Overview of Materials for Microfluidic Applications

For each material dedicated to microfluidic applications, inherent microfabrication and specific physico‐chemical properties are key concerns and play a dominating role in further microfluidic operability. From the first generation of inorganic glass, silicon and ceramics microfluidic devices materials, to diversely competitive polymers alternatives such as soft and rigid thermoset and thermoplastics materials, to finally various paper, biodegradable and hydrogel materials; this chapter will review their advantages and drawbacks regarding their microfabrication perspectives at both research and industrial scale. The chapter will also address, the evolution of the materials used for fabricating microfluidic chips, and will discuss the application‐oriented pros and cons regarding especially their critical strategies and properties for devices assembly and biocompatibility, as well their potential for downstream biochemical surface modification are presented

Molecular Microfluidic Bioanalysis: Recent Progress in Preconcentration, Separation, and Detection

This chapter reviews the state-of-art of microfluidic devices for molecular bioanalysis with a focus on the key functionalities that have to be successfully integrated, such as preconcentration, separation, signal amplification, and detection. The first part focuses on both passive and electrophoretic separation/sorting methods, whereas the second part is devoted to miniaturized biosensors that are integrated in the last stage of the fluidic device

Fonctionnalisation de surface et intégration de colloïdes par assemblage dirigé

We present here a surface patterning process based on the directed assembly of colloids in a suspension. The technique uses a suspension drop which is dragged along a surface with or without structures. Due to capillary or hydrodynamic forces, colloids self-organize on the surfaces. This directed assembly process has been successfully used for the organization of particles at high speed. We focused our interest on the capture of magnetic particles that can be used as anchor points for the formation of magnetic columns. We developed several applications dedicated to the capture of cells in biological fluids, the fabrication of artificial microcilia and the development of force sensors. In the latter case, the stiffness of magnetic columns has been measured depending on several parameters, allowing us to estimate the forces acting on them by monitoring their deflection. These assembly techniques have been extended to the capture and deposition of yeasts or bacteria cells on surfaces. In the case of mammalian cells, specific patterns were designed for the selective trapping of colloids, thus allowing the creation of imbricated networks of different populations of particles. When functionalized with antibodies, these particles can induce the capture of a specific cell type. Such networks of particles can be used to create complex cells assemblies with precise localization.Nous présentons des procédés de fonctionnalisation de surface par assemblage dirigé de colloïdes en suspension. La motivation de ce projet est de montrer que des techniques simples fondées sur des phénomènes de démouillage de suspensions colloïdales permettent de diriger le dépôt de particules sur des surfaces structurées, de façon déterministe avec une résolution micrométrique. L'objectif de ces travaux est de développer une technique de structuration simple, polyvalente et utilisable en routine. Deux verrous technologiques majeurs ont été levés : d'une part l'optimisation des paramètres d'assemblage a permis d'étendre considérablement les vitesses d'assemblage et d'autre part, l'optimisation des structures de capture à rendu possible le multiplexage des dépôts et la création de réseaux imbriqués de particules de types différents. Ce processus a été appliqué avec succès à des particules magnétiques. Ces particules fixées à la surface peuvent servir de points d'ancrage pour des colonnes magnétiques. Plusieurs exemples d'applications telles que la capture de cellules au sein de liquides biologiques, la fabrication de micro-flagelles artificielles, ou de micro-capteurs de force ont été développées. Ces techniques ont également été adaptées pour l'assemblage de cellules, de levures et de bactéries sur des surfaces. Cela a conduit au développement de substrats de capture et de mise en culture permettant la création de réseaux constitués de plusieurs types de cellules précisément localisées

Dielectric properties of a single nanochannel investigated by high-frequency impedance spectroscopy

International audienceHigh-frequency electric impedance spectroscopy is used to characterize the dielectric properties of a singlenanochannel in a micro/nanofluidic device. The simulated electric impedance results lead to the determinationof two conductance regimes, a non-ideal capacitance and its surface charge

High throughput micropatterning of interspersed cell arrays using capillary assembly This content has been downloaded from IOPscience. Please scroll down to see the full text. High throughput micropatterning of interspersed cell arrays using capillary assembly

International audienceA novel technology is reported to immobilize different types of particles or cells on a surface at predefined positions with a micrometric precision. The process uses capillary assembly on arrays of crescent-shaped structures with different orientations. Sequential assemblies in different substrate orientations with different types of particles allow for the creation of imbricated and multiplexed arrays. In this work up to four different types of particles were deterministically localized on a surface. Using this process, antibody coated microparticles were assembled on substrates and used as capture patterns for the creation of complex cell networks. This new technology may have numerous applications in biology, e.g. for fast cell imaging, cell-cell interactions studies, or construction of cell arrays

Electropreconcentration diagrams to optimize molecular enrichment with low counter pressure in a nanofluidic device

International audienceIon-concentration-polarization (ICP) - based focusing electrokinetics nanofluidic devices have been developed in order to simultaneously detect and enrich very diluted analytes on chip. However, stabilization of focal points over long time under the application of the electric field remains as a technical bottleneck. If pressure-assisted preconcentration methods have been proposed to stabilize propagating modes at 1⁄Du ≪1, these recent protocols remain laborious for optimizing experimental parameters. We report “field/pressure” E/P diagrams for fluorescein where the typical regimes, i.e. propagating focusing, stable focusing and stacking can be observed. The region of stable focusing is shown to vary depending of the nanoslit length (100µm < Lnanoslit < 500µm) and the nature of the background electrolyte (BGE) (KCl and NaCl). Longer nanoslits (500µm) produce stabilization at low pressure, whereas NaCl BGE offers a narrower and more fluorescent stable window in the E/P diagram compared to KCl. Finally, the ability of such pressure-assisted protocol to concentrate negatively charged proteins has been tested with 10µM ovalbumin in HEPES and the corresponding E/P diagram for ovalbumin confirms the existence of a stable focusing regime at low electric field

Evaluation of In-Flow Magnetoresistive Chip Cell—Counter as a Diagnostic Tool

International audienceInexpensive simple medical devices allowing fast and reliable counting of whole cells are of interest for diagnosis and treatment monitoring. Magnetic-based labs on a chip are one of the possibilities currently studied to address this issue. Giant magnetoresistance (GMR) sensors offer both great sensitivity and device integrability with microfluidics and electronics. When used on a dynamic system, GMR-based biochips are able to detect magnetically labeled individual cells. In this article, a rigorous evaluation of the main characteristics of this magnetic medical device (specificity, sensitivity, time of use and variability) are presented and compared to those of both an ELISA test and a conventional flow cytometer, using an eukaryotic malignant cell line model in physiological conditions (NS1 murine cells in phosphate buffer saline). We describe a proof of specificity of a GMR sensor detection of magnetically labeled cells. The limit of detection of the actual system was shown to be similar to the ELISA one and 10 times higher than the cytometer one