In the field of Organ-on-Chip research, there is a strong demand for automated and scalable systems for muscle excitation and contraction measurement. This thesis presents an improved twenty-four-well system that utilizes Hall sensors to determine muscle contraction force. Building directly on an initial proof of concept, this work focuses on improving the cantilevers, the well design, and the printed circuit boards.

Furthermore, the amplifier was redesigned to accommodate the new system architecture, and a higher-resolution analog-to-digital converter was selected to improve measurement accuracy. The system can be controlled and monitored through a USB connection, enabling automated measurements, data visualization, and individual well selection.

Muscle excitation is provided through a square-wave stimulation signal with configurable amplitude, frequency, and duty cycle within commonly used stimulation ranges. As long-term biological testing is essential, the system was also designed to operate reliably within an incubator environment. ... Read more

High-mobility hydrogenated indium oxide (IO:H) thin films were developed, and the influence of post-deposition treatment on their opto-electronic properties was investigated. The IO:H films were deposited by magnetron sputtering and subsequently annealed using Rapid Thermal Processing (RTP), involving short exposure to temperatures between 400 and 700 °C. After annealing, the electron mobility of the IO:H films reached 146 cm²/Vs, demonstrating the effectiveness of short high-temperature annealing compared with conventional longer low-temperature annealing processes.

Transparent conductive oxides (TCOs) can reduce electrical and optical losses in crystalline silicon (c-Si) solar cells with Tunnelling Oxide Passivating Contacts (TOPCon). Therefore, this study examines how IO:H deposition and post-deposition treatment affect the passivation quality of these contacts. Deposition of IO:H on symmetrically passivated c-Si wafers significantly degrades passivation due to particle bombardment, which breaks Si–Si bonds and introduces defect states. Part of this degradation can be recovered through post-deposition annealing. Reducing the sputtering power density proved essential for mitigating passivation damage; a maximum power density of 0.62 W/cm² minimizes degradation and enables substantial recovery during annealing. However, due to dopant in-diffusion within the contact structure, the annealing temperature must remain below 550 °C.

Cox–Strack measurements of symmetric TOPCon/IO:H contact stacks show relatively high contact resistivity, primarily caused by oxygen adsorption when IO:H is deposited at low power density. This leads to the formation of an electron barrier, limiting the field-effect-driven mobility of electrons traveling from the contact into the TCO. Reducing both the thickness and carrier concentration of the IO:H buffer layer is therefore important for lowering the contact resistivity. Literature further indicates that inserting a thin indium tin oxide (ITO) interlayer between IO:H and silver can significantly reduce contact resistivity and improve overall solar cell performance. ... Read more

Wearable technologies enable non-invasive and continuous monitoring of physiological parameters offering cost-efficient alternatives to clinical assessments. Among them, sweat sensors expand the available biometrics by providing access to biochemical information. Analyte concentrations in sweat vary substantially with inter- and intra individual differences in sweat rate (SR). Therefore, sweat sensors need to measure SR to deliver reliable data. This work presents the design and development of a microfluidic SR sensor for continuous monitoring in a skin patch. The device uses electrodes patterned on polyimide and embedded within polydimethylsiloxane (PDMS) microfluidic channels to quantify SR by tracking fluid progression through impedance measurements. Two electrode materials, thin-film gold electrodes and laser-induced graphene (LIG) electrodes, were investigated for this application. Gold electrodes showed a more stable SR sensing performance demonstrating high sensitivity across physiologically relevant SRs, ranging from values typical at rest (0.2 µL/min) to physical exercise (5 µL/min). Additionally, the sensor maintained a stable performance under mechanical deformation as well as during on-body testing. This supports the sensor’s suitability for wearable applications. The sensor response was also evaluated across electrolyte concentrations (10-100 mM) and temperature variations (20-40 ºC), highlighting the need to include calibration strategies that can compensate for these effects. The proposed sensor architecture was designed to be compatible alongside ion-selective electrodes, for sodium and chloride sensing, to support future incorporation into a complete wearable sweat analysis platform. ... Read more

Over the past two decades, Organ-on-a-Chip (OoC) technology has advanced significantly, and with the recent shift by the FDA toward favouring this technology over traditional animal testing for drug development, research in this field has accelerated. At TU Delft, this research continues with a focus on Gut-on-a-Chip (GoC) systems. Building on the earlier work of Tawade et al. on a silicon-based tissue-barrier-on-a-chip, and in line with the long-term goal of developing a multi-sensor integrated GoC, the present work focuses on the development of a silicon-based spatial transepithelial electrical resistance Gut-on-a-Chip (s-TEER GoC).
The “spatial” aspect refers to the ability to obtain localised TEER measurements through the integration of multiple 4-point electrode setups within the GoC design. A novel feature of the s-TEER GoC is the introduction of current windows, which guide and focus the current density fields generated by the electrode setups to specific regions of the tissue barrier. In addition, the chip design has been optimised to require only one-sided fluidic access, enabling compatibility with a standardised multi-organ-on-a-chip Translational OoC Platform (TOP) module developed by Yeh et al. This is achieved through the implementation of two vertically-stacked Z-shaped microfluidic channels, inspired by previously-reported polymer-based designs.
In this work, detailed design parameters were established to meet both the microphysiological modelling and biosensing requirements of the chip, using a theoretical framework and COMSOL simulations to analyse fluidic, mechanical, and electrical performance. A large part of the fabrication of the s-TEER GoC was carried out using microfabrication techniques available at the Else Kooi Laboratory on the TU Delft campus. In addition, a PCB and microfluidic packaging were developed to connect the chip to external fluidic and electrical control and measurement systems in a standardised way. Results include the executed fabrication steps and preliminary validation of the mechanical, optical, and fluidic functionality of the device.
This work demonstrates the feasibility of a silicon-based Gut-on-a-Chip platform with spatially resolved TEER sensing, providing a foundation for future development of multi-sensor integrated systems. The s-TEER GoC represents a step toward more physiologically relevant, high-resolution in vitro models, supporting the ongoing transition away from animal models in preclinical research. ... Read more

This report presents the design and implementation of a single-well muscle-on-a-chip device capable of displacing one of the support pillars to which muscle tissue is bound, using an electromechanical actuator. In addition to this displacement capacity, the muscle tissue can be electrically stimulated, allowing for the measurement of corresponding contraction forces via post-deflection methods. Experimental results demonstrate that the actuated support pillar can be moved by approximately 40μm per
step. ... Read more

In the field of Organ-on-Chip research, there is a desire to have an automatic and scalable system for muscle excitation and contraction measurement. In this thesis, the CHAMP is introduced, a 24-well system that uses magnets and Hall sensors to determine the deflection of cantilevers on which muscles are seated. The CHAMP allows for simultaneous four-channel measurements with a resolution in the micro-Newtons and milliseconds. The entire design can be put in an incubator, is biocompatible and 3D printed from rigid and flexible resins. The system can be read out and controlled via USB connection, with custom programs in CSV format for simple and automatic measurements. The excitation is a square wave, with variable parameters for duty cycle, frequency and amplitude in the common ranges. Future designs should replace the cantilever material to reduce nonlinearity and manufacturing problems, and improve the ADC resolution to enhance measurement accuracy. ... Read more

The airway epithelium plays a crucial role in respiratory defense by regulating cellular composition and related functions to maintain pulmonary homeostasis. This study investigates the impact of temperature variations (33°C and 37°C) on cellular differentiation, mucociliary function, and host defense responses of human primary bronchial and nasal epithelial cells (hPBECs and hPNECs) cultured at the air–liquid interface.

A reduction in temperature from 37°C to 33°C significantly increased goblet cell-related gene expression (MUC5AC) while decreasing ciliated cell-related gene expression (FOXJ1). Mucociliary clearance was generally impaired at 33°C, with ciliated cells displaying less organized ciliary alignment; however, donor variability made it challenging to establish consistent trends. Furthermore, cultures maintained at 33°C exhibited an enhanced antiviral response to Poly(I), as indicated by increased IFNL gene expression in both bronchial and nasal epithelial cells. In contrast, temperature had no effect on the inflammatory response to whole cigarette smoke in bronchial cultures but attenuated the oxidative stress response in nasal cultures, as evidenced by reduced HMOX1 expression at 33°C.

Analysis of Notch signaling revealed no significant alterations in the expression of key target genes (HES1, HEY1), with the exception of a transient decrease in HEY2 at 33°C, suggesting complex regulatory interactions.

These findings support the hypothesis that the temperature gradient along the airway tree influences the spatial distribution of airway epithelial cells, with potential implications for airway remodeling in chronic lung diseases such as asthma and chronic obstructive pulmonary disease. However, further studies are needed to confirm these results and explore their clinical relevance. ... Read more

The ability to quantify ion transport in a dielectric is of major interest for the development of reliable biomedical devices. A novel and scalable method for accomplishing this is established in this thesis. As ions from the gate of an electrolyte-gated field-effect transistor (EGFET) ingress into the gate dielectric, they induce a charge in the channel. The developed method works by replacing the gate dielectric with a layer under test (LUT), measuring the induced charge, and relating it to ion transport parameters. Scalability is achieved with a silicon-based sensor die on which the LUT can be deposited and an easy-to-use experimental setup. Four different EGFET devices and an integrated biasing technique are incorporated on the die to ensure functionality across a wide range of LUTs, ion species, and experimental conditions. Based on a drift–diffusion transport model, a novel working model was developed, which enables extraction of ion diffusion coefficients independently of experimental conditions. Together, the sensor, setup and model form a versatile and scalable platform for studying various combinations of LUTs and ion species. ... Read more

In-vitro 3D organoid cultures constitute an essential component of modern-day biological research, with key application areas in drug and therapy testing, and Organ-on-a-Chip models. The increasing demand for reliable models comes with the challenge of boosting the throughput of production of these cultures. The currently researched 3D culture methods pose the challenge of not being contact-free, of limited versatility and throughput in organoid culturing, and often lack a stimulus to promote cell agglomeration. This work presents acoustofluidics as a stimulus-driven solution to promote the clustering of cells in a levitated, suspended environment. In order to establish this objective experimentally, an SBAW resonator was designed, fabricated, and tested as a PoC (Proof-of-Concept). The experiments were carried out with the fabricated PoC which was characterized to assess the trapping performance and determine the controllable experimental variables to tune the acoustofluidic effects aptly, leading to the formation of stable clusters in SBAW nodal planes. On successful fabrication, the device showed repeatable trapping over a wide bandwidth of 300 kHz, and trap stiffnesses of up to 1.7 fN/μm determined experimentally based on the processing of particle agglomerate imaging. It was observed that the trap stiffness was adequate for levitation over several hours, and yet allowed for the formation of a 3D agglomerate of particles. It was also shown that a frequency-sweep actuation was successful in overcoming fabrication limitations and suppressing streaming, and a suitable working range of experimental parameters could be determined to achieve initial clustering in under 3 minutes. A futuristic outlook on the in-plane particle confinement methods to further improve the target performance, and considerations for biological experiments as the immediate next step have been presented as a concluding note in this thesis. This work thus paves the way for the integration of this technique into laboratory organoid culture formats. This positively complements the objective of cutting down the agglomeration time for initial organoid clustering, for an anticipated positive impact on the production throughput and developmental aspects of organoid cultures, with the in-house fabricated and characterized PoC presented in this work as an enabler. ... Read more

This report presents the design process of a project aimed at the automatic recognition of 3D structures formed by magnetic spheres in a turbulent water-filled cylinder. This field of research holds promise for future technologies, as macroscopic self-assembly might be the key to three-dimensional storage on chips. With the macroscopic setup, the microscopic self-assembly process is imitated. To automatically recognise a 3D structure, this report is divided into three subgroups that research the optimal test setup, develop an image processing program and create a deep learning model. A labelled result of the 3D formation will be outputted, all while limiting the data size, computation time and inaccuracies. The subgroup responsible for the setup and the underlying physics produces images of the magnetic spheres forming a structure in the test setup. The Image Processing subgroup extracts the properties of the spheres from the image. Finally, the subteam for deep learning, in combination with data management, gives the extracted properties as input to a neural network model, which determines the structure of the spheres. Each submodule has demonstrated successful functionality on its own. However, due to time constraints, a fully integrated system with high accuracy has not been achieved yet. Future work will involve expanding the dataset to enhance the robustness of the recognition algorithms. ... Read more

This report entails the design process and development of an RFID (Radio Frequency Identification) system that must serve as a user interface for a surgical tool developed by SLAM Orthopedic. The goal of the user interface is to allow a surgeon to make selections as input for the surgical tool. The RFID interface is specifically designed to fit into the device, which leads to several design constraints like power consumption and size. The RFID system uses a coil antenna which was tuned for a specific frequency with the help of a Vector Network Analyser and Smith Charts. A prototype for the system was made but not finalised, however, results of the tuning process and research on RFID technology showed that an RFID system could be a promising interface for this surgical tooling. ... Read more

This report entails the design process and development of a rotational ring system that must
serve as an user interface for an existing system, the ADEPTH. The goal of the rotational ring is to allow a surgeon to make selections in the user interface system. After careful consideration of the provided list of requirements, it was decided to use changes in magnetic fields, sensed by a Hall sensor. This Hall sensor detects whether an external ring was rotated to the left or to the right. The inside of the ring contains six samarium-cobalt magnets, chosen for their extreme resistance to demagnetisation at high temperatures. This was a consideration, because the magnets have to undergo repeated cycles of sterilisation as hot as 134◦ C. After iterated prototype testing, a final working prototype has been developed, which can communicate wirelessly with the user interface system and send ’left’ & ’right’ commands. This final prototype is watertight and low power, which satisfies two of the most desired requirements. ... Read more

Dielectric spectroscopy, a non-contact electromagnetic readout technique, offers significant potential in Organ-on-Chip devices for accelerating drug development by enabling non-invasive, multi-layer sensing of tissue barrier integrity. While open-ended coaxial probes are well-established for dielectric spectroscopy in high-loss biological samples, their inherent lack of biocompatibility and impracticality in conventional setups limits their application. This work investigates novel fabrication approaches using printed circuit boards (PCBs) and glass manufacturing techniques to overcome these challenges. A planarized OECP fabricated on a PCB with via-array shielded coplanar waveguides was developed and evaluated. The PCB-based design demonstrated satisfactory electromagnetic performance, biocompatibility potential, and cost-effectiveness, making it a promising candidate for integration into well-plate formats. Additionally, laser-induced deep etching (LIDE) was explored for creating high-precision glass substrates with metalized vias, presenting an alternative route for scalable sensor fabrication. Together, these advancements lay the foundation for adaptable and scalable dielectric spectroscopy platforms suitable for Organ-on-Chip applications, merging performance with practicality in biological settings. ... Read more

Heart diseases are the leading cause of death worldwide, which is why heart diseases have become an important focus for the development of new effective treatments [1]. However, the current drug development pipeline is fraught with inefficiencies, ethical concerns, and financial burdens, largely due to the reliance on animal models and static cell cultures that fail to accurately predict human physiological responses [2]. Building on previous work from Dr. Dostanic [3], this master’s thesis advances the development of a novel Engineered Heart Tissue (EHT) platform, which holds promise as a more accurate and ethical research model for studying biological processes, drug discovery, and heart disease mechanisms. The EHTplatform is a small PDMS-based construction and consists of two micropillars surrounded by an elliptic well. It also features co-planar capacitive displacement sensors, specifically designed to measure the contraction force of EHTs. This master thesis work focuses on optimizing sensor sensitivity and enhanc ing platform rigidity to prevent sensor damage during assembly of the platform. Using COMSOL Multiphysics simulations, ideal sensor geometries and substrate configurations were identified, leading to the design and fabrication of multiple sensor prototypes. The sensors were fabricated using microfabrication techniques and electrically characterized under static and dynamic conditions. While static capacitance measurements aligned with simulations, dynamic tests revealed discrep ancies between predicted and observed capacitance changes, indicating the need for further investigation into simulation accuracy and fabrication processes. Despite these challenges, the sensors showed promise by successfully measur ing platform displacement in response to applied forces. However, the platform’s sensitivity must be improved in order to detect EHT contraction. With continued advancements, this platform could contribute to the develop ment of more precise and ethical research models, ultimately accelerating the de velopment of new treatments and providing an alternative for the use of animals in research. ... Read more

Osteoarthritis (OA) is a degenerative multi-tissue disease of the articular joint, with abnormal loading considered as one of the risk factors. Current 3D in vitro models are limited by their inability to deposit neo-bone and neo-cartilage in interaction, while simultaneously allowing the study of mechanical loading on the osteochondral compartment. In this work, a microfluidic osteochondral organ-on-a-chip (OoC) model was redesigned and fabricated to study the effect of mechanical loading on the osteochondral compartment inside the microfluidic chip. Additionally, the effect of hyper-physiological loading on the shear modulus of chondrocyte pellets and its relation with anabolic cartilage markers ACAN and COL2A1 was investigated.
After successful fabrication of the microfluidic OoC model that enables application of consistent mechanical load onto the osteochondral construct inside the chip, an injurious hyper-physiological loading regime was applied. To accomplish this, a computational model was developed to correlate the elastic strain in the cartilage tissue construct with the indentation applied to the chip. Gene expression analysis via quantitative reverse transcription polymerase chain reaction (RT-qPCR) was used to assess the effects of this hyper-physiological loading regime on the chip and compared to mechanically loaded chondrocytes pellets. The presence of anabolic genes, ACAN and COL2A1, in the microfluidic chip, along with comparable levels of the cartilage homeostasis marker FRZB relative to the chondrocyte pellet model, indicated successful chondrogenesis inside the chip. Furthermore, significant upregulation of mechanical loading marker PTGS2 confirmed stress levels were achieved in the chondrocytes inside the chip model. Upon hyper-physiological mechanical loading, the chip model showed significant upregulation of ACAN, COL2A1 and FRZB 12 hours post-mechanical loading. However, in the pellet model, ACAN and FRZB were downregulated as a result of mechanical loading. Hyper-physiological mechanical loading also increased the shear modulus of chondrocytes pellets, with a significant effect observed 7 days post-mechanical loading. Furthermore, a positive correlation was found between COL2A1 expression and the shear modulus. This study demonstrates that the developed microfluidic OoC model can serve as a platform to test the effect of hyper-physiological mechanical loading of neo-bone and neo-cartilage in interaction. Future studies should enhance the model by improving the integration of the luers and bonding the microfluidic model to an incompressible material while exploring the effects of a more intense loading regime. ... Read more

Organs-on-Chip (OoC) has been an advancing biotechnological field for the last two decades. By combining engineering and biology, OoC technology makes it possible to mimic the in-vivo behavior of human organs to investigate personalized medicine and disease modeling in-vitro.
Integrating sensors into cell cultures is crucial since the well-being of the culture needs to be monitored in real-time and without compromising cell viability. Monitoring the pH level of the micro-environment is particularly important since it is an indicator of homeostasis for the cell well-being and products of cell metabolism can cause changes in pH, reflecting certain disease phenotypes.
In this work, the integration of electrochemical sensors into OoC devices was shown. The sensors are based on a floating-gate field-effect transistor (FG-FET), a variation of a common active electronic component, and are sensitive to local electric charge. The active component provides inherent amplification, which translates to higher sensitivity and resolution for smaller changes from segregated analytes. The FG-FET was capacitively coupled to two control-gates to determine the working point of the transistor. The sensing area (FG extension) was separated fromthe active FET area to ease the handling of analytes. When there is a net charge in close proximity to the extension of the FG, it induces a change in the formation of the channel of the transistor. This change can be monitored by the drain current.... ... Read more

The brain is the most intricate organ in the human body, yet the underlying mechanisms of its cells and networks are not fully mapped. In addition to this lack of understanding, there are numerous neurological disorders and diseases for which a cure remains elusive. There has been persistent research to understand how neuronal cells function when interfaced to engineered biomaterials. The mechanical, topological, and chemical features of the extracellular matrix influence neuronal cell growth, and, among these, also electrical cues play a fundamental role in steering cell fate. The importance of electrical stimulation and 3D engineered microenvironments, better mimicking the spatial configuration followed by cells in the natural brain tissue, necessitates therefore the design of electrically conductive 3D microstructures. In light of the limited number of 3D electrically conductive scaffold studies, their reproducibility issues as well as fabrication constraints, the aim of this thesis is to at develop 3D electrically conductive free-standing microstructures made of polymeric materials. To achieve this goal, a protocol involving the chemical oxidative polymerization of EDOT (3,4-ethylene dioxythiophene) into PEDOT, an electrically conductive polymer, is developed. To ensure conductivity throughout polymeric 3D microstructures, EDOT is incorporated into an acrylate-based resin (IP-L) and 3D printed via twophoton polymerization (2PP), a 3D printing technology with sub-micrometre resolution. The electrical conductivity is experimentally measured, and it is reported how the tuning of printing parameters and organic solvents have a significant influence, with a maximum conductivity of 17.43 S/m after Dimethyl sulfoxide (DMSO) treatment. The mechanical properties of the 2PP-printed structures are evaluated as well, highlighting that the stiffness of microstructures decreases as EDOT doping increases. The versatility of the developed approach is demonstrated by fabricating 3D cage matrices featuring geometries suitable for neuronal cell culture. The reported results pave the way to further investigate the effect of 3D electrically conductive PEDOT-doped microstructures on neuronal cell growth and development. ... Read more

A stage heater for inverted optical microscopy was developed as an add-on to TU Delft portable integrated microfluidic platform. The platform was modified to gain additional functionality and portability. The stage heater was designed to work with custom PDMS microfluidic chips and commercial polymer chips which highlights the adaptability of the setup. The on-off temperature control was evaluated via an external thermocouple sensor, and the standard deviation of temperature in the cell chamber did not exceed 0.3 °C. An intermittent flow mode (flow for 1 minute at 10 µl/min, pause for 10 minutes) was introduced to match the requirements of an experiment involving T-cell and tumour spheroid interaction. The stage heater was deemed compatible with fluorescent and transmission imaging modes for up to 20x magnifications when equipped with a PET ITO-coated bottom heater with a window underneath the cell chamber. An increase in T-cell activity was observed with enabled heating. The process of T-cells attacking a spheroid via a time series of images was captured. ... Read more

3D-multi-electrode arrays (3D-MEAs) are needed to overcome the limitations of 2D-multi-electrode arrays (2D-MEAs) and enable the electrical characterization of 3D neuronal cultures in in vitro brain models, advancing the understanding of neurological disorders and paving the way to personalized medicine. The aim of this thesis was to overcome some of the limitations of current 3D-MEA devices and develop structures approaching the stiffness of the brain microenvironment, by using materials softer than conventional Silicon.A polymeric 3D-MEA was designed and developed by means of an innovative combination of two-photon polymerization (2PP), a 3D printing technology with sub-micrometer resolution, and standard wafer-level microfabrication methods from the semiconductor industry. Two novel fabrication protocols were developed, the first being a combination of 2PP with high-aspect ratio photolithography, which, though feasible, proved to require an inconveniently laborious process flow. The second fabrication process employed instead 2PP to fabricate the polymeric structures, pattern the microelectrodes, and provide electrical insulation. The 2PP-based process flow was ultimately preferred due to its potential for fabrication of structures of higher aspect ratio and geometrical complexity for 3D-MEA, extending their measurement resolution. Furthermore, a wafer-level alignment routine was developed with an alignment repeatability of 2PP structures of ±5 µm, which enabled the multi-step 2PP fabrication process. A novel maskless photolithography via 2PP process was also developed to pattern thin films over slanted surfaces, utilizing photoresist and glycerol-based immersion optics. The resulting 3D-MEA consisted of 15 printed polymeric pyramids featuring a total of 60 gold microelectrodes. The electrical insulation of the traces was partially successful, and will require further process development.The results demonstrate the feasibility of merging, for the first time, the 2PP process with standard wafer-level microfabrication techniques, specifically for the fabrication of a 3D-MEA for in vitro studies of human induced pluripotent stem cell (hiPSC) neuronal cultures. The 2PP-based solutions provided in this thesis show a promising pathway for the development of more complex and biomimetic 3D-MEAs. More generally, the developed wafer-level alignment routine and maskless photolithography via 2PP process for high-aspect ratio structures contribute to advance the field of microfabrication, and may enable the development of other types of innovative microdevices. ... Read more