Accurate measurement of blood flow in deep tissue is essential for diagnosing and monitoring a wide range of clinical conditions, yet current imaging methods are often invasive, limited to snapshots, or impractical for continuous bedside use. Diffuse correlation spectroscopy (DCS) offers a non-invasive optical alternative, measuring blood flow dynamics through temporal fluctuations in scattered light. However, modelling DCS signals remains computationally challenging, particularly when accounting for structured flow and tissue complexity.
This thesis investigates a coupled simulation framework that integrates particle dynamics from COMSOL with optical propagation computed via a modified Born series solver (WaveSim). The framework was used to test three validation cases: temperature-dependent Brownian motion, laminar flow, and parameter extraction through exponential fitting of the autocorrelation function.
The results demonstrate that the framework captures the qualitative behaviour of DCS. Brownian motion produced linear mean squared displacement (MSD) curves, with faster optical decorrelation at higher temperatures, while laminar flow introduced quadratic MSD growth and accelerated decay. However, quantitative agreement with theoretical scaling was not achieved. A key limitation was identified as a pixel-quantisation effect: particle displacements per frame were typically far smaller than the 0.2 μm WaveSim pixel size, rendering most motion invisible to the solver. This suppressed decorrelation, distorted temperature and flow scaling, and prevented unbiased parameter extraction. Additional constraints included limited statistical averaging, absence of phase tracking, reliance on decay rates without correlation diffusion equation (CDE) modelling, and high computational costs.
The findings confirm that the COMSOL–Born framework provides proof of concept for simulating DCS but requires significant refinement for quantitative accuracy. Future work should focus on subpixel rendering, improved temporal sampling, integration of CDE solutions, and domain decomposition. With these improvements, the framework has the potential to advance real-time, non-invasive monitoring of blood flow in clinical settings. i

Miniaturizing optical systems is necessary and useful for many different applications, such as cameras and optical sensors. Recent breakthroughs in metalenses have enabled ultra-thin optical components, driving efforts to reduce the free space propagation distances between them. This can be done using devices called spaceplates, which mimic the phase response of free space propagation within a shorter relative distance. This thesis investigates the properties of theoretical spaceplates comprised of multilayer thin film structures, designed through optimization. It explores the limits of achievable effective distances by stacking devices, ultimately demonstrating a theoretical effective distance of 23.3 mm for an NA of 0.087 and 1550 nm wavelength. It also finds manufacturing errors have a significant influence on this metric, reducing achievable effective distances to millimeter scales. Lastly, it explores combining the spaceplate function with angular stray light filtering to achieve multifunctional designs, with promising results.

Despite advances in astronomy, much of the universe remains hidden behind gas and dust clouds that absorb optical radiation, making it undetectable by conventional telescopes. Far-Infrared (FIR) radiation is capable of propagating through these clouds, and offers a solution for observing these obscured interstellar regions. However, the sensitivity of existing detector systems is insufficient to detect FIR radiation effectively. This thesis focuses on the development of highly sensitive detectors based on Microwave Kinetic Inductance Detectors (MKIDs) that meet the sensitivity requirement for use in future space missions, specifically the NASA led POEMM and PRIMA missions, covering a frequency range from approximately 1.5 THz to 12 THz.

While detectors have been developed previously covering the upper band of this frequency range at 6.98 THz and 12 THz, the lower band remains uncovered. Therefore, lens-absorber coupled MKIDs designed to operate at 1.5 THz are presented, with their performance analysed using models based on the Geometrical Optics-Fourier Optics (GOFO) technique in combination with a Floquet wave approach for periodic absorbers. Additionally, the design methodology of MKIDs to operate at specific readout frequencies is discussed. Absorber coupled MKIDs are limited to lower resonance frequencies with respect to comparable antenna based MKIDs, which offer advantages for space-based missions due to reduced power consumption, but do present challenges for readout systems operating at higher frequencies. In this thesis, two lens-absorber coupled MKID designs were developed and are currently being fabricated as candidates to experimentally demonstrate highly sensitive detector arrays operating at 1.5 THz.

The imaging spectrometers in the POEMM and PRIMA missions require a dispersive element to separate different wavelengths of the incoming radiation. The dispersive element envisioned for these missions, the Virtually Imaged Phased Array (VIPA), suffers from non-idealities, causing phase aberrations in the transmitted field, and part of the power transmitting towards unwanted propagation directions, which can degrade instrument performance. This thesis presents and analyses optimisation techniques to mitigate these effects, thereby enhancing the overall efficiency and degrees of freedom for designing the full instrument.

Furthermore, absorbers, unlike antenna-based devices, are multi-mode detectors. Understanding how absorbers couple to higher-order modes is crucial for optimising their performance. This thesis introduces and validates a model based on a novel experimental technique, Energy Absorption Interferometry (EAI), to extract a modal description of detectors. In the future steps related to the POEMM mission, the findings from this initial investigation into multi-mode absorbers will be used to gain insight and explore possible improvement routes in the coupling of these detectors to complex optical systems.

To support the integration of Acousto-Optic Tunable Filters (AOTFs) in optical systems and lay the groundwork for further research, this report presents the development and validation of an analytical model for a noncollinear AOTF based on tellurium dioxide (TeO2). The AOTFs are compact solid-state devices that filter desired optical wavelengths by applying an appropriate RF signal. Their compactness and quick tunability make them particularly appealing for Earth observation missions, where an AOTF can be integrated into small platforms like CubeSats.

However, there is a significant gap in the availability of comprehensive optical AOTF simulations that can predict the behaviour of AOTFs, and specify the momentum-matching frequencies required for the highest diffraction efficiency (DE) to occur. This report addresses that gap by developing a detailed three-dimensional (3D) analytical model for the non-collinear AOTFs based on TeO2, the most commercially available and widely used AOTF configuration. The analytical model, developed in this report, aims to facilitate the design and optimization of AOTFs for optical systems used in various fields, particularly in space-based instruments.

The core of the AOTF’s analytical model can be broken down into three main stages: the entrance facet, the acoustic field, and the exit facet. The interaction of light with these three stages is simulated by rays, the direction of which is determined by the Directional Cosine Matrices (DCMs). The model performs calculations to describe the path of incoming rays as they enter, propagate through, and exit the AOTF crystal. Special attention is given to simulating the Acousto-Optic (AO) interaction within the crystal, where a diffracted light is produced. Furthermore, the model calculates the momentum-matching frequency and outputs the propagation
of a newly created diffracted light through the AO interaction.

The developed model is adapted to operate for both incident polarisation types, ordinary and extraordinary. Furthermore, the model can simulating the AOTF’s behaviour as it is rotated, allowing further versatility of AOTF’s placement in the optical design. The model, as well as the adaptations, were first verified with the data from the Voloshinov et al. paper, where it accurately predicted both the separation angles and the momentum-matching frequencies. Further verification was performed with known AOTF parameters at various optical wavelengths with the help of an experiment performed at Université Polytechnique Hauts-de-France (UPHF).

Furthermore, the model was validated through diffraction testing, where it successfully simulated the AOTF’s behaviour, predicting both diffracted and undiffracted ray angles with an accuracy of 0.1 degrees. Testing was conducted at various rotational angles and for both incident polarisation types, with the model’s predictions closely matching the experimental data. Based on the testing, it was possible to determine the frequency-matching method used in characterising the essential AOTF angles that dictate the AOTF’s behaviour.

The analytical model was further enhanced by incorporating an optimization algorithm, which automates the characterization of key AOTF variables for newly acquired devices. The algorithm characterises the crystallographic axis angle, tilt angle, and facet inclination angles. These parameters are typically not provided by manufacturers, leaving the AOTF’s behaviour largely unknown. However, by characterising these variables with the model created, it becomes possible to extrapolate the AOTF’s performance for any incident optical wavelength within the visible spectrum.

Bio-imaging plays an essential role in life sciences and medicine. Recently, structured illumination has emerged as a promising super-resolution technique. However, in the case of thick scattering media, the benefits of structured illumination can be significantly reduced compared to conventional illumination methods, resulting in significant degradation of imaging quality. Therefore, the question of dealing with the challenges posed by structured illumination in scattering media has become a topic of considerable focus. In this thesis, an experimental setup aimed at achieving super-resolution imaging using structured illumination is developed. The factors influencing the imaging process are systematically analyzed. At the same time, machine learning methods for recovering structured illumination patterns propagated through scattering media are explored. Overall, this research tackles the challenge of improving super-resolution imaging through scattering medium thereby contributing to the development of biological and medical imaging technologies.

In a world increasingly dominated by technological advancements, the demand for high-quality microphones has never been more present. Seamless speech recognition and the development of userfriendly hearing aids remain significant challenges. State-of-the-art micro-electromechanical system (MEMS) microphones are reaching their bottlenecks in terms of thermo-acoustic noise, caused by the acoustic resistance of the parallel plate capacitor. This constrains the achievable signal-to-noise ratio (SNR). This thesis presents a novel solution to address these challenges through the application of silicon photonics technology in the development of a silicon photonic microphone. Silicon photonics is a technology that uses silicon as an optical medium to create photonic systems with sub-micrometre precision, which can be used to create ultra-sensitive sensing devices. The optical sensors are fabricated on standard silicon-on-insulator (SOI) wafers, allowing for seamless integration with the precise and cost-effective complementary metal-oxide-semiconductor (CMOS) process. The optomechanical
sensitivity of the proposed microphone is derived for three different cladding materials that could be deposited on the wafer in the fabrication process. The thermal acoustic noise of the microphone is quantified. As the integrated photonic circuit does not require a backplate the design potentially reduces the thermal acoustic noise of current microphones by 44 %. The optimized design for the laboratory setup that is considered for this thesis can theoretically result in an SNR of 73.1 dB, which is roughly 5 dB more than the current state-of-the-art microphone technology.

The research objective of this research is to develop a measurement method that can measure thin film thicknesses through a multilayer that consists of both surrounding thick layers and in between thin films. An optical non-contact measurement method is researched and developed to non-destructively measure the thickness of a liquid thin film, which is situated between other layers. The measurement method used in this research is called spectral reflectance. The method works by analyzing the reflectance spectrum from a light beam which is directed perpendicularly and with a wide range of wavelengths on the surface of the layer. The reflectance spectrum that is measured with a spectrometer includes oscillations that result from the interference of light that reflects at the different interfaces in the multilayer. The oscillation contains frequency content which is used to determine the thickness of the layer. This research shows that the spectral reflectance technique can be used to measure the thickness of a stack of thin films with the condition that the thin films are all coherent. It is possible to determine the film thickness of a stack coherent thin films, which are surrounded by incoherently thick layers. The outer layers can be assumed to be incoherently thick based on a combination of factors such as the layer thickness of the thick layer, the measured wavelength range and the resolution of the spectrometer.

Shape changing active metamaterial could form the structural backbone of an object as well as deliver the actuation. The integration of these two functions saves design space and allows for creative topologies. The literature study of this thesis investigated smart material actuator solutions that could be used to enable such active metamaterials, covering PVDF, dielectric elastomers, IPMC, conducting polymer, carbon nanotubes and piezoelectric ceramics. It is found that dielectric elastomers achieve high strains, low stress and need high driving voltages. Conducting polymers are able to deliver both high stress and high strain, but consume relatively much power. If power consumption is a priority, Electronic EAPs are preferred. PVDF does not excel on stress or strain, but is an overall good performer. The outlook of realizing active metamaterials via integration of actuation paves the way for non-rigid body deformations and broadens the view on potential applications. At the moment such a system cannot be realized due to the lack of appropriate designs and manufacturing methods. The objectives of this report are (1) the employment of smart materials to make metamaterials active, (2) proposing a method of how to realize this using production materials and (3) employing these methods to build a small metamaterial demonstrator that functions both as the actuator and the structure. In this work this was done by designing and constructing a tube shaped metamaterial demonstrator of a high precision positioning system. The 3D geometry of the metamaterial was built by layering planar pre-fabricated structures which use smart material for actuation. The design of the unit cells can be implemented in metamaterial of any shape and allows for miniaturization, which extends its applicability. The metamaterial was capable of vertical displacements. The constructed metamaterial tube was able to bend itself. Measured maximum amplitudes of a single layer, and the three layered stack were respectively 4.60 μm and 6.91 μm. Roll movement of the top layer of the stack was achieved with a lowest point of -0.13 μm and a highest point of 8.49 μm. The system showed that smart materials are a suitable choice to make metamaterial active, and that active metamaterial could be produced using production material. The planar approach for design and fabrication, provides a relatively simple and fast method for building metamaterial in general.

There is an ever-increasing demand for high data transfer rates. Laser satellite communication is a promising technology which offers high data rates and more secure links than the mature radio frequency (RF) communication. To make a laser communication terminal market viable it must be low size, weight and power (SWaP). The telescope drives the volume of the terminal. Making the telescope more compact with high magnification imposes stricter tolerances. A solution to alleviate these tolerances is to use a refocusing mechanism (RFM) to align the telescope in space after launch. In this project, a refocusing system is designed. This comprises of making system level choices like where to place the mechanism, how to close the loop and how to use the onboard detectors. All these choices lead to the requirements for the RFM. Further, a mechanism is designed that fulfills the requirements. In addition, mechanical and thermal FEM simulations are carried out to show that the RFM survives launch and can work in the challenging thermal environment.

The central nervous system has a very limited capacity to regenerate damaged tissue. Therefore, regeneration strategies focus on transplantation of neural stem cells or differentiated neural cells. In order to make such a treatment effective, it is important to understand the mechanisms that enable cell differentiation. It is well known that besides biochemical cues, also mechanical and geometric properties of the cell environment, such as topography, curvature and stiffness, can influence the process, which has been studied mostly in 2D. In order to conduct relevant cell studies in vitro, it is therefore important to mimic the 3D structure of the in-vivo cell environment. Many different approaches have been adopted to create scaffolds for neuronal cells, such as freeze-drying, electrospinning and stereolitography. The main drawbacks of these methods are the limited resolution and the constraints in terms of achievable geometries. Two-photon polymerization overcomes these problems by using a laser to polymerize a photosensitive material in extremely confined volumes, achieving a submicrometric resolution. In this study, we fabricated 3D microscaffolds made of an acrylate polymer called IP-Dip by employing two-photon polymerization in order to study the effect of curved versus straight lattice geometries on the differentiation of mouse embryonic stem cells into neural progenitor cells. First, feasibility studies were carried out with HeLa cancer cells and the effect of curvature on these cells was investigated on 2.5D structures. We established a workflow for conducting these experiments from the fabrication up until the analysis. By employing confocal imaging, image stacks were obtained and then analysed to obtain the volumetric cell occupancy of the scaffolds and identify the location of the cells within the scaffolds. We concluded that mESCs could successfully grow and differentiate within the 3D scaffolds without a specific preference for a curved over a straight lattice structure.

Spinal fusion is a surgical treatment involving stiffening parts of the spinal column to eliminate any relative motion and improve spine stability. A critical part of spinal fusion surgery is the placement of pedicle screws because it is highly complex and can damage the vascular structures and nerves near the vertebrae. To prevent complications, a new anchoring method is developed that strengthens screw contact by following the curved trajectory of the dense cortical shell while avoiding a cortical breach. Diffuse reflectance spectroscopy (DRS) is a technique that could be used in a bone drill to obtain real-time information about the location of the drill within the vertebra. In order to drill the correct trajectory, an optical probe using DRS should determine the parallel closeness of cortical bone to the drill tip. To show the potential of this novel technology for improving spinal fusion surgery, this master thesis introduces and validates a flexible sideways-looking probe using DRS to identify the proximity of cortical bone when measuring along the cortical shell of a vertebra.

In this study, the ideal optical design to detect the proximity of cortical bone is investigated by looking into the effect of fiber angulation on the photon propagation using Monte Carlo simulations and phantom experiments. A conceptual design was created based on the ideal optical design combined with the mechanical requirements to make the probe insertable into a vertebra. As a proof of concept, a prototype was developed and tested on a bone-mimicking phantom and porcine vertebrae.

The conceptual design comprises a flexible needle with two optical fibers attached to a rigid tip with a diameter of 2.9 mm. Two mirrors are positioned in the rigid tip, emitting light 45\degree off-axis and collecting light 90\degree off-axis with a source-detector separation of 2.1 mm. These light directions were chosen because they optimize the reflectance spectrum difference between cancellous and cortical bone due to a longer path length, making detecting cortical bone closeness easier. A prototype was made that demonstrates that the probe can detect the parallel proximity of cortical bone at a depth up to 1.5 mm in an ideal phantom setting. The prototype can distinguish between pure cancellous and cortical bone in porcine vertebrae. Additionally, the prototype can also be inserted into the pedicles and bent along the cortical wall of a vertebra. These positive findings show that the flexible sideways-looking probe created in this study can potentially improve spinal fusion surgery by enabling an increase in cortical bone contact without perforating it. Although proof of concept has been provided, it is essential to improve the design for safety and usability and improve tissue type identification accuracy before continuing to clinical trials.

A research gap exists in a targeted drug delivery into the brain with an implant placed on the outer surface of the cerebral cortex. If an implant with spatial control that can release drugs to a target location can be developed, it will provide efficient treatment opportunities for a variety of brain disorders such as strokes. One of the questions in realizing this implant is how to activate the drug release mechanism. Light is a promising activation stimulus due to its spatial precision and flexibility in the optical path. This thesis is a feasibility study into carrying light inside such a brain implant using a photonic crystal waveguide. Such a device must be soft and maintain its functionality during the mechanical bending imposed on the implant by the geometry and movement of the brain. A flexible 2D photonic crystal is simulated using COMSOL Multiphysics with the goal of designing a waveguide that functions with infrared light. The dispersion diagram of the photonic crystal is plotted to design for a bandgap at the operating wavelength. The transmission through a linear waveguide is calculated for the deformed state of the implant in mechanical bending, which is modeled as a 2D strain. A metallo-photonic crystal with photoresist nanopillars coated with a gold thin film and embedded in a flexible PDMS matrix is selected as the prototype for fabrication. The nanopillar arrays that form the photonic crystal waveguide are printed using two-photon polymerization (2PP), deposited with gold then transferred into photosensitive PDMS by drop casting. For characterization, a tapered rib waveguide is designed for light coupling and an optical end-fire test setup is built for transmission measurements on the fabricated device.

With climate change being a prime source of concern around the world, air pollution is a topic that requires special attention. Therefore, it is of utmost importance to track and measure the emissions in our environment for detecting the sources and understating the climate change so as to figure out possible solutions. Despite ongoing development, the current LEO and GEO satellite instruments have a long prolonged global survey, revealing the pollution trends at a broad scale, but there is still a lack of high-resolution data to pinpoint pollution sources.

For this, John Hopkins University (Applied physics lab) and NASA are now developing a new earth atmospheric monitoring mission called Compact Hyperspectral Air Pollution Sensor (CHAPS) to address it at a local scale. Presently, TNO is carrying out the design study for this system by employing both freeform optics and additive manufactured mechanics. The mission objective is to perform targeted local measurements of the atmosphere on a daily basis by providing high spatial and temporal resolution possible in UV-VIS wavelength range.

In order to characterize, quantify, and monitor emissions from urban areas, power plants, and other anthropogenic activities, it is important to collect accurate and precise data and calibrate the optical instrument. But the data often received from the sensor is not reliable due to the operational and the non-operational conditions leading to cross-sensitivity, change in the trajectory, and optomechanical errors. For this, an on-board calibration system is developed to perform continuous calibration of the science product, that is compatible with both the instrument and the satellite platform and is robust to the variable operating conditions. This requires a stable system that achieves a good performance that is insensitive to thermal and mechanical disturbances, in order to meet the strict specifications.

As opposed to conventional methods, additive manufacturing, enables new possibilities for developing Optomechanical structures because of the layer-wise manufacturing technique. This manufacturing process is widely touted as a foundation for the next industrial revolution as it offers profound advantages like shorter lead time, lower wastage of materials, and higher geometric complexity that can be useful for multi-functional and multi-material structures. It can also facilitate good strength, significant mass reduction, and better dimensional homogeneity and stability. At the same time, additive manufacturing is not an easy process and requires new design strategies and solutions for overcoming the existing constraints.

The prime research objective is to investigate the optomechanical design of the spectral calibration module applying a kinematic approach. The second research objective is to investigate design and the potential improvements when applying additive manufacturing. The present case study demonstrates and evaluates the preliminary phase of the calibration module design study, thus providing the key ingredients for the realisation of the full system.

BACKGROUND: Ovarian cancer is the number eight cause of cancer-related mortality in women around the world and has an incidence of more than 295 000 and mortality of almost 158 000. The most important prognostic factor for the survival of advanced-stage ovarian cancer is the complete resection of all microscopic tumour tissue during cytoreductive surgery. Still, even after complete CRS and removal of all visible and palpable tumours, more than two-thirds of women with advanced-stage ovarian cancer experience recurrence due to microscopic residual tumour. Therefore, an intraoperative visualisation technique is of great importance to detect these microscopic tumours. In this pilot study, the feasibility of NIR hyperspectral imaging for the detection of malignant ovarian cancer metastases was evaluated ex vivo. METHOD: Patients with suspected primary ovarian cancer planned for cytoreductive surgery were enrolled in the study. Hyperspectral images from the resected tissue were acquired in the wavelength range of 665-975 nm. All hyperspectral data was preprocessed by image calibration, min-max normalisation and noise filtering. The the most important features were selected before implementing the hyperspectral data in the classifier. The linear SVM, RBF SVM, and a k-NN classifier were used to discriminate malignant ovarian tissue from the surrounding tissue. The performance of the classifier was evaluated by leave-one-out cross-validation. RESULTS: Ten patients were included in the study. The linear SVM classifiers had the highest performance with a sensitivity of 0.81, a specificity of 0.75, AUC of 0.83 and MCC of 0.41. Thereafter came the RBF SVM classifier followed by the k-NN classifier. CONCLUSION: This pilot study shows that hyperspectral imaging with the use of a linear SVM classifier is a promising technique to discriminate malignant ovarian tissue from the surrounding tissue. Hyperspectral imaging can scan a whole area, is fast, non-contact, non-invasive and can be used inside the operation room. However, before HSI can be implemented in real practice, further validation is required in vivo and technical enhancements need to be made such as enlarging the training data set, evaluate the SWIR wavelength range, include a registration algorithm which accounts for elastic deformation of the tissue, evaluate several feature selection methods, and compare other classifiers.

The manufacturer of an electron beam lithography machine pushes a better understanding and higher performance of the optical column to provide a better product with each iteration. At the heart of the column is the source of electrons: the gun lens. It holds the field emitter from which the electrons originate and accelerates the beam to a first crossover. The main work in this thesis was concerned with development of a new and better gun lens design. Consideration of several physical phenomena is required in order for the gun lens to be more robust and with a more stable beam. It was found that the heating transient plays a large role in the operation of the gun lens. By defining the requirements clearly including by ray-tracing the optical geometry to find optical sensitivities, the main challenges of the project became evident. A new concept design is presented where the heat transport inside the gun lens is improved and thermal drift is greatly diminished. By using the ceramic insulators as flexures the short- and long-term stability of the lenses are improved and the thermal transient settling time is reduced from 26 hours to below 6 hours. By opening up the geometry inside the gun lens the local vacuum at the emitter is much better, which increases its lifetime. The electrostatic fields are made much more robust by burying the triple junction, which required using a new insulator shape. The final result is a gun lens concept design which improves in all aspects while remaining simple in construction.

Introduction. In spinal surgery, the misplacement of spinal screws is a problem that causes (severe) pain, bleedings or even paralysis [2]. Screw misplacements are common as navigating in the spine is difficult due to the small vertebral dimensions and a lack of anatomical landmarks [3] [4]. In order to improve the navigational support of spine surgeons, this research focuses on the development of an optical sensing diffuse reflectance spectroscopy (DRS) surgical drill that identifies bone tissue boundaries. The developed drill concept introduces a stagnant optical fiber-equipped probe into a cannulated orthopaedic drill. To verify the clinical applicability of the developed system, the accuracy of the optical tissue boundary detection has been analysed under different tissue penetration speeds, as well as the axial drilling force increases due to the introduction of a stagnant probe into a drill.
Results. When increasing the drilling feed rate in the optical phantom, the drill overshoot (the difference between the DRS-derived tissue boundary location identification and the actual location of the phantom boundary) shows a larger spread. The maximum feed rate at which no overshoot takes place is 0,5mm/s. Increasing the sampling frequency –especially decreasing the inactive period between the measurements– can improve this.
None of the K-wire equipped drills can penetrate the used Sawbones® cortical bone phantom. The axial peak feed forces occurring in the Sawbones® cancellous bone phantom while using a regular 2,7mmØ orthopaedic drill is 38,2N. When using the 2,7mmØ orthopaedic drill with a 1,6mmØ K-wire, a peak of 57,6N is observed. Because the data from drilling in the Sawbones® cancellous bone is not normally distributed, a benchmark experiment on cheese is analysed. On average, the introduction of a K-wire increases the required drilling forces by a 296% (roughly a factor 3). Among the different feed rates and drill types, the force increase of introducing a stagnant K-wire varies between 16% and 575%.
Conclusion. To prevent orthopaedic screws from breaching the bone surface (an overshoot of 0mm) in spinal surgery, the established feed rate speed limit of 0,5mm/s is too low. To meet the observed feed rates applied by surgeons of up to 5mm/s, it is of interest to reduce the DRS sampling time – the inactive period between two measurements in particular. The feed force increase of approximately a factor 3 can be regarded as a challenge for surgeons, who indicated that they preferred feed forces to be kept low. Further testing on real (cadaveric) vertebrae can more give information about the DRS drill’s optical performance in pedicles, and whether the identified feed force increase proves to be problematic for clinical applications.

In spinal surgery, the misplacement of spinal screws is a common problem that causes (severe) pain, bleedings or even paralysis [1] [2] [3]. In order to improve the navigational support of spine surgeons, this research focuses on the development of an optical sensing diffuse reflectance spectroscopy (DRS) orthopaedic drill that identifies bone tissue boundaries, based on fat fraction. The developed drill concept introduces a stagnant optical fiber-equipped probe into a cannulated orthopaedic drill. To verify the clinical applicability of the developed system, the accuracy of the optical tissue boundary detection has been analysed under different tissue penetration speeds, as well as the axial drilling force increases due to the introduction of a stagnant probe into a cannulated drill. The maximum feed rate at which the drill consistently detects the tissue boundary before breaching it, is 0,5mm/s. The force increase due to the introduction of a stagnant probe is a factor 2,96 on average and varies widely between different feed rates and probe diameters (a factor 1,15–5,75). The established feed rate speed limit of 0,5mm/s is lower than drilling feed rates of up to 5mm/s, observed in the operation room. Increasing the sampling frequency –especially decreasing the inactive period between the measurements– is required. The feed force increase of approximately a factor 3 can be regarded as a challenge for surgeons, who indicated that they preferred feed forces to be kept low.

Large scale, highly sensitive and specific diagnostic tools are needed to eliminate the transmission of schistosomiasis. This report expands upon the novel approach from M. Hoeboer and P.M. Nijman. Their Smart Optical Diagnostic Of Schistosomiasis device (SODOS), combining the principles of flow cytometry and digital holography, was able to detect schistosomiasis haematobium eggs in a 10 ml urine sample. However the mechanical complexity made it difficult to control the flow and more than 650 frames needed to be processed for each sample. The reason for this was the small flow cell volume examined within each frame. This report shows it is possible to increase the volume while maintaining the required resolution for accurate diagnosis. The size of the volume is limited by the sensor’s pixel pitch, the sensor area, the shutter time of the sensor, the thickness of the volume, the density of particles and to a lesser extent the distance of the volume to the sensor and the wavelength of the source. The density of particles in combination with the thickness of the volume proved to be
the main limiting factors. With to many particles the scattered light causes a cloudy, speckle pattern on the sensor, which does not give the desired resolution upon reconstruction. By using a 24MP APS­C CMOS colour sensor, present in the Canon EOS M50 camera, in combination with a larger volume it was possible to reconstruct eggs throughout 1.5 ml of urine using a single frame, decreasing the total required number of frames to 7. The volume thickness was 5 mm. Increasing the thickness to analyse the required 10 ml of urine in a single frame was not feasible due to scattering. However when
immersing the eggs in a Phosphate­buffered saline solution a 14 ml volume, with a thickness of 43 mm, could be analysed successfully, showing the possibilities of implementing the technique in other fields as well. The Fraunhofer particle field holography theory proved to be a valid model when making predictions regarding the resolution throughout the volume as well as providing information on the axial position of the particles.

We have set out to develop a drone, based on the existing Delftacopter, capable of soil monitoring via LiDAR remote sensing. The battery was to be replaced by a fuel cell system in order to extend the range threefold to 180km. Unfortunately, the ultimate design is likely unfeasible. Agriculture requires healthy soil and monitoring soil health is fundamental to its maintenance. Soil organic carbon in particular provides energy to the soil’s microorganisms, and is beneficial to water and nutrient retention. In addition, storing carbon in the soil is a form of carbon sequestration, which has become interesting due to the rising levels of carbon dioxide in our atmosphere. Monitoring soil organic carbon is therefore the goal of the drone design. The fuel cell system is a 650Whydrogen fuel cell by Intelligent Energy with a mass of 1290 g, which will be replacing the battery in the base design. Fuel tanks that were considered suitable are the 450 g, 0.5 L, 500 bar and 1350 g, 3 L, 300 bar fuel tanks by Meyer. It was found that one 1350 g and two 450 g fuel tanks were necessary to achieve the desired range of 180 km. However, after more careful drag estimates, this configuration turns out to be too heavy. 4 450 g fuel tanks remains feasible. Results below are based on this amount of fuel tanks. The incorporated LiDAR sensor is one by Velodyne, namely the Puck LITE, with a specified range of 100 m. The LiDAR sensor has a firing cycle of 55.296 &s, almost 20 kHz. Based on previous studies that used LiDAR to measure soil organic carbon, it has been established that a density of 5 data points per square meter is required. Fromour LiDAR parameters it turns out that the optimal flight altitude is 27.5mabove the surface that is to be measured, with a rotation rate of 10 Hz for the LiDAR sensor, when flying at a speed of 20ms¡1. With a flight distance of roughly 116km at 22.5ms¡1 (111km at 20ms¡1), an area of 21.8km2 per flight can be scanned. 1

EasyScan is a scanning system, which images the retina. The condition of the retina can help identify various diseases, such as glaucoma, diabetic retinopathy, cataract, macular degeneration and others. It is a commercially successful device that has sold thousands of units worldwide. However, the scanner is facing lifetime issues, as the scanner mirrors will become obsolete in the foreseeable future. Possible ways of improving the optical system by reducing the required scan amplitude were investigated. Optical tests with fine pitch lenticular lenses, diffractive optical elements, and linear diffuser were conducted. No optical improvement was achieved; therefore, the scanner design was based on the functional requirements of the original system. Actuation methods and guiding mechanisms for low cost, low volume applications were studied. The proposed design for both the low frequency (LF) and high frequency (HF) scanners is a compact reluctance force actuated scanner mirror. However, design issues for the LF scanner guiding mechanism were encountered, that could not be solved in time. Nonetheless, a prototype of the HF scanner was finalized and managed to achieve the required $\pm$\SI{3}{\milli\radian} amplitude at a frequency of \SI{4650}{\hertz}. The scanner was validated on an actual EasyScan optical module. However, reliability issues still need to be solved before making the scanner production ready, for which possible solutions are discussed.