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 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.

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.

The investigation of the interaction between lasers and brain tissue holds significant theoretical and practical significance in the field of brain physiology studies. A two-dimensional finite element-based simulation model was constructed using the commercial finite element simulation software COMSOL Multiphysics to investigate the propagation of light and photon correlation in tissues. The simulations included static and dynamic conditions of light propagation in tissue. In both cases this diffuse light propagation itself was studied along with photon correlation using the solution of the diffusion equation. Subsequently, the obtained simulation results are assessed and summarized by considering the outcomes of data fitting. The findings indicate that the accuracy of simulating light propagation is higher for larger sizes, although satisfactory results can be achieved for correlation propagation simulations in the small size range. The simulation results remain unaffected by the refinement of the mesh, provided that the fundamental criteria for mesh size are satisfied.

To further improve the light management and optical performance of solar cells, research into nano-textured interfaces has led to a need for a fast and accurate wave optics model. Currently, within the PVMD group at the TU Delft an optical solar cell simulation tool, GenPro4, is being developed to allow for the quick optimization and analysis of solar cell designs. However, the implemented wave optics model has limited accuracy and thus an alternative model is sought. In this thesis, we researched several rigorous wave optics simulation methods such as: finite element method, finite difference time domain, transfer matrix method, and rigorous coupled wave analysis. Based on three decision criteria (speed, accuracy, and compatibility) the choice of implementing rigorous coupled wave analysis (RCWA) was made. Besides the standard RCWA formulations, a few improvements were made. S-matrices were used to increase speed and memory efficiency of the program. Furthermore, calculation of the local E-field allowed for the determination of absorption per material in our cell. Lastly, an angular intensity distribution, known as scatter matrix, was produced as output to allow for the full integration with GenPro4. We validated our new model by comparing results of a nano-textured GICS solar cell with previously conducted finite element method (FEM) simulations. Over a large wavelength range our model showed good agreement with the FEM data. However, slight inaccuracies were observed at longer wavelengths (>1000 nm) as simulation of the metal back reflector became infeasible. Highly absorbing materials, such as metals, potentially required several hundred Fourier modes to be modeled accurately. However, simulations with such a high number of Fourier modes is not feasible as the computer resources (RAM) and computational time needed grow exponentially. Furthermore, for very small textures, RCWA converges with the GenPro4 flat model as is expected for sufficiently small textures. Nevertheless, integration of RCWA with GenPro4 was achieved. To demonstrate the ability to quickly and easily simulate real work cell designs, a case study of a perovskite/silicon tandem cell was conducted. In the case study, a combination of 16 interface mythologies was simulated and compared. With the optimal combination showing a potential improvement of 2% over the reference cell.

Brain aneurysms cause almost 500,000 deaths in the world every year. A better understanding of brain aneurysm genesis and rupture may open new opportunities to prevention and treatment. In this study, a part of the cerebral vascular system, the so called circle of Willis including an aneurysm, was analyzed with Computational Fluid Dynamics (CFD). The importance of boundary conditions in an aneurysm simulation was assessed by comparing the results to 7T MRI velocity data, obtained from the Academic Medical Center (AMC) in Amsterdam. Adequate similarities were found in velocity values, together with qualitative agreement in wall shear stress (WSS) values. We found that in a patient-specific case with an aneurysm, the velocity profile was able to develop to a parabolic profile because of its location; the aneurysm existed far downstream of the circle of Willis. This implies that it is possible to use a cropped arterial system to simulate the aneurysm and to use parabolic inlet velocity profiles for patients with this aneurysm phenotype. In previous studies, it proved hard to locate the precise location of rupture in an aneurysm. A risk assessment of the rupture location in an aneurysm can be used as a more accurate tool to assess the need for surgery. The aneurysm geometry of the CFD Rupture challenge from 2013 was simulated to predict the location of a rupture site. This rupture location was predicted by combining the following hemodynamic criteria: the time-averaged wall shear stress (WSSTA), oscillatory shear index (OSI) and vortex-saddle point structure during systole with accompanying low pressure values. A sensitivity study was performed on these criteria and a critical threshold for rupture risk was proposed. Based on these criteria it was possible to predict the exact rupture site for two analyzed aneurysm geometries. It is concluded that a CFD model could be used to assess the hemodynamics in intracranial aneurysms. Future research should focus on repeating this study on more patient specific aneurysm geometries to verify this hypothesis further.

This work investigates low-cost three-dimensional (3D) ultrasound reconstruction from a two-dimensional (2D) hand-held probe with motion tracking. The best available motion tracking is an optical tracking system, which is expensive and requires external tracking hardware. Here, a low-cost manoeuvrable motion tracker, an inertial measurement unit (IMU) sensor, has been tested by comparing it with an optical tracking system. The motion of the probe has been divided into a rotation and translation movement. Comparing the IMU sensor rotation tracking with the optical tracking, while rotating 40 degrees, resulted in an average Pearson’s correlation of 0.99 ± 0.0056. The average Pearson’s correlation between the translation tracking of the IMU sensor and the optical tracking system, in a translation of 15 centimetres, was 0.13 ± 0.78. The rotation and translation tracking is used to reconstruct the ultrasound volume of a phantom. In a rocking motion reconstructed volume the horizontal distance between phantom features had a mean error of 45%, a vertical distance was reconstructed with a mean error of 0.25%. In a translation motion reconstructed volume these errors were 29% and 1.4% for respectively horizontal feature distance and vertical feature distance. This study demonstrates that an IMU sensor can be used to track the motion of the probe. The rotation tracking of the IMU sensor is comparable with the rotation tracking of an optical tracking system. The translation tracking of the IMU sensor is on average not comparable with an optical tracking system, however some translations have been tracked with a high correlation. A reason to explain the low average correlation of the translation tracking of the IMU sensor is the method of gravity vector correction in the accelerometer data. Future research should focus on the clinical evaluation of the rotation tracking and the development of an accurate translation tracking method by studying the initial gravity vector or looking at different translation tracking methods.

Cardiovascular diseases are one of the leading causes of death worldwide, for example by causing strokes. Timely diagnosis of such diseases is pivotal for a patient’s chance of survival. Furthermore, in the present world in which medical expenses are going through the roof, we can save greatly on costs if certain diseases are detected in an earlier stage. To that end, our research is focused on improving medical measurement techniques, to give doctors a greater arsenal to combat these diseases. Ideally, a measurement technique is cheap, accurate, and all while causing minimal discomfort to the patient. Light-based techniques have proven previously to have great potential to fulfil that role. For example, that tiny device that you can put on your finger, and similarly the sensor in a sports watch, are able to measure your heart rate using light. For our research we have developed a computer model, such that we can use the power of modern computing. Our model is able to predict how light is reflected by red blood cells flowing through an artery. The computer is then able to rapidly simulate many scenarios, producing a lot of data about what the reflected light looks like for each scenario. From that data, we are able to say something about what a certain pattern in the reflected light says about the underlying system: the flowing red blood cells. As a first step, we have used our model to figure out how we can determine the heart rate from the reflected light. You could argue that that’s nothing special, as your sports watch can already do precisely that, but it’s an important step nonetheless, since our technique is different than what your sports watch is doing. Namely, the data our technique provides is more complex, but as a consequence also contains much more information and thereby yields a greater potential if we just become able to extract that information from the data. Therefore, our second step was to determine the exact velocity of the red blood cells from the reflected light, which is quite of a magical thing when you think about it: even though we cannot ‘see’ the red blood cells directly, we can still ‘see’ how fast they are moving. Although we succeeded in determining the velocity, in reality a doctor will likely need to do some tweaking to account for patient-specific factors, such as skin tone. Finally, we studied the disease atherosclerosis, in which accumulating cholesterol causes arteries to become more narrow, which ultimately could lead to a stroke. The narrowing of an artery, alters the flow behavior of the red blood cells, which we were able to pick up by studying changing patterns in the reflected light from our simulations. By extension, it should be possible to use reflected light to detect atherosclerosis, rapidly and cheaply flagging patients who are at risk. We have shown the potential of reflected light techniques for medical diagnosis purposes. Although further research and work is still required to put these techniques into practice for doctor’s to use, we have set the groundwork to enable these techniques in the not-too-distant future. @en

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.

inPhocal, a startup company specialized in laser marking, developed a novel optical module to make the depth of focus more than 50mm, and wants to replace ink marking by this laser marking system in the production line when marking information on products. Distortion will always happen when marking 2D patterns onto 3D objects with laser, so deforming the 2D patterns beforehand to make marked pattern keep its shape is necessary. This process is called shape correction. Nowadays, the way to do this shape correction is very complicated and time- consuming. This thesis is focused on providing a new method that can do shape correction easily and fast. In this research, Non-Uniform Rational B-Spline (NURBS) is used in reconstructing the 3D surfaces and the shape correction will be based on these NURBS surfaces. With this NURBS-based shape correction, the pattern can be mapped on to 3D object fast without distortion.

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.

Future industrial lithography machines will use interferometers for wafer-stage position metrology. Interferometers suffer from phase wrapping, which is why in this thesis an absolute phase detection system has been developed. The absolute phase detection system will use two lasers, with the second laser allowing for limited changes in the wavelength. An efficient implementation of the excess fractions method has been developed to perform the absolute phase capture. To improve the longevity of the system the second laser should ideally be allowed to turn of when not used for absolute phase capture, which requires a wavelength estimation algorithm. Such a wavelength estimation algorithm has been implemented, and it can also provide an initial estimate for the OPD of the interferometer to be used in the excess fraction method. Both the excess fractions method and the wavelength estimation method have been experimentally verified. The results were satisfactory, thus providing all the building block for an absolute phase capture system.

This work delves into designing and implementing an optimized self-centering lens mounting technique for the collimator and coupler lenses in the Universal Light Source (ULS) by ASML. The ULS aims to meet the growing demand for smaller logic nodes and higher throughput in optical metrology sensors. To achieve precise alignment and stability, the light source utilizes a supercontinuum spectral shaping method based on a highly non-linear hollow core anti-resonance photonic crystal fiber filled with a high-pressure noble gas. This research identifies the limitations of the existing lens mounting design in terms of manufacturing, stability, and adhesive usage. To address these challenges, a self-centering design is proposed, leveraging the geometrical relationship between thread angle, barrel and retaining ring diameters, and lens clearance. By optimizing these parameters, the centering error is substantially reduced, demonstrating a considerable improvement in centering precision compared to the current method. Additionally, thermal effects are mitigated through a symmetrical design and local flexibility, reducing the impact of temperature fluctuations during operation and transportation. An analytical assessment of five different collimator and coupler lens mount concepts are presented to identify an optimal design meeting specific operating temperature, stresses, eigenfrequency, and manufacturability criteria. Numerical analysis is employed to evaluate the performance of each design concept relative to the currently employed mounting designs. The resulting optimized self-centering coupler and collimator lens mount exhibits centering errors influenced by various tolerances. These tolerances have a deviation of ±0.2% for the lens radial surface, ±1° for the thread angle, and ±0.2 mm for the remaining parameters. The calculated centering errors for coupler lens and collimator lens 1 and 2 are 6.27 μm, 8.24 μm, and 6.98 μm, respectively. However, it is crucial to acknowledge that these results are purely theoretical and necessitate validation through experimental data to ascertain their accuracy. Overall, this optimized self-centering technique offers enhanced stability, relaxed manufacturing tolerances, and eliminates the need for adhesives when compared to the current flexure design. These significant findings contribute to the advancement of optomechanical engineering and provide valuable insights into the implementation of self-centering mounts, thereby enhancing precision while relaxing manufacturing requirements in optomechanical mounting.

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.

Flatness is an important surface tolerance requirement during the manufacturing of a part of an ASML machine. Flatness can be measured by either measuring the variation in height of the surface in one measurement (a plane-wise measurement) or by measuring the height on multiple xy-coordinates on this surface (point-wise measurement). Point-wise distance measurement sensors tend to have small physical dimensions, while having good specifications on resolution perpendicular to the measured surface. During a separate research, a gap is found in performing a point-wise flatness measurement while accounting for undesired stage deviations. The stage deviations are in the order of micrometers, while the sensor accuracy is in the order of nanometers. The performance of a point-wise flatness measurement is therefore in a negative sense dominated by the stage inaccuracies rather than sensor performance. During this research the gap is filled by designing, building and testing a feasibility demonstrator which uses reference sensors to account for stage inaccuracies. By performing a live correction with either 1 or 3 reference sensors, the stage inaccuracy (in z, Rx and Ry) can be compensated for. The measured stage wobble for this specific setup is 3.2 µm, which is reduced to 0.13 µm when using three reference sensors. The method of using reference sensors for flatness measurements is shown to work, mainly when using 3 reference sensors.

Single photon detectors are an important optical sensing tool in many industries. However, these highly efficient detectors suffer from variations in the size of an optical cavity when cooling down to 3K. An active positioning system is therefore required to correct the relative position of the fibre to the detector, so an optimal and reproducible cavity size can be achieved, thereby maximizing their efficiency. The literature study performed on cryogenic precision actuators showed that a stepper motor in combination with a motion reduction mechanism is the most feasible design. A stepper motor and a precision screw were two fundamental components of the preliminary design, so their lubrication was removed and were proven to work cryogenically. The rest of the design was based around these fundamental components. Room temperature tests were done to show the functionality of the design and it showed a positioning resolution between 10 nm and 30nm with just a 100nm loss of motion when unloading and loading the system. Cryogenic tests achieved similar results and it showed that the reflected power of a detector was reduced from 8.8% to 3.6%, indicating that the maximum achievable detector efficiency increased from 91.2% to 96.4%.