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This thesis describes investigations into the optical and device design of organic light-emitting diodes (OLEDs) with the aim of exploring the factors controlling the spatial emission pattern of OLEDs and developing novel OLEDs with directional emission by applying wavelength-scale photonic microstructure. The development of directional OLEDs was broken down into two steps: the development of efficient narrow linewidth OLEDs and the integration of wavelength-scale photonic microstructures into narrow linewidth OLEDs. The narrow linewidth OLEDs were developed using europium (Eu) complexes. The electrical optimisation of solution-processed Eu-based OLEDs using commercially available materials was investigated. The optimised Eu-based OLEDs gave an external quantum efficiency of 4.3% at a display brightness of 100 cd/m². To our knowledge, this is the highest efficiency reported for solution-processed Eu-based OLED devices, and the efficiency roll-off has been reduced compared with other reported references. Photonic microstructures were applied to develop directional OLEDs using the efficient Eu-based OLEDs. Two contrasting strategies were used. One was to embed photonic microstructures into Eu-based OLEDs, the other was to couple photonic microstructures externally onto the devices. The microstructured devices developed by the former strategy boosted the emitted power in desired angles in both s- and p-polarisations and doubled the fraction of emission in an angle range of 4⁰. The devices developed by the external coupling strategy achieved even higher directionality and the out-coupled emission was a confined beam with easy control of beam steering. Around 90% of the emitted power was confined in an angular range of 20⁰ in the detection plane. The optical properties can be optimised independently without compromising the electrical properties of devices, which gives major advantages in terms of effectiveness and versatility. Optical models were also developed to investigate the out-coupling mechanism of various trapped modes and develop OLEDs with stronger directionality.

The InsulPatch is a novel integrated patch-pump device used to deliver drugs, especially macromolecular drugs that are difficult to deliver through an oral pathway and that require transdermal delivery. The patch-pump is a promising replacement for conventional syringes and battery-powered pumps because it is slim, powerless, painless, and relatively inexpensive. The majority of this thesis focuses on the fabrication and testing of microfluidic devices for the delivery of insulin, which is a model drug that is widely used and needs to be delivered transdermally. In this thesis, we demonstrate the fabrication of the patch-pump, which includes an insect-mimetic microfluidic pump fabricated using photolithography and replica molding, and a microneedle array fabricated using 3D printing. The microfluidic pump is used to drive the fluid flow powered by pressurized air or the user’s pulse, and the microneedle array is used to inject the fluid through the skin painlessly. Using pressurized air-driven flow testing, we have tested the flow rate across microfluidic pumps of various flow channel widths over a range of physiologically relevant actuation frequencies and pressures. We have found that for the specific channel design we have been using, the flow rate generally positively correlates with the actuation pressure. For devices with wider flow channels, the flow rate generally negatively correlates with the actuation frequency, whereas the flow rate increases and then decreases with increasing actuation frequency for devices with narrower flow channels. This property of these devices is beneficial in insulin delivery because the demand for insulin is generally reduced in vigorous exercise (with elevated heart rate/actuation frequency) and increased in hypertension patients (with elevated blood/actuation pressure). A major future direction of the study is to test a wide range of device designs in a sample of human subjects by attaching the device onto the wrist and measuring the pulse-driven flow across the device. We can further change the channel design parameters of the device so that it will be ideal for insulin delivery. Using the ex vivo flow testing and human subject data, we can further tailor the device design to specific patients using a genetic algorithm-guided optimization based on the heart rate and blood pressure of the patient and the desired flow rate. We will also perform computational modeling using COMSOL Multiphysics to predict the flow across devices of different designs as well as to understand the physics behind the pulse-driven flow. Finally, a 3D-printed insulin reservoir will be incorporated into our patch-pump system for the storage of U-500 insulin.

Abstract: Under the impact of global warming, the hydro-climatology over the Arctic has changed significantly. Warming over the Arctic region is twice the global mean warming rate since the 1980s, known as Arctic Amplification, which occurs because warming induces melting of sea ice, leading to feedbacks that accelerate the ice loss, such as the ice-albedo feedbacks, water-vapor feedbacks, cloud feedbacks, and lapse-rate feedbacks. The rapid increase in air temperature leads to substantial decline of Arctic sea ice and more intensive hydrologic processes in the pan-Arctic river basins. As the primary freshwater source to the Arctic Ocean, streamflow from the pan-Arctic river basins plays a crucial role in the sea ice formation, oceanic circulation, and the thermohaline balance in the Arctic. With a warmer atmosphere, the melting season of sea ice has lengthened and the ice cover has become younger and thinner, while the streamflow from pan-Arctic river basins have shown an increasing trends in recent years. Numerous studies detected the teleconnections between the decline in Arctic sea ice and climate patterns, and the feedbacks, but the focus of these studies was more about average changes and the effects of individual climate patterns instead of their combined impacts. In addition, partly because of limited observed hydro-climatologic data available in pan-Arctic river basins, there have been relatively few studies on hydrologic responses of pan-Arctic river basins to climate change impact compared with studies in southern, highly populated regions. This dissertation began with an investigation on the decline of Arctic sea ice using a quantile regression method at all quantile levels. Next, hydrologic responses of the pan-Arctic river basins, such as non-stationarities and trends, and changes in wet and dry spells were analyzed by statistical and probabilistic analysis, and an artificial neural network. Therefore, the objectives of this dissertation are: (1) to analyze changes of Arctic sea ice under the possible impacts of climate patterns and the physical mechanisms behind the teleconnection with climate patterns; (2) to identify non-stationarities and trends of streamflow from three Great Siberian river basins using statistical analysis; (3) to simulate the streamflow of four large pan-Arctic river basins with machine learning models and to project hydrologic impact of climate warming to these pan-Arctic river basins; (4) to analyze the probabilistic characteristics of the duration and temperature of both wet and dry spells of the Siberian river basins, and the joint and conditional probabilities of extreme dry and wet spells occurring in these river basins estimated from a Copulas function.