One-step fabrication of microchannels with integrated three dimensional features by hot intrusion embossing

We build on the concept of hot intrusion embossing to develop a one-step fabrication method for thermoplastic microfluidic channels containing integrated three-dimensional features. This was accomplished with simple, rapid-to-fabricate imprint templates containing microcavities that locally control the intrusion of heated thermoplastic based on their cross-sectional geometries. The use of circular, rectangular and triangular cavity geometries was demonstrated for the purposes of forming posts, multi-focal length microlense arrays, walls, steps, tapered features and three-dimensional serpentine microchannels. Process variables, such as temperature and pressure, controlled feature dimensions without affecting the overall microchannel geometry. The approach was demonstrated for polycarbonate, cycloolefin copolymer and polystyrene, but in principle is applicable to any thermoplastic. The approach is a step forward towards rapid fabrication of complex, robust, microfluidic platforms with integrated multi-functional elements

One-Step Fabrication of Microchannels with Integrated Three Dimensional Features by Hot Intrusion Embossing

We build on the concept of hot intrusion embossing to develop a one-step fabrication method for thermoplastic microfluidic channels containing integrated three-dimensional features. This was accomplished with simple, rapid-to-fabricate imprint templates containing microcavities that locally control the intrusion of heated thermoplastic based on their cross-sectional geometries. The use of circular, rectangular and triangular cavity geometries was demonstrated for the purposes of forming posts, multi-focal length microlense arrays, walls, steps, tapered features and three-dimensional serpentine microchannels. Process variables, such as temperature and pressure, controlled feature dimensions without affecting the overall microchannel geometry. The approach was demonstrated for polycarbonate, cycloolefin copolymer and polystyrene, but in principle is applicable to any thermoplastic. The approach is a step forward towards rapid fabrication of complex, robust, microfluidic platforms with integrated multi-functional elements

Development of a robust microfluidic electrochimical cell for biofilm study in controlled hydrodynamic conditions

Le domaine de la bioélectrochimie a actuellement un grand impact sur les nouvelles biotechnologies, notamment les dispositifs médicaux aux points de service et la détection bioélectrochimique. D'autre part, les systèmes émergents de bioénergie offrent de nouvelles opportunités pour se passer des produits pétroliers classiques grâce à des approches alternatives plus durables sur le plan environnemental. En tant que telle, la branche de la bioélectrochimie traitant des systèmes énergétiques est sur le point d’avoir un impact incontestable sur les concepts d’énergie verte et de bioénergie. Pour faciliter ces études et d'autres, les systèmes bioélectrochimiques (BES), qui utilisent des composants biologiques tels que des bactéries (souvent appelées biocatalyseurs), sont de plus en plus développés et miniaturisés pour une nouvelle série de biotechnologies. Cette thèse porte sur la fabrication et la fonctionnalité d’un « système microfluidique électrochimique à trois électrodes » pour l’étude de biofilms de différentes bactéries (électroactives et non-électroactives) à l’aide de différentes techniques électrochimiques. Ces biofilms ont été largement étudiés par des techniques électrochimiques et d’imagerie microscopique (microscopie optique et électronique). Cette thèse pourra potentiellement ouvrir la voie à une nouvelle vague de développements de biocapteurs électrochimiques, tout en offrant des avancées scientifiques spécifiques dans les études de biocapacité de biofilm, de biorésistance, de pH du biofilm, de dépendance nutritionnelle de l'activité du biofilm et de la cinétique de respiration bactérienne.The area of bioelectrochemistry is currently making the greatest impact in new biotechnology, including point of care medical devices and bioelectrochemical sensing. On the other hand, emerging bioenergy systems offer new opportunities to move away from conventional petroleum products toward more environmentally sustainable alternative approaches. As such, the branch of bioelectrochemistry dealing with energy systems is poised to have an undoubtable impact on greenenergy and bioenergy concepts. To facilitate these and other areas of study, bioelectrochemical systems (BESs), which use biological components such as bacteria (often referred to as biocatalysts) are increasingly being developed and miniaturized for a new round of biotechnology. This PhD thesis focuses on fabrication and functionality of a “three-electrode electrochemical microfluidic system” for biofilm studies of different bacteria (electroactive and non-electroactive) using different electrochemical techniques. They were broadly studied by electrochemical and microscopic imaging (optical and electron microscopy) techniques. This thesis can potentially open the way for a new wave of electrochemical biosensor development, while offering specific scientific advances in studies of biofilm biocapacitance, bioresistance, biofilm pH, nutrient dependency of biofilm activity and bacterial respiration kinetics

High-precision micro-machining of glass for mass-personalization

With the fourth industrial revolution manufacturing industry faces new challenges. Small batches of personalized parts, where the geometry changes per part, must be produced in an economically viable manner. In such cases of mass personalization new manufacturing technologies are required which can keep manufacturing overhead related to change of part geometries low. These processes need to address the issues of extensive calibration and tooling costs, must be able to handle complex parts and reduce production steps. According to recent studies hybrid technologies, including electrochemical technologies, are promising to address these manufacturing challenges. At the same time, glass has fascinated and attracted much interest from both the academic and industrial world, mainly because it is optically and radio frequency transparent, chemically inert, environmentally friendly and it has excellent mechanical and thermal properties, allowing tailoring of new and dedicated applications. However, glass is a hard to machine material, due to its hardness and brittleness. Machining smooth, high-aspect ratio structures is still challenging due to long machining times, high machining costs and poor surface quality. Hybrid methods like Spark Assisted Chemical Engraving (SACE) perform well to address these issues. Nevertheless, SACE cannot be deployed for high-precision glass mass-personalization by industry and academia, due to 1) lack of process models for glass cutting and milling, relating SACE input parameters to a desired output, 2) extensive calibration needed for tool-workpiece alignment and tool run-out elimination, 3) part specific tooling required for proper clamping of the glass workpiece to attain high precision. In this study, SACE technology was progressively developed from a mass-fabrication technology towards a process for mass-personalization of high-precision glass parts by addressing these issues. Key was the development of 1) an (empirically validated) model for SACE cutting and milling process operations allowing direct relation of the machining input to the desired machining outcome, enabling a dramatical increase of automation across the manufacturing process workflow from desired design to establishing of machinable code containing all necessary manufacturing execution information, 2) in-situ fabrication of the needed tooling and 3) the use of low-cost rapid prototyping, eliminating high indirect machining costs and long lead times. To show the viability of this approach two novel applications in the microtechnology field were proposed and developed using glass as substrate material and SACE technology for rapid prototyping: a) fabrication of glass imprint templates for microfabricating devices by hot embossing and b) manufacturing of glass dies for micro-forming of metal micro parts