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Les fonctions magnétiques sont aujourd'hui omniprésentes dans les systèmes Lab-on-Chip. Une découverte surprenante est que tandis que la recherche Lab-on-Chip se concentre sur la miniaturisation, les fonctions magnétiques sur puce sont généralement assurées par des aimants centimétriques. Comparés à ces aimants centimétriques, les champs générés par les micro-aimants bénéficient de lois d'échelle conduisant à des gradients de champ considérablement amplifiés et donc à des forces magnétiques proportionnellement accrues. Le but de cette thèse était de démontrer le potentiel des Lab-on-Chips à base de micro-aimants. Les micro-aimants haute performance ont été intégrés avec succès dans les matériaux Lab-on-Chip les plus pertinents, y compris le polymère, le silicium et le papier. Nous avons étudié des fonctions sur puce basées sur l'interaction de structures mécaniques et de micro-aimants actionnés par des gradients magnétiques, des forces et des couples. Enfin, nous avons simulé, fabriqué et testé une variété de nouvelles puces couvrant un large champ d'applications telles que les études cellulaires-mécaniques, la magnétophorèse, la manipulation de fluides sur puce et le diagnostic auprès du patient. Nous concluons que les micro-aimants intégrés présentent un grand potentiel pour les applications de laboratoire sur puce et devraient être plus largement exploités. / Magnetic functions are nowadays ubiquitous in Lab-on-Chip systems. A surprising finding is that while Lab-on-Chip research focalizes on miniaturization, on-chip magnetic functions are usually driven by centimetric magnets. Compared to those centimetric magnets, fields generated by micro-magnets benefit from scaling laws leading to dramatically increased field gradients and thus proportionally improved magnetic forces. The aim of this thesis was to demonstrate the potential of micro-magnet based Lab-on-Chips. High-performance micro-magnets were successfully integrated in the most relevant Lab-on-Chip materials including polymer, silicon and paper. We studied on-chip functions based on the interaction of mechanic structures and micro-magnets actuated by magnetic gradients, forces and torque. Finally, we simulated, fabricated and tested a variety of new chips covering a large field of applications such as cell-mechanics studies, magnetophoresis, on-chip fluid handling and Point-of-Care diagnostics. We conclude that integrated micro-magnets show great potential for lab-on-chip applications and should be more widely exploited.

La détection et quantification d’agent biologique occupe une place prépondérante dans la prévention et la détection des dangers possibles pour la santé publique (épidémie ou pandémie), l’environnement ainsi que d’autres risques contextuelles (bioterrorisme, armes biologique ou chimiques…etc.). Par conséquent, le développement d’un système portable et à moindre coût permettant de détecter ces dangers constitue l’axe de recherche pluridisciplinaire de la collaboration entre différents laboratoires de l’UPMC (Paris 6) et « RWTH university » à Aachen en Allemagne. Dans ce projet, nous avons étudié les aspects pluridisciplinaires d’un microsystème (LoC) électromagnétique de détection immunologique basé sur l’utilisation de nanoparticules magnétiques (MNP). En raison de leur extractabilité et de leur triabilité, les MNP sont adaptées à l'examen d'échantillons biologiques, servant de marqueurs pour des réactions biochimiques. La plupart des techniques classiques de détection existantes sont basées sur des méthodes colorimétrique, fluorescence ou électrochimique qui souffrent en majorité de problème de temps d’analyse et de sensibilité. A cet égard, Les méthodes d’immuno-détection magnétiques constituent une alternative prometteuse. Cette détection est effectuée à l’aide des MNP qui sont spécifiquement bio-fonctionnalisés en surface afin d’être liée à la cible (virus, anticorps…etc). La nouvelle méthode magnétique de mélange de fréquence permet la détection et la quantification de ces MNP avec une grande dynamique. Dans cette thèse, l’effort est dirigé vers la miniaturisation de ce système. Pour ce faire, nous avons développé un ensemble d’outils analytiques et de simulations multiphysiques afin d’optimiser les dimensions des parties électromagnétique (bobines planaires) et microfluidiques. Par la suite, des prototypes de cette structure de détection à partir de bobines en circuits imprimés et de réservoirs microfluidiques en PDMS sont dimensionnés et réalisés. Les performances de ces prototypes ont été évaluées en termes de limite de détection de MNP, linéarité et plage dynamique. En outre, ces prototypes ont permis de valider les outils de dimensionnement réalisés. Une limite de détection de nanoparticules magnétiques de 15ng/mL a été mesurée avec un volume d'échantillon de 14 μL correspondant à une goutte de sang. Finalement, la validation du système quant à l’immuno-détection est abordée avec un état de l’art et le développement d’une procédure de fonctionnalisation biochimique de surface ainsi que des premiers tests pour sa validation. / The detection and quantification of a biological agent or entity has become paramount to anticipate a possible health threat (epidemic or pandemic), environmental threat or to combat other contextual threats (bioterrorism, chemical and biological weapons, drugs). Consequently, developing a portable cost effective device that could detect and quantify such threats is the research focus of the joint multidisciplinary project between UPMC (Paris 6) laboratories and RWTH university in Aachen, Germany. In the framework of this project, we have studied the multidisciplinary aspects of an electromagnetic microsystem for immunologic detection based on magnetic nanoparticles (MNP) in a microfluidic lab-on-chip (LoC). Because of their extractability and sortability, magnetic nanoparticles are adapted for examination of biological samples, serving as markers for biochemical reactions. So far, the final detection step is mostly achieved by well-known immunochemical or fluorescence-based techniques which are time consuming and have limited sensitivity. Therefore, magnetic immunoassays detecting the analyte by means of magnetic markers constitute a promising alternative. MNP covered with biocompatible surface coating can be specifically bound to analytes, cells, viruses or bacteria. They can also be used for separation and concentration enhancement. The novel frequency mixing magnetic detection method allows quantifying magnetic nanoparticles with a very large dynamic measurement range. In this thesis, emphasis is put on the miniaturized implementation of this detection scheme. Following the development of analytical and multiphysics simulations tools for optimization of both excitation frequencies and detection planar coils, first multilayered printed circuit board prototypes integrating all three different coils along with an adapted microfluidic chip has been designed and realized. These prototypes have been tested and characterized with respect to their performance for limit of detection (LOD) of MNP, linear response and validation of theoretical concepts. Using the frequency mixing magnetic detection technique, a LOD of 15ng/mL for 20 nm core sized MNP has been achieved with a sample volume of 14 μL corresponding to a drop of blood. Preliminary works for biosensing have also been achieved with a state of the art of surface functionalization and a developed proposed biochemical immobilization procedure and preliminary tests of its validation.

Die Etablierung der Transkription von kompletten Genen auf planaren Oberflächen soll eine Verbindung zwischen der Mikroarraytechnologie und der Transkriptomforschung herstellen. Darüber hinaus kann mit diesem Verfahren ein Brückenschlag zwischen der Synthese der Gene und ihrer kodierenden Proteine auf einer Oberfläche erfolgen. Alle transkribierten RNAs wurden mittels RT-PCR in cDNA umgeschrieben und in einer genspezifischen PCR amplifiziert. Die PCR-Produkte wurden hierfür entweder per Hand oder maschinell auf die Oberfläche transferiert. Über eine Oberflächen-PCR war es möglich, die Gensequenz des Reportergens EGFP direkt auf der Oberfläche zu synthetisieren und anschließend zu transkribieren. Somit war eine Transkription mit weniger als 1 ng an Matrize möglich. Der Vorteil einer Oberflächen-Transkription gegenüber der in Lösung liegt in der mehrfachen Verwendung der immobilisierten Matrize, wie sie in dieser Arbeit dreimal erfolgreich absolviert wurde. Die Oberflächen-Translation des EGFP-Gens konnte ebenfalls zweimal an einer immobilisierten Matrize gezeigt werden, wobei Zweifel über eine echte Festphasen-Translation nicht ausgeräumt werden konnten. Zusammenfassend kann festgestellt werden, dass die Transkription und Translation von immobilisierten Gensequenzen auf planaren Oberflächen möglich ist, wofür die linearen Matrizen direkt auf der Oberfläche synthetisiert werden können. / In vitro mRNA synthesis and in vitro translation are of great interest for biochemical and molecular biological basic research, and also for biotechnology and other applications. Solid phase coupled synthesis is very useful for the development of high throughput procedures to elucidate and manipulate gene products. An artificial gene was constructed combining the T7 promoter and terminator with the EGFP-gene from the plasmid pEGFP. The functionality of the construct was shown by in vitro translation. The gene-construct was immobilised on a planar glass surface. The transcription was performed on the immobilised gene and mRNA was determined by RT-PCR. These results demonstrate that the complete gene is transcribed from the covalently coupled PCR product. Thus, it is possible to transfer a standard transcription technique onto an On-chip reaction. The direct PCR amplification of transcriptionable sequences of EGFP bound on surfaces was successfully used for solid phase transcription. Successful transcriptions were also performed at least to 1 ng of used template. The RNA synthesis was also successful in the second and third reaction on the same slide as observed by signals after RT-PCR. It seems to be possible to transfer the translation of reportergenes in a solid phase coupled synthesis, too. For further integration of cellular procedures on a chip, the cell-free RNA synthesis on immobilised templates is an crucial technical hurdle to conquer. Major advantages of using immobilised templates for transcription are, low risk of contamination occuring in solution, and no necessity of further purification steps for downstream applications of the RNA product.

La fusion cellulaire est une méthode de génération de cellules hybrides combinant les propriétés spécifiques des cellules mères. Initialement développée pour la production d’anticorps, elle est maintenant aussi investiguée pour l’immunothérapie du cancer. L’électrofusion consiste à produire ces hybrides en utilisant un champ électrique pulsé. Cette technique présente de meilleurs rendements que les fusions chimiques ou virales, sans introduire de contaminant. L’électrofusion est actuellement investiguée en cuve d’électroporation où le champ électrique n’est pas contrôlable avec précision et le placement cellulaire impossible, produisant de faibles rendements binucléaires. Afin d’augmenter le rendement et la qualité de fusion, la capture et l’appariement des cellules s’avèrent alors nécessaires.Notre objectif a été de développer et de réaliser des biopuces intégrant des microélectrodes et des canaux microfluidiques afin de positionner et d’apparier les cellules avant leur électrofusion. Une première structure de piégeage se basant sur des plots isolants et l’utilisation de la diélectrophorèse a été réalisée. Afin d’effectuer des expérimentations sous flux, une méthode de scellement des canaux, biocompatible et étanche a été développée. Puis, le milieu d’expérimentation a été adapté pour l’électrofusion. En confrontant les résultats des expériences biologiques aux simulations numériques, nous avons pu démontrer que l’application d’impulsions électriques induisait la diminution de la conductivité cytoplasmique. Nous avons ensuite validé la structure par l’électrofusion de cellules. Un rendement de 55% avec une durée de fusion membranaire de 6 s a été obtenu. Dans un second temps, nous avons proposé deux microstructures de piégeage pour l’électrofusion haute densité. La première se base sur un piégeage fluidique, alors que la seconde, utilise ladiélectrophorèse sans adressage électrique à l’aide de plots conducteurs. Jusqu’à 75% des cellules fusionnent dans cette dernière structure. Plus de 97% des hybridomes produits sont binucléaires. Le piégeage étant réversible, les hybridomes peuvent ensuite être collectés pour des études ultérieures. / Cell fusion is a method to generate a hybrid cell combing the specific properties of its progenitor cells. Initially developed for antibody production, it is now also investigated for cancer immunotherapy. Electrofusion consists on the production of hybridoma using electric pulses. Compared to viral or chemical methods, electrofusion shows higher yields and this system is contaminant free. Actually, electrofusion is investigated in electroporation cuvettes, where the electric field is not precisely controllable and cell placement impossible, resulting in low binuclear hibridoma yields. To improve the fusion quality and yield, cell capture and pairing are necessary.Our objective was the development and realization of biochips involving microelectrodes and microfluidic channels to place and pair cells prior to electrofusion. A first trapping structure based on insulators and the use of dielectrophoresis has been achieved. In order to perform fluidic experiments, a biocompatible irreversible packaging was developed. Then, the experimental medium was optimized for electrofusion. Confronting the biological experiments and the numerical simulations, we showed that the application of electric pulses leads to a decrease of the cytoplasmic conductivity. The microstructure was validated by cell electrofusion. A yield of 55%, with a membrane fusion duration of 6 s has been achieved. Secondly, we proposed two trapping microstructures for high density electrofusions. The first one is based on a fluidic trapping while the second one uses dielectrophoresis, free of electric wiring, thanks to conductive pads. Up to 75% of paired cells were successfully electrofused with the conductive pads. More than 97% of the hybridoma were binuclear. The trapping being reversible, the hybridoma can be collected for further analysis.

The objective of this work presented here is to extend the capabilities of siloxane waveguide technology in the field of biochemical sensing. Recent advances in the integration of polymeric optical waveguides with electronics onto standard printed circuit boards (PCBs) allow the formation of cost-effective lab-on-achip modules suitable for mass production. This technology has been primarily designed for on-board data communication. The focus of this research is to investigate the possibility of realising a Siloxane polymer based lab-on-chip sensor. Different siloxane-polymer-based optical waveguide sensor structures have been designed and analysed from the aspect of biochemical sensing. An evanescent-wave absorption sensor based on mode-selective asymmetric waveguide junctions is proposed for the first time. The device mitigates the common optical effect of spurious response in absorption sensors due to the analyte transport fluid. Head injury is the leading cause of death in the population of people under 40 years. Currently, 3 out of 5 deaths in emergency rooms are due to severe brain injuries in the developed world. Researchers at the Neurosciences Critical Care Unit (NCCU) at Addenbrooke's Hospital have managed to correlate biochemical changes with the severeness of the injury and the likelihood of patient recovery. Considerable progress has been made to develop a lab-on-chip sensor capable of continuously monitoring glucose, lactate and pyruvate concentrations in the brain fluid, hence the contribution to the current trend in the advancement of portable lab-on-chip technologies for the deployment of point-of-care diagnostic tools. A novel recognition layer has been developed based on porphyrin in combination with glucose, lactate and pyruvate oxidase for measuring all the analytes, enabling fast and reversible chemical reactions to be monitored by optical interrogation. The operational wavelength of the developed recognition layer is 425 nm, which required the formation of polymer features that were beyond the fabrication capabilities at the time. Through considerable process development and the adoption of nanoimprinting lithography, siloxane polymer based optical waveguides were fabricated allowing the realisation of highly sensitive optical sensors. Based on the results that are presented here, it can be concluded the functionalization of siloxane polymer waveguide have a potential for realising biochemical sensors in the future. The new fabrication technique will allow the formation of more robust and complex lab-on-chip sensors based on this material.

L’intérêt des ultrasons pour la caractérisation de milieux ou pour l’actionnement à plus forte puissance n’est plus à démontrer. L’intégration de fonctions acoustiques substrats de silicium soulève en revanche de nombreux problèmes technologiques. Le travail de thèse présenté fait suite aux premiers développements technologiques qui ont permis la validation du concept de caractérisation acoustique haute fréquence en canal microfluidique. Les principales avancées de ce travail concernent l’optimisation du transfert de l’énergie acoustique dans le canal microfluidique dans une bande de fréquence allant de 500 à 1000 MHz. Des dépôts de couches minces sur les miroirs et le développement de transducteurs en couches épaisses constituent les principales avancées. Une première évaluation de l’actionnement de fluides ou de particules en canal microfluidique est également présentée ainsi qu’une application du système à la mesure de température en canal microfluidique par ultrasons. / The interest of ultrasounds for media characterization or for actuation when using more power is well known. Nevertheless, the integration of these acoustic functions in silicon based Lab-on-chips requires specific technological developments. The possibility to use high frequency bulk acoustic waves in this kind of systems for characterization or detection has been presented previously in another PhD work. The main objective of this work was to optimize acoustic energy transfer to a microfluidic channel in a frequency range between 500 MHz and 1000 MHz. To do that, the main technological developments achieved among others concern the coating of the guiding mirrors to avoid acoustic mode conversion and ZnO thick films sputtering for the fabrication of piezoelectric transducers. The developed system has been used for particles detection or concentration evaluation. Moreover, a first evaluation of fluids/particles actuation was demonstrated, along with temperature evaluation using ultrasound were achieved in microfluidic channels.

Photonic crystals serve as powerful building blocks for the development of lab-on-chip devices. Currently they are used for a wide range of miniaturized optical components such as extremely compact waveguides to refractive-index based optical sensors. Here we propose a new technique for analyzing and characterizing cells through the design of a micro-flow cytometer using photonic crystals. While lab scale flow cytometers have been critical to many developments in cellular biology they are not portable, difficult to use and relatively expensive. By making a miniature sensor capable of replicating the same functionality as the large scale units with photonic crystals, we hope to produce a device that can be easily integrated into a lab-on-chip and inexpensively mass produced for use outside of the lab. Using specialized FDTD software, the proposed technique has been studied, and multiple important flow cytometry functions have been established. As individual cells flow near the crystal surface, transmission of light through the photonic crystal is influenced accordingly. By analyzing the resulting changes in transmission, information such as cell counting and shape characterization have been demonstrated. Furthermore, correlations for simultaneously determining the size and refractive indices of cells has been shown by applying the statistical concepts of central moments.

A microfluidic lab-on-a-chip (LOC) device for in-situ synthesis of gold nano-particles was developed. The long term goal is to develop a portable hand-held diagnostic platform for monitoring water quality (e.g., detecting metal ion pollutants). The LOC consists of micro-chambers housing different reagents and samples that feed to a common reaction chamber. The reaction products are delivered to several waste chambers in a pre-defined sequence to enable reagents/ samples to flow into and out of the reaction chamber. Passive flow actuation is obtained by capillary driven flow (wicking) and dissolvable microstructures called ‘salt pillars’. The LOC does not require any external power source for actuation and the passive microvalves enable flow actuation at predefined intervals. The LOC and the dissolvable microstructures are fabricated using a combination of photolithography and soft lithography techniques. Experiments were conducted to demonstrate the variation in the valve actuation time with respect to valve position and geometric parameters. Subsequently, analytical models were developed using one dimensional linear diffusion theory. The analytical models were in good agreement with the experimental data. The microvalves were developed using various salts: polyethylene glycol, sodium chloride and sodium acetate. Synthesized in-situ in our experiments, gold nano-particles exhibit specific colorimetric and optical properties due to the surface plasmon resonance effect. These stabilized mono-disperse gold nano-particles can be coated with bio-molecular recognition motifs on their surfaces. A colorimetric peptide assay was thus developed using the intrinsic property of noble metal nano-particles. The LOC device was further developed on a paper microfluidics platform. This platform was tested successfully for synthesis of gold nano-particles using a peptide assay and using passive salt-bridge microvalves. This study proves the feasibility of a LOC device that utilizes peptide assay for synthesis of gold nano-particles in-situ. It could be highly significant in a simple portable water quality monitoring platform.

Cellulose is a biodegradable, renewable, flexible, inexpensive, biopolymer which is abundantly present in nature. In spite of these inherent advantages, cellulose fibers cannot be used directly in a number of potential industrial applications because of their hydrophilic nature; a surface modification is often required to alter the surface properties of cellulose. This thesis work reports a fabrication method that results in superhydrophobic properties (contact angle (CA) > 150°) on cellulose (paper) surfaces. Superhydrophobicity was obtained by domain-selective etching of amorphous portions of the cellulose fiber in an oxygen plasma, and by subsequently coating the etched surface with a thin fluorocarbon film deposited via plasma enhanced chemical vapor deposition from a pentafluoroethane precursor. Two forms of superhydrophobicity with vastly different degrees of adhesion were obtained by varying the plasma treatment conditions, in particular the duration of oxygen etching: "roll-off" (contact angle (CA): 166.7° ± 0.9° and CA hysteresis: 3.4° ± 0.1°) and "sticky" (CA: 153.4° ± 4.7° and CA hysteresis: 149.8±5.8°) superhydrophobicity. The CA hysteresis could be tuned between the two extremes by adjusting the oxygen etching time to control the formation of nano-scale features on the cellulose fibers. The effects of fiber types (soft vs. hard wood) and paper making parameters on fabricating superhydrophobic paper were also investigated. There were no significant differences in the formation of the nano-scale features created via oxygen etching on paper substrates obtained from different fiber types and paper making parameters. Because "roll-off" superhydrophobicity is primarily determined by the nano-scale roughness, this property is therefore not significantly affected by the fiber types or paper making parameters. While the fiber type does not affect "roll-off" or "sticky" superhydrophobicity, paper making process parameters affect the structure of the paper web on the micro-scale and thus lead to variations in "sticky" superhydrophobicity. Superhydrophobic paper substrates were patterned with high surface energy ink deposited using a commercial desktop printer. The patterns could be used to manipulate the drag and extensional adhesion of water drops on the substrates. Classic 'drag' and 'extensional' adhesion expressions were used to model the behavior of water drops on basic dot and line patterns of variable dimensions. A fundamental understanding of the adhesive forces of water drops as a function of pattern shape and size was thus obtained. Based on this knowledge, patterned paper substrates were then designed and fabricated to perform simple unit operations, such as storage, transfer, mixing and merging of water drops. These basic functionalities were combined in the design of a simple two-dimensional lab-on-paper (LOP) device. Further studies of more complicated pattern shapes led to the generation of patterns that allowed directional mobility and tunable adhesion of water drops. These developments are critical for designing novel components for two-dimensional LOP devices such as flow paths, gates/diodes, junctions and drop size filters.