De missie van het lectoraat Fotonica is om een bijdrage te leveren aan een gezonde wereld en een duurzame economie door het toepasbaar maken van fotonicatechnologie in de praktijk. Ook draagt het lectoraat bij aan het opleiden van professionals op het gebied van fotonica, wat een voorwaarde is om de ambities van deze groeisector waar te kunnen maken. Het fotonica-onderzoek richt zich op de toepassingsgebieden Hightech Industrie, Agri & Food, Energie & Klimaat, Gezondheid en Mobiliteit. Digitale technologie speelt in de ontwikkeling van deze gebieden een grote rol, waarbij fotonica op grote schaal wordt ingezet voor het verkrijgen van digitale data. Sleutelwoorden voor het onderzoek zijn spectroscopie, metrologie en afbeelding. Het toepassen van optische sensoren, zoals spectrometers of glasvezel-gebaseerde sensoren, speelt hierbij een centrale rol. De lijfspreuk van de natuurkundige Heike Kamerlingh Onnes ‘door meten tot weten’, aangevuld met ‘door weten tot handelen’, is dan ook een leidraad voor het lectoraat.
DOCUMENT
Light scattering is a fundamental property that can be exploited to create essential devices such as particle analysers. The most common particle size analyser relies on measuring the angle-dependent diffracted light from a sample illuminated by a laser beam. Compared to other non-light-based counterparts, such a laser diffraction scheme offers precision, but it does so at the expense of size, complexity and cost. In this paper, we introduce the concept of a new particle size analyser in a collimated beam configuration using a consumer electronic camera and machine learning. The key novelty is a small form factor angular spatial filter that allows for the collection of light scattered by the particles up to predefined discrete angles. The filter is combined with a light-emitting diode and a complementary metal-oxide-semiconductor image sensor array to acquire angularly resolved scattering images. From these images, a machine learning model predicts the volume median diameter of the particles. To validate the proposed device, glass beads with diameters ranging from 13 to 125 µm were measured in suspension at several concentrations. We were able to correct for multiple scattering effects and predict the particle size with mean absolute percentage errors of 5.09% and 2.5% for the cases without and with concentration as an input parameter, respectively. When only spherical particles were analysed, the former error was significantly reduced (0.72%). Given that it is compact (on the order of ten cm) and built with low-cost consumer electronics, the newly designed particle size analyser has significant potential for use outside a standard laboratory, for example, in online and in-line industrial process monitoring.
MULTIFILE
Poster presentatiion, project Printing Makes Sense at Saxion Research Conference 2018, Deventer. Photonics is declared one of the key enabling technologies by the European Commission. Photonics finds its application in many fields ranging from health & well-being to smart industries. Automation in photonics manufacturing and packaging is key to reduce assembly costs. At the NanoPhysics Interface group, we investigate how to quickly couple light from one fiber to another fiber (or photonic devices). After developing a theoretical model and performing measurements, we find that the alignment is most critical in the lateral translations (x and y-direction) and that pre-alignment of the photonic components can be realized by a smart design of the chip holder
MULTIFILE
Micro Ring Resonators (MRRs) have become the workhorse in photonics, both for data/telecomas well as bio-chemical sensing applications. In this contribution the use of MRRs as sensors for food-safety applications will be discussed.
MULTIFILE
From the article: "The term Internet of Things (IoT) is used for situations where one or more devices are connected to a network or possibly the Internet. Most studies focus on the possibilities that arise when a device is capable to share its data with other devices or humans. In this study, the focus is on the device itself and what kind of possibilities an Internet connection gives to the device and its owner or user. Also the data the device needs to participate in a smart way in the IoT are part of this study. Agent technology is the enabling technology for the ideas introduced here. A proof of concept is given, where some concepts proposed in the paper are put into practice."
MULTIFILE
We report on the calibration and testing of a fiber Bragg grating (FBG)-based 2D-shape sensing strip for real-time monitoring of the position and orientation of the human spine during gait. The strip is evaluated for its use as an input for control of an exoskeleton for patients with spinal cord injury. By measuring the torsion and bending of the back, walking movements can be reconstructed. The 3D-printed strip has nine embedded fiber Bragg gratings that are located at specific places with respect to the vertebral column. Three FBGs are placed opposite to the thoracic vertebrae T6–T9, these FBGs are sensitive for measuring the bending of the spine during the gait cycle. Torsion is measured at two locations: at thoracic vertebra, T3 and at lumbar vertebra, L3. At these locations, the width of the strip is reduced to have a larger sensitivity for torsion. The strain at each FBG is measured using an interrogator. This leads to the radius of curvature and torsion as a function of time. The Frenet-Serret formulae are used to calculate the shape of the strip during the gait cycle. We have calibrated this FBG strip for curvature by bending it at known radius of different curvatures. We found a linear dependence between the strain and curvature. For torsion calibration we have rotated the strip with a stepper motor at different angles and monitored the strain. We, again, found a linear dependence with a small hysteresis. We mounted the strip on a healthy test subject and monitored their gait cycle. The FBG strip shows similar results when compared to a motion capture system based on multiple cameras. Although the fixation of the strip to a garment or on the back directly strongly influences the measured response, it does show a periodic and reproducible signal during the gait cycle.
DOCUMENT
Spectral imaging has many applications, from methane detection using satellites to disease detection on crops. However, spectral cameras remain a costly solution ranging from 10 thousand to 100 thousand euros for the hardware alone. Here, we present a low-cost multispectral camera (LC-MSC) with 64 LEDs in eight different colors and a monochrome camera with a hardware cost of 340 euros. Our prototype reproduces spectra accurately when compared to a reference spectrometer to within the spectral width of the LEDs used and the ±1σ variation over the surface of ceramic reference tiles. The mean absolute difference in reflectance is an overestimate of 0.03 for the LC-MSC as compared to a spectrometer, due to the spectral shape of the tiles. In environmental light levels of 0.5 W m−2 (bright artificial indoor lighting) our approach shows an increase in noise, but still faithfully reproduces discrete reflectance spectra over 400 nm–1000 nm. Our approach is limited in its application by LED bandwidth and availability of specific LED wavelengths. However, unlike with conventional spectral cameras, the pixel pitch of the camera itself is not limited, providing higher image resolution than typical high-end multi- and hyperspectral cameras. For sample conditions where LED illumination bands provide suitable spectral information, our LC-MSC is an interesting low-cost alternative approach to spectral imaging.
MULTIFILE
From the article: "A facile approach for the fabrication of large-scale interdigitated nanogap electrodes (nanogap IDEs) with a controllable gap was demonstrated with conventional micro-fabrication technology to develop chemocapacitors for gas sensing applications. In this work, interdigitated nanogap electrodes (nanogap IDEs) with gaps from 50–250 nm have been designed and processed at full wafer-scale. These nanogap IDEs were then coated with poly(4-vinyl phenol) as a sensitive layer to form gas sensors for acetone detection at low concentrations. These acetone sensors showed excellent sensing performance with a dynamic range from 1000 ppm to 10 ppm of acetone at room temperature and the observed results are compared with conventional interdigitated microelectrodes according to our previous work. Sensitivity and reproducibility of devices are discussed in detail. Our approach of fabrication of nanogap IDEs together with a simple coating method to apply the sensing layer opens up possibilities to create various nanogap devices in a cost-effective manner for gas sensing applications"
MULTIFILE
Het tekort aan handjes in de accountancy neemt toe. Tegelijk groeit de maatschappelijk druk om bedrijven zo goed mogelijk te controleren, om te zorgen dat ze financieel, fiscaal en qua duurzaamheid in de pas blijven lopen met de (toenemende) regelgeving. Gelukkig komt er steeds meer technologie voorhanden die de accountant kan helpen bij het controleren van de boeken, schetst Eric Mantelaers, hoofd Bureau Vaktechniek, RSM Accountants. Medio juni is hij aan de Open Universiteit gepromoveerd op zijn proefschrift ‘An evaluation of technologies to improve auditing’.
LINK
The stability of upstream deposited tailings dams is dependent on maintaining a drawn down phreatic surface and unsaturated profile in its outer edge. However, it has been speculated that intense rainfall events could induce unexpected translation of pore air and water pressures into the tailings profile and thus compromise the effective stress in the unsaturated zone or result in a sudden rise in the phreatic surface. This phenomenon, known as the Lisse effect, has been observed and studied in hydrological sciences to explain the rapid delivery of antecedent hillslope groundwater during storm events. However, the phenomenon has not been comprehensively applied to evaluating tailings dam slope stability. In this paper, the outcomes of controlled observations of the phenomenon in column and analytical experiments, are assembled and evaluated in terms of the surface water application volumes and rate, the properties of the porous media and the resultant nature of pore pressure and phreatic surface responses. In addition, application of applied theories to evaluate the rapid transmission of pore pressures through a profile in response to an advancing wetting front, leads to the development of a methodology that could be applied to tailings materials of a range of hydraulic conductivities and water retention characteristics. The theory is applied to a series of profiles of different tailings porous media, using varied water application rates. Resultant perturbations in phreatic surface elevation and changes to pore pressures in the unsaturated zone are used to evaluate changes in effective stress distribution in the unsaturated outer wedge and subsequent stability criteria. A possible evaluation algorithm for assessing stability criteria is suggested.
MULTIFILE
