This report discusses one part of a project consisting of three parts. The goal of the project is to design a battery less sensor powered by RF energy fields present in an office environment. The sensor is able to measure the temperature and is able to communicate wirelessly using a low power communication protocol.In this report the energy conversion and storage of the system will be discussed. A high-frequency signal coming from an antenna must be converted to an output signal which is functional for the communication module. Therefore a steady 3.3 V DC output needed to be created with a rectifier circuit. In order to achieve maximum power transfer to the load, a matching circuit with the RF energy harvesting antenna needed to be designed. The main challenges were to achieve a high enough input voltage to reach the threshold voltage of the diodes of the rectifier and to rectify the AC input as efficient as possible. To tackle these challenges a design with a Greinacher rectifier with low-threshold Schottky diodes and a DC/DC booster is presented.

The objective of the bachelor graduation project detailed in this thesis is to develop a wireless sensor patch that monitors the health of newborns. The sensor patch replaces the monitoring tasks of nurses during maternity care. The patch measures temperature, heart rate, oxygen saturation and bilirubin. Many babies are born with high bilirubin, causing a condition called newborn jaundice. All measurements will be done once every two hours and the data will be sent to the hospital. This thesis focuses on everything related to energy and power within the wireless sensor patch. Energy storage, power and energy management and visualising data with the aid of a MATLAB model are topics that will be designed and implemented in this thesis.

Predicting when a neonate will fall victim to an infection or a disease allows prevention through early medicine administering. Such physiological conditions can be made visible using infrared thermography (IRT). This is a technique for measuring heat emitted in the infrared spectrum and transforming them into visible signals that can be recorded photographically. This thesis will contribute to the prediction of infection in (pre)term neonates by quantifying the interaction between IRT and a neonatal incubator without (and with) a neonate in it.  A system was designed that consisted of three modules: a measurement (incubator and IRT camera), back-end (embedded system and server), and front-end module. The scope of this thesis is limited to the measurement module and the embedded system of the back-end module. Minimum camera requirements were set up which required the camera to: be inexpensive (i.e. ≤ €1000,-), be mobile, be open-source (for Linux), have a minimum frames-per-second of 5, have a resolution of at least 160x160 pixels with a field of view (FOV) of 27°, sensitivity of < 0.1°C, and safe to the patient. Such a camera was found in the FLIR One Pro. For this thesis a different FLIR camera was used due to lack of budget, namely the FLIR A305sc, which was already available at the TU Delft. The A305sc is not open-source, which required a work-around. The Aravis Open Source Project allowed for communication with the camera. Internal camera parameters had to be determined to calculate temperature based on analogue-to-digital values. ExifTool was used on a file stored by the camera to extract these parameters. This calculated temperature was compared to the temperature as determined by FLIR’s software and led to a difference in the range of 1·106°C. An open-source application was written that can connect with this IRT camera that has a GenICam interface using Aravis. Additionally, this application implemented the temperature calculation based on the internal camera parameters. The hood of the incubator is opaque to infrared, which required the design of a measurement setup to circumvent this. Three different setups were discussed, with the final choice falling on placing the camera in front of an opened incubator porthole on a tripod, and sealing this porthole with high or low density ethyl polyethylene (HDPE/LDPE). Regular H/LDPE used for construction site was found to have a attenuated transmissivity as found in literature. To quantify the interaction between IRT and a neonatal incubator, the IRT measurements were to be compared against the current golden standard sensor, namely thermistors. These sensor values were to be read out from the incubator as this would also be used in the final product. Code was written which allows for automatic detection between the GE GiraffeTM Omnibed and the Dräger Caleo® incubator, automatic connecting, and manipulation of all sensors values to a standard string which allows for easy uploading to the InfluxDB database on the server. To be allowed to perform measurements on human subjects, approval had to be acquired by the human research ethics committee (HREC) of the TU Delft and the respective hospital. A “non-wet medisch wetenschappelijk onderzoek met mensen” (nWMO) request was submitted and approved, which resulted in 25 recorded sick and healthy neonates in incubators divided over two hospitals (the JKZ in The Hague, and the RDGG in Delft), with over 25 hours of recording material. Simultaneously, measurements were performed on an empty incubator to gain an understanding in the behaviour of an incubator when actors from outside interacted with the internal environment. Measurements that were performed included determining the reflected apparent temperature (RAT) for every possible opened porthole and for both incubator types. The RAT for the Caleo was found to be higher for every measurement for the GE. The accuracy of the IRT and hospital skin temperature sensors was compared against a calibrated Pt-100 sensor, which show that the Pt-100 sensor measures an equal value as the hospital skin temperature sensor, whereas The IRT camera measured .6°C higher. The effect of changing the distance on IRT values was measured, which shows that for a distance of 0.2m to 1.2m the accuracy of the IRT camera is within the specified accuracy. Finally, the effect of opening additional portholes on IRT was measured, the effect of the airboost setting on IRT, and the measurement of opening additional portholes was repeated with a different IRT camera. Overall the IRT camera measures a higher temperature than the hospital skin temperature sensors, but follows the skin temperature sensors’ pattern.    

Myocardial ischaemia induced by cardioplegia is the most prominent risk during open-heart surgery. To achieve adequate protection of the cardiomyocytes during surgery, the cardioplegia must arrive at all cardiomyocytes. Local obstruction can lead to regional ischaemia. For surgeons and perfusionist, the arrested heart is a black box. They know how much cardioplegia they are administering to the heart. However, they do not know if cardioplegia is reaching all cells. This work describes which parameters can be measured during cardioplegia induced cardiac arrest and compares the methods used in the literature to detect these parameters. Following this, it is the goal to create a proof-­of-­concept sensor for the detection of myocardial ischaemia. A literature review indicated that a fluorescent optochemical pH sensor has the most potential. To be able to develop a proof-­of-­concept, optical, chemical, and medical knowledge needs to be combined. This is necessary to map what is required and what is possible for optochemical in vivo sensing. First, a framework is designed and used to select the best technique and material suited for this project. In this framework, the medical requirements and the resources available are combined. As a result, this thesis work will use a dual wavelength pH­-sensitive fluorescent dye encapsulated in a biocompatible hydrogel. In preparation for the proof-­of-­conceptsensor, multiple samples are fabricated and extensively tested to achieve the optimal sensing layer. Using the optimised concentrations, a proof-­of-­conceptsensor is created using a miniature reflection probe and an USB spectrometer. This proof-­of-­conceptsensor shows that it can measure the changes in pH and can be corrected for multiple interferences. It also shows the potential to be further miniaturised and to be used during cardiac surgery. Before this can happen, chemical optimisation of the sensing layer is needed, and the consistency of the sensing layer needs to be improved. However, besides this, the work succeeded in selecting an optochemical sensing technique and material which shows the potential to be used in cardiac surgery

[Background] This project provides a proof of principle to use microneedles in combination with optical spectroscopy for bilirubin detection. For newborns, high bilirubin levels in the blood can lead to serious health consequences, such as jaundice, which can lead to brain damage. Therefore, it should be detected as early as possible. However, bilirubin monitoring of newborns in remote African areas is insufficient. In these areas the current invasive methods are time-consuming, and minimally invasive methods, such as bilirubinometers, are quite expensive, and may be inaccurate in babies with stronger skin pigmentation. In short, the conditions are not optimal to detect jaundice, and therefore an affordable method is needed to accurately and quickly measure the concentration of bilirubin. [Aim] The aim of this project was to develop microneedles for optical spectroscopy, and to test them in simulated skin to determine the usability for reflection measurements. [Fabrication] Microneedles are created by using microfabrication techniques with a focus on backside exposure. Multiple prototypes have been developed and evaluated based on dimensional properties. The prototype closest to the requirements was chosen to take measurements. These were the microneedles with an average length of 410 μm, an average base diameter of 106 μm and an average tip diameter of 43 μm. [Measurements] To test the microneedles for their performance, an indentation test, and transmission and reflection measurements has been performed. The indentation test showed that the average fracture point of one microneedle is at a force of 72.5 mN and an average displacement of 63 µm. The fracture point per area microneedle is on average 16.5 N/mm^2. Furthermore, transmission measurements have shown that the reduction in transmission is 70 % from the base and 75 % from the tip. Therefore, the maximum amount of light that can be used for reflection measurements is 7.5 %. Moreover, reflection measurements have shown that the differences in color concentrations in the simulated skin results in differences in absorption and therefore reflection values. Also, the measurements in simulated bilirubin (skin simulation with yellow colorant) showed a dip in the blue spectrum, e.g. at 460 nm, the absorption peak of bilirubin. [Conclusion] In this project microneedles have been developed that are minimally invasive, biocompatible, optically transparent, and easy-to-process. The first measurements have shown that it seems possible to use the microneedles in combination with optical spectroscopy to detect differences in “bilirubin” concentrations. Moreover, the microneedles can be used to puncture the skin without fracturing. However, the actual usability in the clinical setting still needs to be investigated. Other important recommendations for future research are research into measurements with real bilirubin; the optimal alignment between the microneedles and the optical spectrometer; optimization in the manufacturing process to cover the spaces between the microneedles; and possible other development methods for microneedles (e.g. 3D printing) and other designs (e.g. mirrors for efficient light use).

This research investigates the feasibility of a sensor patch for newborns. A sensor patch would be a device that is applied to the skin of the newborn. It can monitor the patient's temperature, heart rate, respiration rate, oxygen saturation and asses its general appearance of the skin so that it can check the newborn for jaundice. It should then communicate wirelessly to a base station which should have a compatible communication protocol. What happens after receiving of sensor data at the base station is beyond the scope of this project. One of the major challenges in the design process is energy efficiency, since the device should be small enough to fit on a baby and the battery should thus also be small. Additionally, the sensor patch should be able to operate for 3 days continuously. The overall design comprises sensors, a battery with battery control system, a microcontroller and a communication module. The overall design is split up over three reports. This report focuses on implementing the microcontroller and communication protocol. It is found that using a design with separate microcontroller and communication device is more efficient than using a so-called System on Chip where all of this is mounted on a single device. Then a comparison between different microcontrollers, communication protocols and communications devices is made. It is found that a design with an MSP430FR5994, Bluetooth Low Energy protocol and RSL10 communication chip fits the requirements best. The research concludes that with the chosen hardware it is possible to meet the set requirements for the subsystem. Further research still needs to be done towards optimising software for the chosen devices.

In this thesis, the implementation of a passive, chipless, frequency coded Radio-Frequency Identification (RFID) tag for bedload transport studies is proposed. The proposed tag will be deployed in the semi-arid Río Colorado river, Bolivia with the aim to develop quantitative sediment transport models that relate transport to grain size. The designed tag is an open-loop resonator with a fragment-loading structure, that has an op- timised configuration based on a Multiobjective Evolutionary Algorithm based on Decomposition combined with Enhanced Genetic Operators (MOEA/D-GO). The designed RFID tag can ideally reach a size of 4 by 4 millimetres with a maximum calculated reading range of 1.3 meters, and operates in the ultra wide band from 3 to 7 gigahertz. Numerous simulations on the tags were run to verify their properties. The tags proved to have a good directivity, quality factor and radio cross section on its resonant frequency. The tags could reach resonance frequencies as low as 2.9 gigahertz and quality factors as high as 130. The proof of concept on a Printed Circuit Board with an FR-4 substrate results in a tag of 6.4 by 3.4 millimetres. Unfortunately, these properties could not yet be verified by measuremen

In this research a sensor patch for newborns is proposed. This sensor patch is a device which would be attached to the skin of a newborn in order to monitor vital health signs such as: temperature, heart rate, respiration rate and oxygen saturation. Furthermore, a bilirubin sensor will be included to check the newborn for jaundice. Thereafter, the measured data should be communicated wirelessly to a base station. What happens with the data after the base station is beyond the scope of this research. One of the main challenges is energy efficiency since the patch should be small enough to fit on a newborn whichmeans the battery should be small as well. Additionally the sensor patch should be able to operate for 3 days continuously. The overall design is divided into three subsystems: the battery control system, the microcontroller and communication and the sensors. This report focuses on the sensor part of the total system. After analysis of different kind of sensors, the SI7051 is chosen for the temperature sensor since it is themost accurate and energy efficient. In order to measure the respiration rate an acceleration sensor was chosen to be the most suitable within the system requirements. For the acceleration sensor the IIS2DLPC was selected. In order to measure the heart rate and oxygen saturation a PPG sensor is designed. Finally, the bilirubin sensor is designed which uses PPG as well. However, the designed sensors still need calibration by empirical experiments in order to obtain accurate results

In this thesis, the implementation of a passive, chipless, frequency coded RFID detection system for bedload transport studies is proposed. The proposed tag will be deployed in the semi-arid Río Colorado, Bolivia with the aim to develop quantitative sediment transport models that relate transport to grain size. Different algorithms are explored and implemented in Matlab and measurement results are discussed.

This report discusses one part of a project consisting of three parts. The goal of the project is to design a battery less sensor powered by RF energy fields present in an office environment. The sensor is able to measure temperature and is able to communicate wirelessly using a low power communication protocol. In this project the use case of a building is explored. In this thesis the possibilities of low power sensing, processing and communicating are investigated. Different options for sensing, processing and communication chips are discussed. Measurements in terms of communication range and power consumption are performed on the system. A TMP-102 temperature sensor, an ATtiny84A microcontroller and an SX1272 LoRa module are chosen. Roughly 4 mJ is needed to perform a measurement and transmit it. Further research is needed to reduce the energy consumption even further.

This thesis discusses the theory, circuit design, software design and measurements of an atto-Farad resolution closed-loop impedance measurement bridge circuit for capacitive sensors implemented using commercial off the shelf components. A lock-in amplifier (LIA) method is used here. The capacitive sensor embedded in an impedance bridge is driven at 10MHz or higher by two inverting excitation sources (AD9959) that can adjust frequency, phase and amplitude with a certain resolution (32 bits, 14 bits and 10bits respectively). These parameters can be set through a graphical user interface (GUI). When the output signal is nulled by changing the amplitude of the excitation signal, the unknown capacitor value can be calculated. A simple test impedance bridge has been fabricated to measure a fixed impedance value of the capacitor sensor using the LIA measurement approach. The obtained results (capacitance and resistance values) are in good agreement with what we obtained using an alternative approach (AH2700A, is an ultra-precision capacitance bridge with 0.16ppm resolution at 1000Hz). The circuit has a 24.1ppm resolution at 10Hz bandwidth when the input frequency is 10MHz.

This report discusses one part of a project consisting of three parts. The goal of the project is to design a battery less sensor powered by RF energy fields present in an office environment. The sensor is able to measure the temperature and is able to communicate wirelessly using a low power communication protocol. In this project the use case of a building is explored. This thesis treats the RF energy harvesting part, which scavenges the RF power out of the ether and delivers it to the rectifier to convert and store the energy. First the spectrum has been analyzed to determine the most suitable frequency band. An antenna has been designed to harvest as much power at the chosen frequency. To make the power transfer from the antenna to the rectifier as efficient as possible, a matching circuit for matching the impedances is implemented. In this report, a Planar Inverted-F Antenna is designed to meet all the given requirements.

Heart rate is a key factor in cardiovascular system monitoring and sports science. Some recent commercial applications use sensors in the ear but are faced with motion artifacts which corrupts the signal. In this report, a comprehensive review of heart rate detection methodologies was completed in order to find possible solutions with better performance. Infrared thermography is a non-contact technique and was selected because it may minimize motion effects with better user comfort and lower power consumption. Thermopiles were chosen as the sensors used in the system based on their responsivity, relevant wavelength detection and size. The anatomical distribution of the arteries in the external ear was studied in order to select the best position of the sensor. The cavum conchae and anti-tragus were studied considering the irrigation of the posterior auricular and superficial temporal arteries. The signal analysis was performed using a continuous wavelet transform which extract frequency features of the bioheat transfer waveforms. A digital sensor was evaluated first in the neck, nose, wrist and ear but did not render relevant results mainly due to quantization errors. Subsequently, analog thermopiles were studied with ultra-low noise amplifiers. First, the Noise Equivalent Temperature Difference from a ST150 thermopile was calculated using a Peltier cooler and a Pt100 reference sensor. This sensor was then used to measure the infrared signals of the wrist, neck and ear in order to find pertinent heart rate signal. Next, a smaller sensor was used to try compare the locations of the anti-tragus and the cavum conchae in the ear and under the effect of a fan. The fan did not had any effect on the measurement and the smaller sensor had significantly less signal than the previous sensor. The localization of the arteries was not possible as a result of the reduction on the detection area of the skin. Finally, the effect of the detection area of the skin was tested under 2 conditions using the ST150 thermopile. The results show that a separation of the sensor from the skin increased the detection area and the quality of the heart rate signal measured. The proposed system successfully uses infrared differential thermometry to detect the heart rate in the auricle.