This report presents a route map and the first steps to the development of a vascularised alveolarcapillary barrier to study the effects of air pollution on lung-health and chronic respiratory diseases. The ultimate goal is to fabricate a vascularised model of an alveolar-capillary barrier, that mimics the physiology of the human lung more closely than currently used models. Current vascularised alveolar-capillary barrier models are limited by the absence of membrane-free designs and the lack of integration of both fluid flow and membrane stretching. The development of a membrane-free, vascularised model that integrates fluid flow and membrane stretching, requires a reproducible vascularisation method with a lifespan sufficient for epithelial cell differentiation and follow-up experiments. Pre-structured vessels provide more control of the structure of the vessel network and improve the reproducibility of a model compared to a model with a self-assembled vascular network. Therefore, the first step in this study is to establish a method for culturing a lung-derived endothelial vessel in a pre-formed channel within hydrogel as extracellular matrix that can last several weeks. Wire moulding is used to create a hollow channel inside a fibrinogenbased hydrogel between two injection needles. Two diameters of wires, 50 μm and 125 μm, and two concentrations, 1% and 2%, of fibrinogen were used for a total of 10 tests. The endothelial cells were seeded using the capillary effect and after four hours, the perfusion of medium through the channels started. A pre-formed channel in the hydrogel containing 2% hydrogel and seeded with lung-derived endothelial cells remained perfusable for 32 days while withstanding flow leading to a significant amount of shear stress on the endothelial cells. To study the phenomena of gas exchange that accur across larger tissue constructs, the hierarchical dimensions and topological complexity of native vascular beds should be better replicated. Another moulding method is needed to create a structure of hollow channels inside a hydrogel to culture a vascular network rather than one vessel. It was found that with carbohydrate glass, varying structures can be printed and it can be embedded within hydrogel prior to cross-linking without blending into one another. This indicates that sacrificial moulding using carbohydrate glass is a promising technique for creating pre-structured vascularised networks. This potential method to create a pre-structured network combined with our cell seeding method and the 2% fibrinogen hydrogel, is the basis for the development of a reproducible, membrane-free vascularised alveolar-capillary barrier model that incorporates flow and stretching of the barrier.

Current stroke treatments are limited to acute phase management, and there are few clinically available drugs for neuron protection or damage repair due to restrictions imposed by the blood-brain barrier. This project envisions an implantable DDS for precise drug dispensing to areas of the brain affected by stroke, using light-activated liposomes and microfluidic control to improve therapeutic effectiveness and minimize off-target side effects.

Reviewing literature on microfluidic trap-and-release mechanisms, it became evident that deformable particles often tend to slip out of traps. To accurately predict this behavior, the Young's-Laplace equation and energy stored in the liposome membrane have been assessed. Next, microfluidic devices that were able to manipulate the liposomes to the desired trapping locations were designed and produced. The trapping behavior of liposomes has been assessed by increasing the hydrostatic pressure under a fluorescent microscope. The results show that the experimental pressure of 50-250 Pa is lower than the expected theoretical predictions and that there exists a diameter threshold of 17-18 μm for which the liposomes show lysis behavior. Finally, the entire DDS concept has been demonstrated using a network of traps using the path-of-least-resistance approach.

In Additive Manufacturing (AM), typically a trade-off exists between part quality and build time. Part orientation with respect to the print direction may significantly influence both. In this thesis, the consequences of part orientation on support volume requirements are studied. Build time, material consumption, and post-processing efforts are influenced by the amount and configuration of required supports. Using triangular surface meshes, the support requirement for a given part orientation is calculated for each triangle facet individually and summed. Gradient descent methods are used to optimize part orientation for minimum support volume. To enable implementation of gradient descent optimization, focus is placed on obtaining derivative information of the support volume on a per-facet basis. The resulting support volume function contains discontinuities, for which smooth
approximation strategies are implemented. This approach is first applied to convex shapes, with promising results. For non-convex shapes however, non-local information is required. A novel method for indicating the presence of on-part supports is presented. All possible candidates for support on part are computed for each facet before the start of the optimization process. The resulting connectivity set is an inherent property of the shape and only requires calculation once. The new method is tested using numerical experiments, which indicate that gradient-based optimization of the smooth volume
function outperforms the population-based approaches commonly used in the literature. Moreover, the presented work provides a framework for optimizing total part cost in which other metrics are easily appended.

Mechanical forces are integral to the functionality and behavior of biological systems, from the cellular to the molecular level. Acoustic force spectroscopy (AFS), an emerging field, seeks to explore these intricate dynamics. Traditional methods in AFS, particularly those using bulk acoustic wave (BAW) devices, still lack sample visibility and have a low throughput. These limitations hinder the amount and type of data that can be gathered in the study of cellular and molecular mechanics. This research project addresses the challenge of enhancing visibility and throughput in AFS by developing a novel BAW device. Here we show the fabrication and implementation of a glass transversal resonator by femtosecond laser ablation and a simple glass-glass bonding technique using polyethylene film and cyanoacrylate glue, which enables two-dimensional particle trapping. Compared to existing BAW setups in AFS, our approach offers improved sample visibility and is capable of positioning particles at arbitrary locations between half- and full-wave mode equilibria by rapid mode-switching. It shows that the position can be predicted using a straightforward method to determine the stiffness of each mode. This advancement of acoustic force spectroscopy could pave the way for new approaches in biomedical research. For example, the ability to alter the force field in a predictable manner allows to form both force- and distance-clamps. More functional BAW devices could thereby not only enhance our understanding of cellular processes but also find broader application in fields like tissue engineering and medical diagnostics.