This thesis presents the design, manufacturing, and characterisation of a multimode metal oxide-based gas sensor. The aim of the multimode sensor is to enhance selectivity by integrating a chemiresistive sensor with a quartz crystal microbalance (QCM) into a single microscale device. The motivation for this work is the limited selectivity of low-cost gas sensors compared to laboratory systems, while the proposed design maintains the ambition of low-cost fabrication, small size, and industrial applicability. The proposed sensor combines interdigitated chemiresistive electrodes, a quartz resonator, platinum heaters, temperature-sensing functionality, and a metal-oxide-sensitive layer into a single device. The design is supported by analytical calculations and thermal simulations, after which the sensor is manufactured using standard MEMS-compatible processes, including lithography, lift-off metallisation, TEOS deposition, metal oxide printing, and packaging.

The fabricated sensor is characterised using a platinum-doped SnO2 sensing layer and a sequential electrical read-out of metal-oxide resistance and resonance frequency. The chemiresistive mode shows the strongest performance, including VOC-1 detection and an estimated limit of detection. The QCM sensor shows a resonance frequency of approximately 7.67 MHz at 50 °C and a Q-factor of about 550, but its performance is limited by low resonance quality and a relatively high detection limit. Nevertheless, combining both sensing principles yields gas-dependent relations between chemiresistive sensitivity and frequency response for VOC-1, VOC-2, and VOC-3. This demonstrates that the monolithic multimode concept provides additional discriminatory information compared with either sensing principle individually. It is concluded that monolithic integration of a chemiresistive and QCM sensor can enhance selectivity, but further optimisation of the resonator design, measurement electronics, and thermal control is required before the concept can be used as a robust, selective detector at low concentration levels. ... Read more

This report covers the design of a high voltage power supply that is designed for seed disinfection applications using plasma activated water (PAW). The goal is to have a safe and reliable pulse power supply that can be used to power a Dielectric Barrier Discharge (DBD) load. Multiple setups were designed and analyzed. Different transformers were designed and compared with differing core dimensions, inner radius, number of windings and type of winding. Furthermore, a bipolar driver was built and tested. The results demonstrate that the current design is a solid foundation for small-scale plasma-activated water generation and that it can be scaled with a segmented setup consisting of multiple smaller loads. Future iterations should focus on improving thermal dissipation, switching efficiency, and transformer insulation. ... Read more

This thesis presents the design and characterization of a low-temperature plasma reactor for seed treatment applications, with a focus on the generation of ozone. The research will look at two different setups using dielectric barrier discharge (DBD) to generate plasma. The first design explores a coaxial tube setup, and the second design entails a multi-hollow plate setup. This research was done in collaboration with TU Delft and the Dutch seed distribution company Bejo Zaden BV, and its main objective was to develop a sustainable and efficient alternative to conventional seed disinfection. The initial tube design used an acrylic tube as the dielectric and two stainless steel electrodes, but this design had some issues so a revised design with smaller dimensions was made to address these issues. The multi-hollow plate design used two steel electrodes with holes (with diameters ranging from $1-2.5mm$) and a dielectric made of polylactic acid. The experimental results showed that both setups work. In order to assess the final design, a program of requirements was made, which included requirements such as sustainability, safety, and scalability. Key findings suggest that the electrode and dielectric materials were not optimal, but were sufficient enough to prove the concepts. This study aims to advance the sustainable agricultural practices by providing an efficient plasma-based seed disinfection method. Future recommendations include optimizing electrode and dielectric materials and scaling the system for industrial use.
... Read more

As integrated circuits (ICs) become increasingly miniaturized, traditional solder-based interconnects face challenges related to their thermal and mechanical performance, limiting their reliability in high-density applications. This thesis addresses the growing demands of the microelectronics industry, particularly in advanced semiconductor packaging technologies, by focusing on the development of innovative interconnect methods using metallic nanoparticles, specifically copper (Cu). The research aims to overcome these limitations by utilizing copper nanoparticle (CuNP) paste to achieve direct copper-to-copper (Cu-to-Cu) bonding through nanoparticle sintering. This technique is essential for enabling next-generation 2.5D and 3D IC architectures, which require dense interconnects for improved performance... ... Read more

Disinfection of seeds is a method used by the seed industry to remove pathogens. However, conventional methods have their shortcomings in terms of energy efficiency and yield. This thesis focuses on the design of a fluidized bed setup with sensors for the purpose of DBD plasma disinfection.
Two configurations were investigated, namely a spouted bed and a bubbling fluidized bed, where the bubbling fluidized bed produced the best results. Additionally, the fluidized bed was equipped with motor speed control, and with sensors for the measurement of ozone concentration, temperature, humidity, air speed, and ion density. These sensors were integrated in an easy readout system using displays, making the system ready for testing of disinfection performance.
... Read more

In a world where global warming is a growing issue, new solutions need to be found to reduce the carbon footprint. The same is true for the seed breeding industry, which uses energy inefficient ways of disinfecting seeds using hot water baths. A more eco-friendly solution would be the use of cold plasma treatment. This thesis proposes two designs for high voltage generators to achieve this goal. These include the supercascode switch for high voltage pulsed DC operation and the high voltage transformer driven by a ZVS driver to create high voltage AC. Simulations were performed from which it was verified that the supercascode circuit could switch an input DC voltage of 10 kV at 20 kHz. The ZVS driver-transformer combination was shown to be able to generate up to 10 kV peak with a frequency up to 22 kHz depending on the load. Experiments were conducted with the ZVS driver and transformer which was able to match the simulations. However, the transformer turned out to have a coupling coefficient of 87%, which was not enough to be able to generate plasma, as a coupling of around 95% would be required. ... Read more

This thesis describes the design and implementation of a LED Driving and Sensing Unit, one of the parts of a UV-C LED sterilization machine for the disinfection of plant seeds. The purpose of this part is to drive LEDs which can destroy different structures of pathogens. While doing this, certain parameters like temperature and ozone generation are being measured.
The report covers many design choices such as the choice to put the LEDs in arrays that are a combination of series and parallel circuits, or how SPI addressable variable resistors were used, in order to have full control over the LEDs and the sensing part. Furthermore, through a MATLAB script, it was discovered how the arrays of LEDs must be placed in specific manner to obtain a uniform radiation pattern. From this, it follows that using two arrays with radii of respectively 17 and 41 mm would work best. Furthermore, a literature research was done on UV-C and on what wavelength is theoretically the best for destroying pathogens on seeds. The focus was set on wavelengths of 255 nm and a combination of 275 nm and 285 nm. Also a 395 nm (UV-A) LED was used to investigate whether pathogens can be awakened from a hibernation state with the help of this type of light.
A boost converter capable of controlling the intensity of the LEDs by changing its gain with the aforementioned variable resistors was designed. Finally, the entire unit was tested successfully. The result of the research is a fully working LED driver module that can sense all parameters that need to be measured, completed with the design of a 3D CAD casing, which has all been manufactured and fabricated. This thesis does not include test results of the disinfection of plant seeds. This information will be included in the supplementary seed testing results report. ... Read more

This thesis presents the design and development of a UV-C LED-based seed treatment machine aimed at enhancing seed quality by the extermination of pathogens. The research covers design choices, including a round irradiation pattern, consisting of two rings with three and nine LEDs for the inner and outer ring respectively, the use of a quartz plate as a holding plate for seeds for its high UV-C light permeability capabilities, the use of a vibration motor underneath the main operational stack for seed movement, and the use of Ethernet ports for power distribution and communication. The thesis discusses a comparative study between square and circular plate configurations, evaluating their performance using simulation results. Safety considerations were prioritized in the design, and appropriate precautions were implemented throughout the design process. The thesis also highlights the iterative design process for the mechanical system, discussing challenges encountered and improvements made to achieve a functional and robust prototype. Results demonstrate successful integration of components and achievement of objectives. The thesis concludes with discussions on the strengths, limitations, and future enhancements of the UV-C LED-based seed treatment machine. The research presented in this thesis provides valuable insights for further advancements in seed treatment technology, contributing to sustainable agricultural practices. Due to time constraints, conclusive results of testing on seed with this machine could not be obtained yet. ... Read more

In this thesis for the Bachelor’s Degree in Electrical Engineering, a Control Unit (PCB and software) is designed for inside the UVC Seed Disinfection Machine of Team UVO. The machine consists of four modules: the Control Unit, the LED Driver, the motor controller and the power supply. The Control Unit allows a user to input the intensity per wavelength (for possible wavelengths: 255 nm, 275 nm, 285 nm and 395 nm), the exposure time and the motor speed.

The design of the machine, including all the modules, is aimed at achieving the optimal wavelength for inactivation and maximum and uniform irradiance, with the ability of changing radiation settings according to the desire of the user.

The Control Unit manages communication with the other modules, data storage, the User Interface, safety checks and system enabling. The thesis covers the design choices regarding the entire design, with an in-depth analysis of the hardware implemented safety checks, the graphical user interface and the design of the communication protocol.

Due to difficulties regarding uploading the code onto the PCB, not every developed functionality could be tested or implemented. However, the functionalities that were tested, did perform as expected. In addition to this, after the thesis has been submitted, more time will be spent on debugging the PCB, implementing and testing its features.

The objective for the graduation project of Team UVO is to provide a proof-of-concept of disinfecting cabbage seeds (Brassica oleracea capitata) from Alternaria using UVC LEDs. This thesis describes design process of the Control Unit module. The results of the decontamination process are provided in
Appendix F. ... Read more

Power electronics are an important technology used to convert electricity from a source like a battery or high voltage DC bus to more usable forms of electricity. This has to be done efficiently, reliably and without failures which is critical in applications like electric cars or datacenters. Power MOSFETs with upcoming SiC and GaN devices are an important building block used in these converters. Hence these power MOSFET devices have to be improved continuously to get a lower on resistance (R_DSon), a better thermal dissipation and lower parasitic losses. In this thesis we will take a look at the embedding of power MOSFETs inside a PCB to obtain these improvements. This new technology needs to be evaluated in terms of reliability, failure-modes and thermal/electrical performance. By designing,
manufacturing and testing a PCB with embedded devices. During manufacturing silver sintering has been used for attaching the die to a copper coin. In the end the manufacturing has been done successfully.
Testing showed an 18% lower R_DSon and a twice as low junction to ambient thermal impedance indicating a better performance compared to regular packaging. ... Read more

THERMAL management is a very crucial step to ensure the reliability of Integrated Circuits (IC)s. The increase in power density has resulted in the formation of multiple, high-intensity, and non-uniform hotspots. This has not only affected the lifetime but also the performance of several devices. Optimization of the package design and layout are the methods investigated to solve this problem. In flip-chip packaging, each IC product varies with respect to power densities, die area, pin-count, laminate and PCB layers, etc. It is therefore important in understanding how the arrangement and geometry of each layer (in particular the interconnect layer) impacts the overall thermal management. ... Read more

The current COVID-19 pandemic shows the necessity of personal protective equipment and face masks. In the project, a filter module with an in-situ ultraviolet-sterilization technique is designed that can serve as a new kind of smart personal protective equipment (SPPE). This technique is not used in wearable devices as of yet. The project thus aims to take the next step into the future of facemasks. The complete SPPE design is split into three submodules. In this thesis, the Sensing and Control submodule is designed. The Sensing and Control submodule is divided into three parts as well. In the first part of the design, a negative feedback control loop is developed. A photodiode transimpedance amplifier circuit provides the feedback, and the controller is programmed on a microcontroller. The control parameters are derived from a model in Simulink. In the second part of the design, the temperature and relative humidity are measured to transform the control loop’s reference value into a reference function. In the third part of the design, an estimation of the filter state of health is made by measuring the pressure drop over the filter material. Additionally, the airflow in the SPPE is calculated using equations from fluid mechanics to set the maximum allowable pressure drop. At the end of the thesis, the Sensing and Control submodule allows the SPPE to measure environmental conditions, control the ultraviolet intensity accordingly, and indicate if the filter requires replacement. The design is finalized with printed circuit board designs and an algorithm. With the design of the Sensing and Control submodule, the next step is taken towards the future of face masks. ... Read more

The Smart Personal Protective Equipment (SPPE) is proposed as a result of the COVID-19 pandemic, which has led to shortages of standard face masks. This thesis describes one of the three subsystems of the SPPE, namely the Ultraviolet Germicidal Irradiation (UVGI). The UVGI subsystem provides the SPPE with an in situ disinfection system, in order to prolong the period in which the filters of the SPPE can be used to at least 8 hours. The UVGI is implemented by the use of UV LEDs. This implementation is done in two steps. Step one is a simulation which allows for the optimization of the LED placement depending on a multitude of parameters, including: distance between the LEDs and the filter, and the LED tilt angle. The second step is the design of a driver circuit, to allow for the adjustment of the dose applied by the LEDs. The simulation resulted in an LED array which offers the most optimal irradiation of the filter surface. The driver circuit has been designed, simulated to verify its functionality, and implemented in the form of a PCB design. The UVGI subsystem provides the SPPE with an in situ disinfection system by delivering a base dose of 305 mJ/cm2 and a driver circuit which allows for adjusting this dose, should this be desired. The UVGI subsystem should be able to extend the period in which the filters of the SPPE can be used to at least 8 hours. However, due to the restriction of not being allowed to create a prototype this has not yet been verified. ... Read more

The COVID-19 pandemic caused a shortage of Personal Protective Equipment for Healthcare personnel. This project aims to aid in this shortage by extending the lifetime of the filter material used in a mask. This is done in the form of an SPPE, a Smart Personal Protective Equipment. This face mask has two smart filter heads that are modular and contain UVC LEDs to disinfect the filter, a control system to control the LED's radiative power and an on-board power management system. The latter is the focus of this thesis.

The implementation of an on-board power management system for a smart personal protection face mask was designed in three stages: (1) researching existing theory about battery management, (2) implementing and verifying a system design in Simulink and (3) making a PCB design and selecting off-the-shelf components. The goal of this thesis is to make a complete design of a functional battery management system, that supplies required power to the rest of the system, ensuring safe battery operation and aiming to maximize battery life. In this, the design has succeeded as almost all requirements are met. The result is a PCB design that can be made and combined with two other subgroups to create a Smart Personal Protection face mask. The main findings were a different and possibly new approach to estimating the State of Charge of a battery and designing a Battery management system for low power applications in a small form factor as opposed to battery management systems for electrical vehicles, which are common today. ... Read more

The objective of the project is to design a system which can control the temperature of a va-porizing liquid microthruster (VLM). The liquid in a VLM is heated using a heater resistor.This resistor will be used to both heat the liquid and measure the temperature.In this thesis the subsystem responsible for the measurements and the conversion of the mea-sured signals to the digital domain will be discussed. We propose a method where short measure-ment current pulses of a fixed amplitude are applied to the heater resistor. As an optimization,these pulses are omitted when a certain current threshold has been met.Results show that the system can measure temperature with±1◦C accuracy, however more fullsystem measurements are required to ensure functionality as a whole. ... Read more

The goal of this bachelor thesis is to develop a control system that controls the temperature of a microthruster. This system also needs to acquire data for research. The microthruster contains a resistor that is used both as a heater and as a sensor. To facilitate the acquisition of data and the testing of the control system, a lab setup with a Keithley 2450 SourceMeter power supply was used. LabVIEW was used to control the power supply and to execute the control algorithms. The final system consists of a microcontroller that runs the control algorithms based on proportional-integral-derivative (PID) control developed in this thesis. The PID values can be adapted with use of the graphical user interface (GUI). A read-out circuit and current supply will be part of the integrated system. These circuits will be developed by other groups that are part of this bachelor project. ... Read more

This thesis presents the design of an accurate current source for MEMS vaporizing liquid microthrusters. An analysis of different power supplies is presented. The design choices leading to the implemented current sink topology is given. The main components, which are an op-amp, a MOSFET and a resistor, are analyzed extensively. System integration tests showed that the current source worked adequately. The current source has also been tested separately and the imposed accuracy requirement is not met. The reason for this has to be further investigated, as there are many potential sources of errors which can cause deviations in the order of microampere. Lastly, several recommendations are given for improving the system. ... Read more

Demand and development in the space industry are conditioning more costeffective satellites without a reduction in functionality. One of the means of satisfying thus requirements is miniaturization. Constructing, smarter, lighter and cheaper satellites to reduce the cost of delivering it to the orbit as the main chunk of mission cost falls on delivering the satellite to space. Lighter versions of satellites called nano-satellites (CubeSats) which could be fabricated in mass scale in a reproducible manner might be a suitable solution. In simple words nanosatellite is a state of the art device packed with advanced logic electronics, sensor and actuator arrays as well as power management systems, etc. to perform numerous tasks. Considering the already high cost for large scale integration of various components it is very important to extend the lifetime of the devices as much as possible. Beside radiation which is one of the main reason for the failure of the components, satellites are useful only if they remain in the orbit and not deviate from the specific path it was set due to drag. Therefore the propulsion system is required to control the altitude to increase the operational lifetime of the satellite. The project is a continuation of the work in realizing a new generation of noble green Vaporizing Liquid Micro Thruster (VLM) functioning in environmentally friendly propellant(water) fabricated in Else Kooi Laboratory (EKL) with the cooperation of Aerospace Engineering (AE) faculty with an intention of contributing to the DELFFI mission. Thesis includes fabrication and testing of a thruster with a heavy emphasis on improving the performance of the heating chamber. Fabrication was accomplished by designing modules separately and assembling them through part by part exposure in the lithography. Such an approach was taken due to the need for systematic analysis of numerous factors affecting performance by altering them and observe the effect on performance. Several heating chambers were designed with varying performance attributes and tested on its ability to deliver heat efficiently as well as affect to thruster performance like pressure drop. In addition to it, several fabrication techniques not used previously for the fabrication of thrusters were experimented and implemented on making various channel structures giving freedom of more 3D design. As a result novel type of Microelectromechanical Systems (MEMS) VLM heating chambers were fabricated by modular design and tested. Developed process is robust and flexible which allows to manufacture different types of VLM thrusters depending on operation demand and suited for integration. The novelty introduced in the project is step-wise heating as well as the application of a new type of localized heating chamber with improved geometry for enhanced heating efficiency and for wall temperature measurements. ... Read more