…”

“…In this study, electroosmotic flow pumped fluid from the bottom reservoir to the top of the film and the flow rate was found to be nonlinear with the applied electric field. Most importantly, the liquid film was not bound by solid surfaces; hence accommodated additional fluid within the column by film thickening . Recently, another study investigated electrokinetic stabilisation of gravitational drainage in free liquid films .…”

Foam Drainage Control Using Thermocapillary Stress in a Two-Dimensional Microchamber

“…Microfluidics gives access to structures unachievable at the macroscopic scale [8,9] and recent studies show that a major difficulty in manufacturing such discrete materials is to control the foam stabilization [10][11][12], or destabilization [13,14] over time, involving three phenomena : i) drainage due to gravity, ii) diffusion of gas through the liquid films, and iii) coalescence of neighboring bubbles [15]. Although microfluidics has proven to be an efficient technology to generate monodisperse bubbles [16], gravity drainage still affects the organization of large number of these bubbles in vertical 2D or 3D matrices -even at such small scales.…”