Interdiffusion of liquids of different viscosities in a microchannel

Dambrine, Julien; Géraud, B.; Salmon, Jean‐Baptiste

doi:10.1088/1367-2630/11/7/075015

Cited by 38 publications

(52 citation statements)

References 25 publications

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“…Using this technique, a monolayer of silane-bearing aniline was formed on the substrate via molecular self-assembly. Chemical deposition of the PAni on the modified microchannel walls was performed by filling the microchannel with freshly prepared 1 M HCl solution containing the oxidant 50 (ammonium peroxydisulfate) and aniline in a molar ratio of 0.25:1. This molar ratio was chosen as it has been previously shown that polymerisation of aniline in these experimental conditions produces nanofibres 48 .…”

Section: Microfluidic Device Functionalisationmentioning

confidence: 99%

“…The regions were identified based on their spatial coordinates and were matched between progressive calibration images on this basis. The average 50 Hue component of each region was taken to represent the colour of the channel and reference patches, which were then used for normalisation, and later to generate a calibration plot. Following this, a similar approach was employed to analyse the pH gradient along the channel in which the pH analysis was localised at every 55 point along the channel.…”

Section: Image Processingmentioning

confidence: 99%

“…The PAni coatings were characterised by Raman spectroscopy as it permits in situ analysis 50 of PAni coating inside the microchannel (see ESI † - Figure S4). Raman spectroscopy showed that PAni is obtained in its half-oxidised emeraldine 65 state 51 .…”

Section: Characterisation Of the Pani Coatingsmentioning

confidence: 99%

“…Using the calibration model derived from the sigmoidal regression analysis, the localised Hue values were mapped to their corresponding pH concentrations and a plot of 50 pH concentration over the length of the channel was derived. To reduce noise, a smoothing algorithm based on the Savitzky-Golay filter 62 was applied to the data set.…”

Section: Gradient Ph Measurementsmentioning

confidence: 99%

“…An alternative approach is to use the inherent optical response of certain polymers like the conducting polymer polyaniline (PAni) 50 rather than a conventional pH-sensitive dye. PAni displays striking changes in the visible/NIR spectrum upon protonmediated doping-dedoping of the polymer backbone, thus offering the possibility of developing optical sensors with extended pH ranges.…”

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Dynamic pH mapping in microfluidic devices by integrating adaptive coatings based on polyaniline with colorimetric imaging techniques

et al. 2013

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In this paper we present a microfluidic device that has integrated pH optical sensing capabilities based on polyaniline. The optical properties of polyaniline coatings change in response to the pH of the solution that is flushed inside the microchannel offering the possibility of monitoring pH in continuous flow over a wide pH range throughout the entire channel length. This work also features an innovative detection 10 system for spatial localisation of chemical pH gradients along microfluidic channels through the use of a low cost optical device. Specifically, the use of a microfluidic channel coated with polyaniline is shown to respond colorimetrically to pH and that effect is detected by the detection system, even when pH gradients are induced within the channel. This study explores the capability of detecting this gradient by means of imaging techniques and the mapping of the camera's response to its corresponding pH after a 15 successful calibration process. The provision of an inherently responsive channel means that changes in the pH of a sample moving through the system can be detected dynamically using digital imaging along the entire channel length in real time, without the need to add reagents to the sample. This approach is generic and can be applied to other chemically responsive coatings immobilised on microchannels. Introduction 20Conventional glass-type electrodes have been widely used for pH measures for many years in both industry and academic areas. However, in terms of specific applications (e.g. in vivo, food industry, or for clinical applications), they posses several disadvantages due to their size constraints, rigidity, and the 25 inflexibility of the glass electrode. In recent years, a wide number of pH sensors have been developed to overcome these limitations, including ion sensitive field-effect transistor (iSFET) pH sensors 1-4 , optical pH sensors based on pH responsive dyes 5-8 , hydrogel film pH sensors 9, 10 , and solid-state metal oxides pH sensors 11-13 . 30 In particular, optical pH sensors present several advantages over the traditional pH electrodes as such their low costs, immunity from electromagnetic field, absence of electric contacts, possibility of reference electrode removal and a high degree of miniaturisation 14 . Optical fiber-based pH sensors have been 35 particularly popular, as the fibre allows the optical signal to be transported over long distances, which can facilitate applications in remote sensing 15 .Usually, these optical pH sensors (or optrodes) employ a dye or an indicator that requires immobilisation onto a solid support 40 material. There are several critical issues related to this approach: firstly, the dye should retain its optical properties after the immobilisation process 16 and secondly, it should not leach into the solution 17. A third issue of practical importance is their inherently narrow dynamic response range which is usually 45 around 3-4 pH-units centred on the dye´s pKa 18 .Therefore, the further improvement of such sensors focuses...

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Section: Microfluidic Device Functionalisationmentioning

confidence: 99%

Section: Image Processingmentioning

confidence: 99%

Section: Characterisation Of the Pani Coatingsmentioning

confidence: 99%

Section: Gradient Ph Measurementsmentioning

confidence: 99%

mentioning

confidence: 99%

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Dynamic pH mapping in microfluidic devices by integrating adaptive coatings based on polyaniline with colorimetric imaging techniques

et al. 2013

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Steady microfluidic measurements of mutual diffusion coefficients of liquid binary mixtures

2017

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We present a microfluidic method leading to accurate measurements of the mutual diffusion coefficient of a liquid binary mixture over the whole solute concentration range in a single experiment. This method fully exploits solvent pervaporation through a poly(dimethylsiloxane) (PDMS) membrane to obtain a steady concentration gradient within a microfluidic channel. Our method is applicable for solutes which cannot permeate through PDMS, and requires the activity and the density over the full concentration range as input parameters. We demonstrate the accuracy of our methodology by measuring the mutual diffusion coefficient of the water (1) 1 glycerol (2) mixture, from measurements of the concentration gradient using Raman confocal spectroscopy and the pervaporation-induced flow using particle tracking velocimetry.The red line shows the theoretical velocity profile at z5h=2, the thick lines are the channel edges, and the dotted lines indicate the y-range of selected trajectories. (b) Corresponding evolutionx vs. t for the trajectories shown in (a). Linear fits (not shown for clarity) yield an estimate of the maximal velocity. [Color figure can be viewed at wileyonlinelibrary.com]

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A study of molecular diffusion across a water/oil interface in a Y–Y shaped microfluidic device

Ciceri

Perera

Stevens

2011

Microfluid Nanofluid

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The diffusion behaviour of Co(II) ion in an aqueous homogeneous system and that of 8-hydroxyquinoline (8HQ) in a heterogeneous liquid-liquid system was measured in a Y-Y shaped microfluidic device. We propose a modified version of a previously published equation for a static system to describe the diffusion behaviour of chemical species in this microfluidic device. Specific adaptations of the original equation to the micro environment are illustrated and discussed. The model proposed successfully fitted the diffusion of Co(II) in a homogeneous system (aqueous solutions) and 8HQ across a water/oil interface. We envisage the application of the proposed equation for the discrimination of the diffusion contribution in solvent extraction kinetic studies.

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Interdiffusion of liquids of different viscosities in a microchannel

Cited by 38 publications

References 25 publications

Dynamic pH mapping in microfluidic devices by integrating adaptive coatings based on polyaniline with colorimetric imaging techniques

Dynamic pH mapping in microfluidic devices by integrating adaptive coatings based on polyaniline with colorimetric imaging techniques

Steady microfluidic measurements of mutual diffusion coefficients of liquid binary mixtures

A study of molecular diffusion across a water/oil interface in a Y–Y shaped microfluidic device

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