We present a low-cost, camera-based tactile sensor that leverages the photoelastic effect—interference fringes that appear under stress—to estimate contact force, position, and shape. Each fringe image is recorded at 50 Hz and processed by a multi-task neural network that predicts (i) the normal force (Fz ), (ii) the 2D contact location (x, y), and (iii) the shape class of the object. Two sensor variants were developed: Sensor 1, a layered design with fewer visible fringes, and Sensor 2, an integrated structure with improved fringe clarity. Both were evaluated using a ResNet-18 and a lightweight custom CNN, under three augmentation pipelines: grayscale images with 10 noisy augmented samples each, RGB images with 3 noisy augmentations, and RGB images with 3 clean (noise-free) augmentations. The base dataset includes nearly 15,000 synchronised samples of high-frequency fringe images and force signals. With augmentation, this was expanded to around 45,000 or 150,000 samples depending on the pipeline. The best results were achieved using Sensor 1 and ResNet-18 trained on grayscale images with 10 augmentations per input image. This configuration yielded a force MSE of 0.0213 N2, a contactpoint RMSE of 0.4462 mm, and 96.24% shape classification accuracy. Notably, even RGB images with only three augmentations per sample reached similar performance levels. These findings highlight that full-colour input and lightweight augmentation remain effective for accurate, scalable tactile sensing. Our modular learning pipeline generalises across sensor variants and data regimes, enabling robust, highfrequency tactile inference suitable for real-world deployment.

Thermoplastic matrices reinforced with natural fibres offer a promising solution toward the
development of sustainable composite materials, which provide the potential for recyclability
while lowering environmental impact. This research is particularly relevant to the growing
sustainability concerns about WTBs (Wind Turbine Blades), predominantly manufactured from
thermoset composites that are very difficult to recycle. These present huge EoL challenges due
to the inability to efficiently process decommissioned WTBs, often leading to landfilling or
energy-intensive recycling methods. In such a context, this work addresses the development of
f
lax fibre-reinforced thermoplastic composite tapes via a lab-scale vertical pultrusion process.
The focus will be to optimize melt pool temperature, pulling speed, and die geometry for high
quality, recyclable composites that are suitable for wind energy applications.
A custom machine was designed and produced to allow the combination of flax fibre twisted
yarns and melted thermoplastic to make composite tapes by pultrusion. The influences of some
key variables, for instance, consolidating die length, pulling speed, and processing temperature,
on surface texture, void content, and fibre impregnation were studied. The results indicated that
using a shorter consolidating die along with higher pulling speeds and high pultrusion
temperatures, caused increased surface roughness. However, with an increase in the yarn count
to reduce the gap between the fibres, the surface texture for the samples treated at 190°C
(highest temperature tested) was significantly reduced.
Ultrasonic welding was also done, followed by lap shear tests to evaluate the weldability and
mechanical strength of the tapes produced with the vertical pultrusion setup compared to
benchmark samples. It was noted that the tapes processed at 190°C showed better mechanical
properties compared to tapes processed at 170°C, which could be related to better fibre
impregnation and higher crystallinity of tapes. Overall, the testing of welded samples showed that
the mechanical properties of pultruded tapes were significantly superior compared to
benchmark samples, as a result of stronger fibre-matrix bonding and considerably higher surface
quality.
Future work should focus on refining die designs to further explore the effect of long tapered die
sections, performing detailed crystallinity analyses, and employing advanced void measurement
techniques.

Injection molding is a widely used process for manufacturing a large range of polymer parts, including fiber-reinforced polymer composites. The complex nature of this process, combined with the non-Newtonian behavior of molten polymers, implies significant challenges in terms of control, prediction, and optimization of the processing parameters that influence manufacturing quality. While various computational and numerical models have been proposed to simulate the injection molding process and ensure the desired part quality (see, for instance, industrial software such as Moldex3D or Moldflow, they bring their own challenges, including high computational costs, the need for solver tuning, frequent parametric studies, and the economic burden associated with licensing.

In this study, machine learning surrogates are explored as an alternative to conventional modeling software. They are based on Graph Neural Networks (GNNs) that have recently demonstrated remarkable potential for simulating physical systems. In a graph, physical systems are encoded as nodes end edges, capturing their organization. Then, state-of-the-art techniques such as the message passing framework are tested for their potential to learn physics. In the long term, this project aims to establish a novel graph-based framework capable of efficiently simulating complex physics across various material models and processing conditions.

A numerical model is developed for 2D mold filling and quantitively validated against a benchmark. The prediction results demonstrate that the learned simulator is able to capture the physics of melt front behavior. Further, the prediction runtime is significantly faster than the ground truth, completing in under 1 second compared to \textasciitilde hours, representing a substantial improvement in efficiency. However, the accuracy of the predictions can vary, with errors accumulating especially during testing. While the scalar loss metric provides an estimate of the model's performance, it lacks expressiveness and can be unreliable on its own.

The growing amount of plastic waste generated by the consumer goods industry has led to excessive landfilling and increased greenhouse gas emissions, contributing significantly to the greenhouse effect. Government initiatives have identified the potential for a more sustainable approach to managing this homogeneous plastic waste stream. The Netherlands Circular Economy Program 2023-2030 (NCEP) envisions the MEGA project as a solution to repurpose plastic waste by replacing aging pedestrian infrastructure. Polypropylene (PP), known for its chemical stability and weather resistance, can be reinforced with glass fibers (rPP-G) to meet the requirements of such applications. Additionally, 3D printing is recognized as a promising method to reduce plastic waste during production, making it a valuable component of this initiative.

Nevertheless, outdoor infrastructural applications are subjected to load and temperature cycling due to their exposure to varying weather conditions, static loads, and pedestrians walking at different frequencies. This study aimed to assess and evaluate the effects of hygrothermal aging on the mechanical behavior of rPP-G. Three conditions were studied: a control condition not subjected to the aging environment, an extreme condition subjected to 95 % relative humidity (R.H.) and 80 ◦C, and a condition that approximated real application humidity levels of 77 % R.H. at the same temperature.

The tensile properties were evaluated by applying the load at a speed of 1 mm/min. The dynamic mechanical response was investigated at frequencies of 1 Hz and 2 Hz to simulate a crowd walking and a crowd brisk-walking on the material. The creep response was examined through short-term creep tests at elevated temperatures, and a methodology was derived based on the Time-Temperature Superposition (TTS) principle to extrapolate the behavior at ambient temperatures for stress levels of 8 and 10 MPa. For further analysis of the results, Scanning electron microscopy (SEM) captures were acquired, and the IR spectrum and diffraction pattern of rPP-G under different aging conditions was measured. The tensile properties suggested increasing degradation with hygrothermal effects, leading to a 14.3 % reduction in ultimate tensile strength (UTS), a 16 % reduction in Young’s modulus, and a 93.3 % increase in strain at break. This indicated weakening of the fiber/matrix interface, verified by increased fiber pull-out. However, no hydrolytic degradation was observed, as no differences in chemical compounds and crystallinity were detected. The dynamic mechanical response suggested the existence of two mechanisms: water acting as a stiffener at cryogenic temperatures, and induced plasticization and fiber/matrix weakening from the hygrothermal effects. However, fiber/matrix weakening dominated under extreme aging conditions, hindering the stiffening effects of water on the molecular structure of rPP-G. This effect was more pronounced under median aging conditions for the 1 Hz loading, as more time allowed for molecular relaxation. Increasing frequencies appeared to shift the glass transition temperature (Tg) to higher temperatures, highlighting the material’s elastic character. The creep response of rPP-G revealed an exponential relationship between temperature and time to fracture, allowing the use of Time-Temperature Superposition (TTS) with the Arrhenius equation to predict its behavior at ambient temperatures. The derived methodology suggested that hygrothermal effects leading to the degradation of tensile properties are significantly more apparent under long-term load applications, revealing a 282.6% reduction of time to fracture at 8 MPa under extreme conditions.

This thesis demonstrated the significance of dynamic mechanical analysis in understanding the effects of degradation on reinforced thermoplastic polymers. Additionally, it highlighted the importance of creep testing for such applications, revealing crucial insights into the long-term load application effects on the service life of thermoplastic polymers.

Organ-on-a-chip (OoC) technology has revolutionized the biomedical research field by offering dynamic platforms which accurately mimic physiological environments of human tissue. This technology has become a promising option to study human biology in vitro, including disease modeling, drug screening and personalized medicine. Organoids, 3D cell cultures derived from human stem cells, represent a promising tool to investigate 3D tissue growth in vitro. However, integration of vasculature in these organoids remains a significant challenge. Establishment of vasculature is essential to enable significant organoid growth, allowing nutrient and oxygen supply and waste removal.

This report aims to develop a Pluronic F127 based hydrogel as a transient barrier in an OoC-platform that combines cell cultures of Vasculature-on-a-Chip and cortical brain organoids. This transient barrier separates the two cell cultures until sufficient maturation of the cortical organoid. Due to thermoreversible gelation, the Pluronic F127 hydrogel barrier can be removed from the barrier channel by a decrease in temperature. Pluronic F127 and di-acrylated Pluronic F127 hydrogels were synthesizes and characterized using rheometry, differential scanning calorimetry and degradation testing to determine the optimal Pluronic F127 hydrogel. Simultaneously, optimization of the OoC-platform was done by fabrication of the platform using Polydimethylsiloxane (PDMS).

It was shown that the OoC platform for Vascularized Organoids-on-a-Chip could effectively by fabricated using PDMS molding. This was achieved through both PDMS-PDMS and PDMS-glass bonding. Pluronic F127 hydrogels were shown to be a viable option to function as a transient barrier for Vascularized Organoids-on-a-Chip. Pluronic F127 hydrogels effectively blocked fluid flow through the barrier channel for seven days. To increase this time, di-acrylated Pluronic F127 was synthesizes. A degree of acrylation of 57% was achieved. This was shown to be insufficient to significantly increase the longevity of Pluronic F127 hydrogels.

Further research needs to be done to find the optimal synthesis and photo-polymerization conditions of di-acrylated Pluronic F127 hydrogels. Ideally, di-acrylated Pluronic F127 hydrogels exhibit a low degradation rate while maintaining the thermoreversible properties of Pluronic F127 hydrogels.

Mycelium based composites (MBC) have revolutionised the field of material production, where a living fungus is employed to overgrow and bind lignocellulosic substrate materials together. Their bio-based nature, low embodied energy, and biodegradability, mark their great potential to reduce the increasing pressure conventional materials put on the environment. Unfortunately, the material's applications are limited due to its low mechanical properties, that are equivalent to those of foams or natural fibre boards. Furthermore, where the material is primarily used and studied in its heat-treated non-living form, harnessing the biological power of the fungus shows to give the material self-healing and sensing capabilities. The required hydrolysed state is however shown to further decrease its mechanical properties, and yet hardly evaluated in literature. Especially the mechanics of the mycelium-lignocellulose interface are inadequately studied, and important to evaluate for a broadening of the living composite material's applications.

In this study we present the development of a double cantilever beam (DCB) test according to ASTM D5528, setup to quantify the interlaminar fracture toughness (G_I) of Ganoderma lucidum (G. lucidum) grown in between wood veneers. The data was evaluated using an analytical approach based on a decrease in the beams' compliance. The specimens were fabricated with the use of additive manufacturing, allowing precise control over the placement of the fungus and its provided nutrients. Its growth behaviour into the substrate was qualitatively assessed through optical microscopy and scanning electron microscopy (SEM), and its digestive ability on the surface by fourier-transform infrared spectroscopy (FTIR).

A mycelium-laden ink presented by Gantenbein et al. (2023) was reproduced with a 75% lower agar content to serve a stable source of mycelium on the DCB specimens [1]. A growth period between 3 and 4 weeks from the printed hydrogel was required for substantial mycelium-substrate binding, which stabilised after 4 weeks of growth. Furthermore, the provision of malt extract (ME) was required, but not needed to be higher than 5% of the ink's weight. The G_I was in these conditions reported to be 1.83 J/m² on hornbeam veneers, where a maximum value of 3.46 J/m² was reached. Variable growth generated substantially different mechanical properties, which resulted in the lower G_I of mycelium grown on beech and spruce samples, caused by the use of an older fungal inoculum of a different reference plate. A stronger binding on beech than spruce did suggest a more important role of the substrate chemistry than its density. The mycelium always showed cohesive failure, showing the low G_I to not result from poor substrate adhesion, but rather from the mechanics of the hyphae network developed. Microscopy and FTIR evaluations showed the ability of G. lucidum to digest the hornbeam's lignin. The full depths of hornbeam and beech veneer substrates with 5 and 3 mm thickness were colonised, where vessel elements served as the main pathway for the hyphae.

This study was, to the best of our knowledge, the first to isolate the binding behaviour of a living mycelium in a mode-I loading condition. It thereby provides valuable new insights in the field of living MBC, and contributes to the further development of this advanced, eco-friendly, and living material. The setup can now be utilised to study the binding behaviour of different fungi on substrates of varying chemistry and porosity. Furthermore, aiming to elucidate the use of additive manufacturing in the composite production, this study opened up pathways into controlling the composite's properties in the future.

[1] Silvan Gantenbein et al. “Three-dimensional printing of mycelium hydrogels into living complex materials”. In: Nature Materials 22.1 (2023), pp. 128–134.

Composite materials offer superior mechanical performance with lower weight than traditional materials. As a result, they are widely used in various industries, such as aerospace, automotive, construction, and sports. The composite industry is increasingly utilizing natural fibers and developing biodegradable composites in response to environmental sustainability concerns. Natural fibers have comparable physical and mechanical properties to glass fiber, making them suitable for use in the production of bio-composites. Despite this, natural fiber cannot fully replace glass fiber due to a variety of factors that influence the material's variable properties such as the type of fiber used, the conditions in which the fiber grows, the processing methods, and any modification of the fiber. Hence most of the research done on bio-composites has concentrated on using them in non-structural parts.

This project aims to develop and characterize a green and sustainable bio-composite system, to overcome existing application challenges. The constituent materials include a bio-resin extracted from seaweeds and Unidirectional Flax fibers as reinforcements to stiffen and strengthen for semi-structural applications. Although alginates have been studied in-depth for their biomedical applications, their potential as a bio-based matrix for biocomposites has not yet been explored.

In addition to the materials used in the composite preparation, the processing technique significantly impacts the final properties of the composite. Therefore, in the first half of the work, thorough research was conducted to study the constituent properties for their processing. The second half of the work defined a new approach to manufacturing bio-composites from natural constituents. The corresponding analysis useful for product design are thoroughly demonstrated in this thesis.

However, using natural fibers in composites and water alginate soluble matrices has three main concerns: the fiber/matrix interaction and their sensibility to moisture absorption and residual water within the composite structure. Their surfaces can be modified using physical and/or chemical methods to improve the bonding between fibers and matrix. In most studies cited in the literature, the chemical modifications employed are synthetic and toxic. It would be ideal if the chemicals used to modify natural fibers were bio-based and preserved the biodegradable nature of natural fibers.

The development of an optimized seven-step manufacturing approach is a key innovation for water removal, to enhancing fiber reinforcement and boosting overall composite performance, particularly in the use of flax fibers. This approach is notable for its novelty and challenge, as evidenced by the limited literature on the subject. It focuses on achieving sufficient impregnation by utilizing low water percentages in resin, specifically around 7\%, and applying appropriate consolidation pressure and temperatures. The most effective results were observed at 5 MPa and 95°C, which facilitated homogeneous plasticization and mouldability. Additionally, the method of wet/dry cycling, incorporating pre-soaking and heating, has proven beneficial in providing dimensional stability to flax fibers and limiting water absorption, further contributing to the technique's effectiveness.

Analytical techniques like microscopy and SEM reveal promising compatibility between components. No degradation of the bio-resin or the fibers relatable to the heat press was identified.

Finally, the research aimed to establish a meaningful relationship between the critical process variables and the properties of the bio-composite, with the ultimate goal of optimizing the production process and enhancing the quality of the final product by varying the fiber volume fraction within the range of 41-47\%.

The maximum tensile and flexural strengths achieved were 219MPa and 56Mpa, respectively. The elastic tensile and bending moduli in the composites were approximately 6.64GPa and 1.83GPa, respectively.

However, the observed properties fell below the predicted values for the biocomposite system, which were calculated using the rule-of-mixtures and Halpin-Tsai methods. Nonetheless, the experimental data confirm that these biocomposites can be used as secondary structural elements. The observed discrepancy was due to the presence of huge voids further leading to poor adhesion.

Nanopores are narrow channels in cell membranes that control the passage of small molecules. In recent years, they have been repurposed for diverse applications, including single molecule sensing and drug delivery. Due to the small diameters of conventional protein-based, current research efforts are directed to designing nanopores from other materials to achieve larger diameters. DNA origami has emerged as a promising method for the precise fabrication of nanoscale structures. Using advances in structurally-adaptable DNA origami nanotechnology, here we investigate DNA-based nanoactuators with size-adjustable diameters, which can potentially reach diameters of up to 100 nm, that could be used for macromolecules translocation. The focus of this thesis is the study of the mechanical states of these nanoactuators, which can be triggered to change shape in response to a specific molecular trigger. Given the nanoscopic dimensions of our actuators, we select DNA PAINT for imaging, which is a type of super resolution technique, that can achieve a resolution of 10 nm, beating the optical diffraction limit (~200 nm) of conventional light microscopy. DNA PAINT experiments are performed in combination with total internal reflection fluorescence (TIRF) microscopy to characterize the behavior of DNA origami nanopores in physiological conditions. By testing various parameters sample related and imaging software ones we identify optimal conditions suggesting 5mM Mg^(2+) ions in buffer solution and 1nM DNA nanopores. Laser power (40mW), exposure time (400ms), waiting time between frames (300ms), and image duration (50s) are optimized, resulting in the expected fluorescent blinking behavior which enables us to perform single-molecule localization. The individual corners of the nanopores were, however, not resolved with this technique due to limitations in the resolution of the imaging system. We recommend that future work could exploit the even better resolution of a modified DNA PAINT approach i.e. Exchange PAINT, which has been proven to achieve Angstrom level resolution for imaging of DNA nanostructures.

Epoxy resins are one of the most relevant and widely used thermosets in the market covering a wide range of applications. Industries are being forced to quickly transition towards sustainable alternatives due to the pressure from emerging environmental concerns, the depletion of petrochemical supplies, and compliance with environmental legislation. Since the primary component of epoxy resins is derived from petroleum (Bisphenol A (BPA)), companies like Westlake Epoxy have joined the search for innovative, environmentally friendly solutions. Many bio-based substitutes have surfaced in recent years, in efforts to eliminate or reduce the quantity of BPA in epoxy resins. Attention has been focused on lignin biomass as a viable feedstock in the manufacturing of these thermosets because of its large production volume and some structural characteristics.

This study addresses the synthesis of novel lignin-based epoxy resins and the evaluation of their potential application in the field of coatings and composites. For this research, different sources of technical Kraft lignin were employed. Since technical lignin is not very reactive due to the large molecular weight polymers, a Confidential Fractionation process has been developed. For its synthesis, both small- and large-scale glycidation processes were successfully implemented. To understand the chemical structure of lignin and its corresponding resins, different analytical techniques were used such as Gas Chromatography (GC), titrations, Nuclear Magnetic Resonance (NMR), Fourier-Transform Infrared Spectroscopy (FT-IR) and Gel Permeation Chromatography (GPC). Additionally, for the development and characterisation of coatings and composites, a variety of material testing techniques were employed, namely Differential Scanning Calorimetry (DSC), Dynamical Mechanical Analysis (DMA), Thermogravimetric Analysis (TGA), Interlaminar Shear strength (ILSS), Impact testing, Pendulum hardness, among many others.

Experimental results showed an average fractionation yield of 50-60% of technical Kraft lignin using the Confidential Fractionation process. Compositional differences in the fractionated lignin substrates studied via NMR analysis, predict some differences in the reactivity of these substrates towards glycidation, which is supported by different Epoxy Group Content (EGC) of the corresponding epoxy resins. The EGC of the lignin-based epoxy resin is significantly lower than that of the reference resin due to the presence of bulky moieties that hinder the reactivity of active sites. While lignin-based coatings exhibit comparable performance in hardness and direct impact resistance, however, its high viscosity and stiffness results detrimental in other areas. On the other hand, this high viscosity is a major challenge in the processes of prepreg laminates leading to poor adhesion of the fibres to the matrix, which has a negative effect when it comes to mechanical performance. However, adding lignin to epoxy resins has proved to improve the thermal stability of these materials.