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.

Flexible wearable sweat sensors can monitor sweat continuously and non-invasively in real time. They give useful information about the human body at the molecular level. Because of their high performance, low cost, and small size, electrochemical sensors have received much attention for use in personal health monitoring.

In this thesis, a back-end electronic system for a flexible electrochemical sweat sensor is developed with several key modules for stable and accurate monitoring. The work begins with a review of recent studies on wearable sweat sensing, focusing on ion-selective electrodes, iontophoresis, impedance measurement, and system integration methods.
Then, the overall system design is introduced, including schematic and layout planning, and main circuit blocks such as power management, iontophoresis for sweat induction, and impedance measurement using the AD5933 chip. Firmware and data collection with an STM32 microcontroller are also described, covering signal sampling, impedance readout, and Bluetooth communication.

The experimental part presents the validation of the first prototype, showing the main functional tests, the problems found, and their solutions in the second-version PCB. The MCU, power management, Bluetooth communication, and iontophoresis modules operated reliably, while the ISE readout and impedance measurement using the AD5933 were only partially successful. The second-version PCB is built on a flexible polyimide substrate with local stiffeners, forming a ridge-flex bridge structure. This design improves both mechanical strength and flexibility for wearable use.

Each year, stroke claims about 5.5 million lives and leaves around 116 million with lasting disabilities. Current stroke treatments focus on the acute phase, lacking drugs for neuron protection or damage repair due to the blood-brain barrier. This proof-of-concept project presents an implantable drug delivery system (DDS) using microfluidics and light-sensitive liposomes for post-stroke treatment in the affected regions of the brain. This research investigates the synthesis, characterization, and application of giant unilamellar vesicles (GUVs) for potential drug delivery applications. Vesicles synthesized by the gel-assisted swelling method. Dye encapsulation studies identified 5 μM as the optimal concentration, with higher concentrations negatively impacting vesicle formation. Stability assessments showed that PEGylation and cholesterol enrichment improved thermal stability and encapsulation efficiency, with lower temperatures generally enhancing stability. Coating GUVs with gold nanoparticles faced challenges with aggregation, indicating the need for optimized reagent concentrations and reduction processes. Dye release studies demonstrated stable encapsulation up to 39°C, suggesting potential for controlled release via surface plasmon resonance. Pipetting was found to better preserve vesicle integrity in microfluidic platforms compared to syringe introduction. Overall, this thesis provides comprehensive knowledge about the synthesis, lipid formulation optimization, and stability of GUVs, offering practical insights into their handling and application in microfluidic platforms, and laying the groundwork for future innovations in drug delivery systems.

In microfluidics, typical laboratory processes can be condensed to a miniature device. This reduces analysis time and required volumes of samples and reagents, increases mobility and flexibility, and is cost effective. In this work, the environmental impacts of three microfluidic devices for glucose detection are assessed using a comparative life cycle assessment (LCA) from cradle-to-grave. The three devices are a polydimethylsiloxane (PDMS) device manufactured through soft lithography, a paper device manufactured through wax stamping, and a polylactic acid (PLA) device manufactured through 3D printing. The environmental impacts are determined for two manufacturing scenarios: on laboratory-scale and commercial-scale. The functional unit is 1 act of glucose detection performed on a human sample using 1 microfluidic glucose detection device.
Assuming laboratory-scale manufacturing, the paper device has the lowest environmental impacts, whereas the PLA device has the highest impact. The main contributing processes are those pertaining to the devices' manufacture. For the PDMS device, these are the processes for soft lithography, for the paper device it is the paraffin use, while for the PLA device it is the 3D printing. Assuming commercial-scale manufacturing, the PLA device has the lowest environmental impact, whereas the PDMS device has the highest impact. This scenario was modelled by improving efficiencies in the manufacturing of the PDMS and paper device, and substituting 3D printing for injection moulding for the PLA device.
To reduce the devices' environmental impacts, a general recommendation is to transition to an electricity mix based on renewables rather than fossil fuels. For the PDMS device, a recommendation is to redesign the device such that the user can apply reagents before use, thereby avoiding emissions by cutting out a need for refrigeration, which is present in the current design. For the paper device a recommendation is to minimise the waste of paraffin, as it is the main contributor to the device's environmental impacts. Lastly, for the paper and PLA device it is recommended to consider alternate manufacturing methods when upscaling production. Their current manufacturing methods are ideal for prototyping, but are inefficient on a commercial scale.
Some limitations are that several data points were estimated, cut off, or secondary. Data gaps were bridged through the use of proxies and stoichiometry for chemicals, which affected the accuracy of the model. Furthermore, recycling and chance of failure during manufacture are not accounted for. Lastly, as microfluidic devices are designed in many different ways, the results cannot be translated one-to-one to other devices. They can only provide a general idea of what the impacts for other devices might be.
A continuation of this work could simulate the synthesis of chemicals using process design software, for increased accuracy. Another opportunity for further study is to collect and implement primary data and assess how that affects the results. Future research could investigate fields of microfluidics other than diagnostics. Generally, more research is necessary to model a proper ex-ante LCA with various scenarios. With enough research, microfluidics might fully reach its potential, while being environmentally responsible.

In-ear EEG is a discreet and convenient method for monitoring EEG by placing the electrodes in the ear canal. This enables everyday monitoring outside of clinical environments in contrast to generally used scalp EEG with wet electrodes. This thesis proposes and describes the design of novel flexible dry CNT/PDMS electrodes with short pins, long pins, and a snake pattern. These dry electrodes make use of microstructures to improve electrode-skin impedance (ESI) by enlarging the effective contact area. In the composite fabrication process, SEM is used to optimize CNT dispersion which plays a significant role in the impedance of the material. The performance of the proposed dry electrodes is evaluated in comparison to conventionally used wet Ag/AgCl electrodes. Electrode impedance measurements show the superior performance of CNT/PDMS electrodes with microstructures with lower aspect ratios. This is confirmed by ESI measurements, which show a 49 % improvement at 10 Hz for the electrode with short pins compared to the electrode with long pins, and a further 53 % improvement for electrodes with the snake pattern. This makes the latter comparable to wet electrodes. Moreover, normalization by the projected surface area shows significantly lower ESI at low frequencies for dry CNT/PDMS electrodes with a snake pattern compared to wet electrodes. ESI of the dry electrode at 10 Hz is 30 kΩ cm2, one order of magnitude lower than for wet electrodes. At 1 kHz the ESI is 9.9 kΩ cm2, which is comparable to wet electrodes. Finally, ASSR tests show comparable suitability of dry CNT/PDMS electrodes and wet electrodes for in-ear EEG monitoring, suggesting that the proposed dry CNT/PDMS electrodes are a viable solution for in-ear EEG applications.