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.

As a novel alternative for conventional seed disinfection methods, a new design has been proposed in this report using a surface dielectric barrier discharge (SDBD) fractal electrode. The discharge mechanism for this electrode is a diffuse microdischarge under AC or short-pulsed DC mode operation. In this way, cold plasma could be generated that is applicable for seed disinfection. Furthermore, the electrodes were designed to be part of a proof of concept fluidized bed reactor with a reactor size of 10×20×20[𝑐𝑚] for disinfecting cabbage seeds with a diameter of 2𝑚𝑚. Because of this application, the efficacy of seed decontamination using plasma with its generated reactive agents was discussed. The used gas mixture in which the electrodes created plasma was ambient air without increased humidity. This means that the main reactive agents for sterilisation are reactive oxygen species (RON) like ozone (O3) and reactive nitrogen species (RNS). The electrical and physical parameters required to make cold-plasma were investigated to come up with a proper design for the electrode. From this theoretical analysis, five different initial designs emerged. The analysed designs include a wire-to-wire, wire-to-sheet, multi-hollow DBD, fractal SDBD and a coplanar DBD fractal electrode. All electrode designs were made based on the state-of-the-art dielectric barrier discharge principle. Moreover, in the design consideration, different materials for the conductor and dielectric were discussed, mainly based on electrical properties, plasma generation and manufacturing possibilities were considered. Based on previously set trade-off requirements, together with the results of measured power and turn on voltage of the plasma electrodes, the best designs tested design for seed disinfection are the double-sided 5𝑡ℎ order Hilbert fractal with a 1.6 𝑚𝑚 barrier and the single-sided 5𝑡ℎ order Hilbert fractal with a 0.8 𝑚𝑚 barrier.

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.

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.

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.

Small satellites require efficient propulsion systems for attitude and orbit control. This thesis focuses on the development and characterization of two distinct types of micro-resistojet thrusters, namely Vaporizing Liquid Micro-resistojet (VLM) and Low Pressure Micro-resistojet (LPM). Both concepts are developed at TU Delft and are designed to use water as a propellant, conforming to launch-safety, simplicity, and cost-effectiveness criteria.
In VLM, liquid water is vaporized and accelerated through a convergent-divergent nozzle. In contrast, LPM operates by reducing water vapor pressure to below 300 Pa and then accelerating it through expansion slots under a rarefied flow regime. Both types of thrusters are built on Micro-Electro-Mechanical Systems (MEMS) chips to accommodate the size constraints of nano- and pico-satellites.
The thesis introduces refined designs for both VLM and LPM thrusters. Specifically, the VLM design features an optimized nozzle shape and improved inlet flow, while the redesigned LPM assembly is more space-efficient. These modifications increase the thrust-to-size ratio for both thruster types.
The thesis presents a fabrication process for these thrusters, employing an anodic bonded silicon-glass wafer stack with a capped microfluidic channel. Fabrication was executed at the EKL lab, using a simplified manufacturing process that is detailed within the report.
Post-fabrication, the thrusters underwent mechanical and electrical characterization. The results indicate incremental improvements in both design performance and manufacturability. The new VLM design yielded a 15% increase in thrust efficiency, while the new LPM assembly reduced the occupied volume by 30%.

Board-level reliability (BLR) looks at the reliability problem in the package and PCB interconnection, which is an important topic in microelectronics. The current criterion in the BLR test is to look if the connection is open, which can only detect the failure and there is no available method that can detect the degradation of the solder joints. This project mainly focuses on the degradation process of solder joints in board-level vibration tests and thermal cycle tests.

Special methods and test programs are developed tailored for two test vehicles, and some of the test results are collected and analyzed. Assisted by the failure analysis technique, the physical change of solder joints can be observed.

Findings in this study show the parameter shift during the solder joint degradation and also the mathematic model that describes the relationship between the crack of the solder joints and resistance increment.

Airspeed information plays a crucial role in the takeoff, flight, and landing processes in animal flyers and aerial vehicles. Among the aerial vehicles, Flapping Wing Micro Air Vehicles (FWMAVs) represent the novel engineering approach of learning and mimicking animal flyers in the past two decades. A few prototypes of various sizes and functionalities of FWMAVs have been developed by MAVLab in the TU Delft Aerospace department since 2005. For these small and lightweight platforms, stable control under disturbances remains a challenge, and could further benefit from integrating effective airflow sensing into control system design.

Current commercial products are either not suitable due to size, weight, and power (SWaP) restrictions of the drone platform, or have very limited low-speed sensitivity. Therefore, to facilitate this, this thesis aims to develop a MEMS-based capacitive airflow sensor for a miniaturized and low-power implementation. Inspired by the filiform hair structure of arthropods, the sensor design comprises two key parts: the hair structure, whose displacement is governed by the drag force induced by the incident airflow, and the sensing base, located at the hair structure's base, which translates the structural displacement into a change in capacitance. The sensor exhibits the capability to sense airflow in one dimension and can be further adapted for omnidirectional sensing.

This thesis predominately focuses on the design and reliable fabrication of the sensing base. It is comprised of a suspended membrane supported by corner beams, supplemented by a pivoting dimple and anti-stitching dimples to facilitate robust hair movement and ensure optimal sensor functionality. The sensing base is fabricated at the TU Delft EKL cleanroom facility, equipped with sophisticated machinery that enables fabrication at micro and nano scales. Furthermore, the membrane suspension is achieved through the implementation of Vapor HF etching of a sacrificial layer beneath the membrane.

In conclusion, the devised sensors aspire to optimize flight control for FWMAVs within the constraints of SWaP, by drawing profound inspiration from the intricate workings of nature.

Today’s cars are undergoing the greatest transformation the industry has seen. Power MOSFETs play a crucial role in making electronics more energy efficient by driving down switching losses and Rdson using a combination of next-generation trench technology and ultra-thin dies. Power MOSFET dies are becoming larger ( > 5 X 5 mm ) and thinner ( < 50 μm ) to meet the high performance lifetime requirements of the automotive industry. The high aspect ratio and the new chip designs with trench technology offer challenges for assembly, packaging and testing.

The majority of the research performed in the past, aimed to reduce the risk of die crack by improving equipment and process strategies in back-end semiconductor processing. This thesis study aims at improving die
strength from a front-end approach (device fabrication process) by making dies stronger to stress from die frontside. New chip designs are presented with new metal layer layouts for improved stress distribution. Materials like polyimide are investigated as new die top material for mechanical strengthening of die frontside. Key factors which influence die strength like trench-metal interaction, wafer stress and warpage are also analyzed in this thesis report.

In this study, ultra-thin power MOSFET dies are realised on 100 mm diameter silicon wafers with dimensions of 6 X 3 X 0.050 mm. These dies are mechanical equivalent in design, robustness to commercial trench power MOSFETs. The processed wafers are grinded from the backside to realise 50 μm thin wafers which are then sawned to obtain singulated dies. The strength of the dies are characterized by three-point bending tests and analyzed using probability plots for weibull distribution.

This thesis investigates the all-copper fine pitch bonding process with photoimageable underfill. NanoCU paste is used as interconnect material. A bi-layer photo resist structure is manufactured and lithographic stencil printing is used to apply nanoCu paste. A new underfill injection method is realized by using epoxy resin based photo resist as underfill layer. Adhesion of sample is extensively enhanced. Various bonding methods are developed including using AML bonder and Tresky pick-and-place bonder. Electrical measurements for sintered nanoCu interconnect are conducted, sheet resistance and contact resistance are studied.

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.

Since the unravelling of the Covid-19 pandemic, studying methods of virus inactivation have become more important than ever. Many studies focus on the chemical and optical methods of inactivation. Very limited work has been carried out in studying the electrical methods of virus inactivation. The work presented in this thesis attempts to pioneer a study that examines the effect of electric fields generated by micro-electrodes on the survival of the surrogate of the SARS CoV-2 virus.
For this purpose, electrodes with 7 different geometries were micro-fabricated and characterized. A liquid suspension of the phi-6 bacteriophage (a surrogate of the SARS virus) was tested on all the different electrodes with different input voltages, frequencies and medium parameters.
The study showed that the treatment on specific electrode designs tailored with specific voltage and medium parameters showed a decrease in the virus titer ranging from half a log to a maximum of 2 logs. These results are promising for the development of products like electric facemasks, micro-filters and m-TAS systems.

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.

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.

Analyzing the different signaling pathways of cells is key in understanding the basic functions of the cells in all organic systems from algae to humans. Not only do they help solve our questions on how organisms function, they also allow for new cures to be explored. A large variety of these signaling pathways can be influenced by light and can, for example, stimulate or inhibit cell growth. This research thesis introduces a new lab-on-a-chip MEMS device to help with the cell signaling exploration with a focus on optical cell stimulation. From a culture of HeLa cells, the chip is able to separate individual cells into different chambers by means of microfluidics. These microfluidic channels are processed using SU-8 and place each cell above an LED. In total, each chip houses ten LEDs with four different wavelengths ranging from 450 to 850 nm. Each of these LEDs is individually addressable through an Arduino MEGA with a Matlab user interface. After an introduction into cell signaling, the thesis describes how the chip is build up from two silicon wafers and one glass wafer, and explores novel assembly methods like SU-8 wafer bonding and the use of apertures.

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.