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In recent years, innovative cell-based biosensing systems have been developed, showing impact in healthcare and life science research. Now, there is a need to design mass-production processes to enable their commercialization and reach society. However, current protocols for their fabrication employ materials that are not optimal for industrial production, and their preparation requires several chemical coating steps, resulting in cumbersome protocols. We have developed a simplified two-step method for generating controlled cell patterns on PMMA, a durable and transparent material frequently employed in the mass manufacturing of microfluidic devices. It involves air plasma and microcontact printing. This approach allows the formation of well-defined cell arrays on PMMA without the need for blocking agents to define the patterns. Patterns of various adherent cell types in dozens of individual cell cultures, allowing the regulation of cell–material and cell–cell interactions, were developed. These cell patterns were integrated into a microfluidic device, and their viability for more than 20 h under controlled flow conditions was demonstrated. This work demonstrated the potential to adapt polymeric cytophobic materials to simple fabrication protocols of cell-based microsystems, leveraging the possibilities for commercialization.

Cardiovascular disease morbidity has increased worldwide. Organs-on-chips and human pluripotent stem cell (hPSC) technologies aid to overcome some of the limitations in cardiac in vitro models. Here, a bi-compartmental, monolithic heart-on-chip device that facilitates porous membrane integration in a single fabrication step is presented. Moreover, the device includes open-top compartments that allow facile co-culture of hPSC-derived cardiomyocytes and human adult cardiac fibroblast into geometrically defined cardiac microtissues. The device can be reversibly closed with a glass seal or a lid with fully customized 3D-printed pyrolytic carbon electrodes allowing electrical stimulation of cardiac microtissues. A subjacent microfluidic channel allowed localized and dynamic drug administration to the cardiac microtissues, as demonstrated by a chronotropic response to isoprenaline. Moreover, the microfluidic channel can also be populated with human induced pluripotent stem-derived endothelial cells allowing co-culture of heterotypic cardiac cells in one device. Overall, this study demonstrates a novel heart-on-chip model that systematically integrates an open-top device with a 3D printed carbon electrode for electrical pacing and culture of cardiac tissues while enabling active perfusion and dynamic drug dosing. Advances in the engineering of human heart-on-chip models represent an important step towards making organ-on-a-chip technology a routine aspect of preclinical cardiac drug development.

Calcifying algae, like coccolithophores, greatly contribute to the oceanic carbon cycle and are therefore of particular interest for ocean carbon models. They play a key role in two processes that are important for the effective CO2 flux: The organic carbon pump (photosynthesis) and the inorganic carbon pump (calcification). The relative contribution of calcification and photosynthesis can be measured in algae by the amount of particulate inorganic carbon (PIC) and particulate organic carbon (POC). A microfluidic impedance cytometer is presented, enabling non-invasive and high-throughput assessment of the calcification state of single coccolithophore cells. Gradual modification of the exoskeleton by acidification results in a strong linear fit (R2 = 0.98) between the average electrical phase and the PIC:POC ratio of the coccolithophore Emiliania huxleyi 920/9. The effect of different CO2 treatments on the PIC:POC ratio, however, is inconclusive, indicating that there is no strong effect observed for this particular strain. Lower PIC:POC ratios in cultures that grew to higher cell densities are found, which are also recorded with the impedance-based PIC:POC sensor. The development of this new quantification tool for small volumes paves the way for high-throughput analysis while applying multi-variable environmental stressors to support projections of the future marine carbon cycle.

Since the industrial revolution 30% of the anthropogenic CO2 is absorbed by oceans, resulting in ocean acidification, which is a threat to calcifying algae. As a result, there has been profound interest in the study of calcifying algae, because of their important role in the global carbon cycle. The species studied, coccolithophore Emiliania huxleyi, is considered to be globally the single most dominant calcifying algae, which creates a unique exoskeleton from inorganic calcium carbonate platelets. The PIC (particulate inorganic carbon): POC (particulate organic carbon) ratio describes the relative amount of inorganic carbon in the algae and is a critical parameter in the ocean carbon cycle. In this research we explore the use of microfluidic single-cell impedance spectroscopy in the field of calcifying algae. Microfluidic impedance spectroscopy enables us to characterize single-cell electrical properties in a non-invasive and label-free way. We use the ratio of the impedance at high frequency vs. low frequency, known as opacity, to discriminate between calcified coccolithophores and coccolithophores with a calcite exoskeleton dissolved by acidification (decalcified). We have demonstrated that using opacity we can discriminate between calcified and decalcified coccolithophores with an accuracy of 94.1%. We have observed a correlation between the measured opacity and the cell height in the channel, which is supported by FEM simulations. The difference in cell density between calcified and decalcified cells can explain the difference in cell height and therefore the measured opacity.

Organ-on-Chip (OoC) systems culture human tissues in a controllable environment under microfluidic perfusion and enable a precise recapitulation of human physiology. Although recent studies demonstrate the potential of OoCs as alternative to traditional cell assays and animal models in drug development as well as personalized medicine, unmet challenges in device fabrication, parallelization and operation hinder their widespread application. In order to overcome these obstacles, this thesis focuses on the development of the Organ-on-a-Disc technology for the scalable generation and cultivation of microphysiological tissues. Organ-Discs are fabricated using precise, rapid and scalable microfabrication techniques. They enable the pump- and tubing-free perfusion as well as the parallelized generation and culture of tailorable and functional microtissues using rotation-based operations. The Organ-Disc setup is suitable for versatile tissue readouts, treatments and even whole blood perfusion with minimal handling and equipment requirements. Overall, the Organ-Disc creates a scalable and userfriendly platform technology for microphysiological tissue models and paves the way for their transition towards high-throughput systems.:Abbreviations Symbols 1 Introduction 2 Background 2.1 Fluid Dynamics 2.1.1 Flow Equations 2.1.2 Hydraulic Resistance 2.1.3 Wall Shear Stress 2.1.4 Centrifugal Microfluidics 2.2 Microfluidic Chip Fabrication 2.2.1 Chip Materials 2.2.2 Microstructuring 2.2.3 Bonding 3 State of the Art 3.1 Cell Culture Systems 3.2 3D Tissue Generation in Microfluidic Systems 3.3 Organ-on-Chip 3.4 Scale-up of Organ-on-Chip Systems 3.4.1 Scalable Fabrication Technologies 3.4.2 Parallelization Approaches 3.4.3 Integrated Fluid Actuation 3.5 Centrifugal Microfluidics 4 Objectives 5 Materials and Methods 5.1 Organ-Disc Fabrication 5.1.1 Materials 5.1.2 2D Structuring 5.1.3 Hot Embossing Stamp Fabrication TPE Hot Embossing 5.1.4 Bonding Solvent Vapor Bonding Thermal Fusion Bo, In Organ-on-Chip (OoC)-Systemen werden menschliche Gewebe mittels mikrofluidischer Versorgung in einer kontrollierten Umgebung kultiviert und so die Physiologie des Menschen nachgebildet. Obwohl aktuelle Studien zeigen, dass dieser Ansatz Alternativen zu herkömmlichen Zellbasierten Tests und Tiermodellen in der Arzneimittelentwicklung und der personalisierten Medizin bietet, stehen einer breiteren Anwendung Hürden im Bereich der Herstellung, Parallelisierung und Handhabung im Weg. Deshalb ist das Ziel dieser Arbeit die Entwicklung der Organ-on-a-Disc-Technologie, die eine skalierbare Erzeugung und Kultur von mikrophysiologischen Geweben ermöglicht. Für die Herstellung von der Organ-Disc kommen präzise, schnelle und skalierbare Mikrofabrikationsmethoden zum Einsatz. Die Organ-Disc schafft die Basis für die parallelisierte Erzeugung und Kultur von maßgeschneiderten und funktionellen Mikrogeweben, sowie deren Versorgung durch rotationsbasierte Prozesse und ohne zur Hilfenahme von Pumpen oder Schläuchen. Die Organ-Disc eignet sich für unterschiedliche Charakterisierungsmethoden sowie der Gewebestimulation und sogar der Vollblutperfusion mit minimalem Aufwand und Equipment. Insgesamt stellt die Organ-Disc eine skalierbare und benutzerfreundliche Plattformtechnologie für mikrophysiologische Modelle dar und bereitet den Weg für Hochdurchsatzanwendungen.:Abbreviations Symbols 1 Introduction 2 Background 2.1 Fluid Dynamics 2.1.1 Flow Equations 2.1.2 Hydraulic Resistance 2.1.3 Wall Shear Stress 2.1.4 Centrifugal Microfluidics 2.2 Microfluidic Chip Fabrication 2.2.1 Chip Materials 2.2.2 Microstructuring 2.2.3 Bonding 3 State of the Art 3.1 Cell Culture Systems 3.2 3D Tissue Generation in Microfluidic Systems 3.3 Organ-on-Chip 3.4 Scale-up of Organ-on-Chip Systems 3.4.1 Scalable Fabrication Technologies 3.4.2 Parallelization Approaches 3.4.3 Integrated Fluid Actuation 3.5 Centrifugal Microfluidics 4 Objectives 5 Materials and Methods 5.1 Organ-Disc Fabrication 5.1.1 Materials 5