Nanobubbles and gas dynamics during capillary filling of nanochannels

This paper focuses on capillary filling at the nanoscale where deviations to the Washburn’s classical theory are observed. Imbibition experiments in microfabricated silicon-glass nanochannels with low aspect ratio (width >> depth and depths going from 400 nm down to 20 nm) are performed for several liquids. In all cases, as predicted by the Washburn’s law, liquid invasion front location evolves as the square root of time. However, filling kinetics slowdown compared to the Washburn’s law is measured in nanochannels for depths below ~ 100 nm. Furthermore, below a liquid-dependent depth threshold, we observe spontaneous bubbles formation behind the advancing meniscus. Bubbles dynamics (formation conditions and lifetime) are analyzed thanks to our experimental data involving several liquids and nanochannels depths. Viscous resistance induced by the bubbles presence is estimated using an effective medium approach. Conjointly, gas flow ahead of the advancing meniscus is modeled considering the gas as viscous and compressible. Influence of these effects on the filling kinetics is discussed

Etude de filtres millimétriques accordables en technologie microfluidique

National audienceCet article présente les travaux initiés au Lab-STICC et au LAAS sur la conception de dispositifs passifs hyperfréquences accordables sur la basse d'une approche microfluidique. L'idée est d'utiliser des micros canaux dans lesquels circulent des fluides. Ces fluides, diélectriques dans un premier temps, sont utilisés pour modifier la permittivité effective d'un substrat sur lequel est réalisée une structure planaire. La perturbation apportée par le fluide diélectrique va ainsi modifier la fréquence de travail du dispositif. En première approche, des stubs quart d'onde et des filtres passe-bande à stubs sont examinés

Design of a Silicon Based Amperometric Microbiosensor Involving NAD-Dependent Dehydrogenase

An electrochemical microbiosensor involving NAD-dependent dehydrogenase has been designed and developed using silicon technology. The sensor is based on a weakly polarized two-gold microelectrode system without any reference electrode. The process allowed mass production of miniaturized devices. An enzymatic solution including diaphorase and NAD-dependent dehydrogenase was confined in the microstructure by means of a semi-permeable membrane. The biocompatibility of the various materials was verified and the gold electrodes were electrochemically characterized. The assay of D-lactic acid was taken as an example using D-lactate dehydrogenase. The sensitivity and detection limit of the microbiosensor were 8 μA mM–1 cm–2 and 0.01 mM respectively. Its lifetime was 3 weeks

Les « systèmes micro-physiologique » : des outils pour modéliser le vivant

National audienceLes "systèmes micro-physiologiques" sont adaptés à l'étude de l'initiation, de la propagation ou du traitement de pathologies telles que le cancer, mais également à des études sur la régénération de tissus, ou à la compréhension d'affections neuronales

A miniaturised silicon based enzymatic biosensor: towards a generic structure and technology for multi-analytes assays

International audienceA miniaturised and generic biosensor has been developed using microsystem technologies for l- and d-lactate, l-malate, l-alanine and ethanol assays. The biosensor is based on the association between an enzymatic solution including diaphorase and dehydrogenases enzymes confined in the microstructure by a membrane and two gold microelectrodes weakly polarised. The pre-treatment of the gold electrode surface is a critical parameter, the sensor sensitivity can be significantly enhanced by processing chemical cleaning steps with sulphochromic solution, H2SO4+H2O2 solution or oxygen plasma. X-ray photoelectron spectroscopy (XPS) analyses put in evidence that the enhanced sensitivity of electrodes can be in part attributed to the removal of an organic contamination. The assays of l-lactate, ethanol and alanine are also presented and compared to d-lactate assay

AN INTEGRATED MAGNETOFLUIDIC DEVICE ENABLING NOVEL ACUTATION FUNCTIONALITIES

International audienceWe report a simple solution for implementing a new set of reconfigurable magnetophoretic functions in a highly integrated hybrid magnetofluidic device. Using a dry film lamination technique, we designed and built a device enabling magnetic actuation of superparamagnetic beads at cell resolution, with attrac-tion and repulsion possibilities, for essential functions such as focusing and trapping

PRODUCTION OF 3-10 µm MICROBUBBLES SUITED FOR ULTRASONIC IMAGING BY 2.5D NANOFLUIDIC DEVICES

International audienceIn this paper, we propose a novel route to generate monodisperse microbubbles (MB) in the range size of 3-10 µm. Using deep reactive ion etching, we designed several "terraces" emulsification devices with depths of 200-1000 nm. We performed characterizations and systematical investigations on critical parameters such as gas pressure, liquid flow rate, and chip geometry. We experimentally show here that MB size is mainly dependent on nanochannel height. The robust monodisperse MB production and the biocompatibility of the materials opens an opportunity to integrate such systems in the future diagnostics routines

An easy surface modification in heterogeneous nano- and micro- fluidic devices

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A new and easy surface functionalization technnology for monitoring wettability in heterogeneous nano- and microfluidic devices

International audienceWe have developed a new and easy surface functionalization technology for monitoring wettability in heterogeneous nano- and microfluidic devices. This technology is based on mussel inspired, dopamine chemistry and it permits to end-graft hydrophilic polymer brushes onto virtually any surface in a low-viscosity regime. We have successfully modified a variety of different solid surfaces, such as Si, SiO2, Ag, Cu, SU8 and PDMS. The modified surfaces were characterized by water contact angle measurements, atomic force microscopy, cyclic voltammetry and by electrokinetic measurements. The adsorption of proteins on the unmodified and modified surfaces was probed with fluorescently labeled albumin. We clearly demonstrated that the studied surfaces became non-fouling when modified with a hydrophilic, polyacrylamide brush, while they remained protein adsorbing when unmodified and/or modified with the dopamine film only. We believe that this universal surface modification approach will be extremely useful in nano- and micro-fluidic devices build from a variety of different materials