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.

Currently, EEG recordings are mostly made using scalp recording devices. These devices are typically difficult to put on and bulky, limiting their use to a lab environment. In-ear EEG recording is proposed as a more practical alternative to scalp EEG recording. In-ear EEG replaces the scalp electrode array with more discrete earpieces, recording the EEG signals from the ear canal instead of the scalp. Because of their increased convenience with respect to their scalp electrode array counterpart, the earpieces allow for everyday use, enabling the possibility of long-term EEG recording, outside of a lab environment. This work presents the design of a fully-integrated in-ear EEG device. The device has been designed to record EEG signals, process them locally, and transmit the processed data to a smartphone or personal computer. The device is made to be easily re-programmable, making it possible to change the device firmware depending on the intended application. This functionality has been integrated into a small form factor, to allow for the integration of the electronics into an earpiece. A low-power design has been created, to allow for long-term battery operation. Two prototypes have been made. The first prototype focuses on exploring different system configurations, with the small form factor less of a priority. The performance of the prototype is tested by comparing it to a commercially available scalp EEG recording device based on scalp EEG recordings. For this comparison, the auditory steady-state response (ASSR), steady-state visual evoked potential (SSVEP), and alpha-band modulation paradigms are used. The prototype has shown similar performance to the scalp EEG device in these experiments, with the scalp EEG device performing slightly better for the ASSR and alpha-band modulation paradigms, while the prototype showed the best performance for the SSVEP paradigm. The second prototype realises the best-performing system configuration that has been found with the first prototype into a form factor that fits into an earpiece. Ear EEG experiments are performed, with electrodes placed around the ears. The ASSR, SSVEP, and alpha-band modulation paradigms have again been used in these experiments. The measured performance on the ASSR and alpha-band modulation paradigms are slightly worse than that measured using the scalp EEG experiments. The SSVEP experiments showed significantly worse performance compared to the scalp EEG experiments. These results align with the expectations, as ear EEG has been documented to have performance close to scalp EEG for the ASSR and alpha-band modulation paradigms, while the SSVEP performance is typically worse for ear EEG than for scalp EEG.

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.

Current stroke treatments are limited to acute phase management, and there are few clinically available drugs for neuron protection or damage repair due to restrictions imposed by the blood-brain barrier. This project envisions an implantable DDS for precise drug dispensing to areas of the brain affected by stroke, using light-activated liposomes and microfluidic control to improve therapeutic effectiveness and minimize off-target side effects. Reviewing literature on microfluidic trap-and-release mechanisms, it became evident that deformable particles often tend to slip out of traps. To accurately predict this behavior, the Young's-Laplace equation and energy stored in the liposome membrane have been assessed. Next, microfluidic devices that were able to manipulate the liposomes to the desired trapping locations were designed and produced. The trapping behavior of liposomes has been assessed by increasing the hydrostatic pressure under a fluorescent microscope. The results show that the experimental pressure of 50-250 Pa is lower than the expected theoretical predictions and that there exists a diameter threshold of 17-18 μm for which the liposomes show lysis behavior. Finally, the entire DDS concept has been demonstrated using a network of traps using the path-of-least-resistance approach.