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Biosensors are used for the detection of a range of analytes for applications in healthcare, food production, environmental monitoring and biodefence. However, many biosensing platforms are large, expensive, require skilled operators or necessitate the analyte to be labelled. Direct electrochemical detection methods present a particularly attractive platform due to the simplified instrumentation when compared to other techniques such as fluorescence-based biosensors. With modern integrated circuit capabilities electrochemical biosensors offer greater suitability for monolithic integration with any necessary signal processing circuitry.This thesis explores micro- and nanogap devices for both redox cycling and dielectric spectroscopy sensing mechanisms. By using two electrodes with interelectrode separation down to distances in the micro- and nanometre scale, several benefits can be realised. Firstly the close proximity of the two electrodes significantly reduces the interdiffusion time. This allows an electroactive species to be rapidly shuttled across the gap and switched between reduced and oxidised states. The result is feedback amplification of the amperometric response, increasing the signal. The second benefit is that the screening effect caused by electric double layers at the electrode–electrolyte interface is reduced due to the electric double layers occupying a larger fraction of the sensing volume. This significantly improves the sensor suitability for dielectric spectroscopy by increasing the potential drop across the biolayer.These two sensing mechanisms are demonstrated using a large area dual-plate microgap device for the detection of two different analytes. Utilising the first mode, detection of cysteine–cystine, an important redox couple involved in the signalling mechanism for the regulation of protein function, interaction and localisation is shown. The microgap device is then used for dielectric spectroscopy sensing of a mannose-specific uropathogenic Escherichia coli strain whilst also demonstrating the effect of ionic concentration on the capacitive response.The response of these devices is highly dependent on the interelectrode separation as well as the surface area of the electrodes. However, fabrication of large-area nanogap devices presents a significant challenge. This meant that careful optimisation and the development of novel techniques was necessary. This work reports the design, fabrication and characterisation of both a vertical and a horizontal coplanar large area nanogap device. The vertical nanogap device is fabricated using an inductively-coupled plasma reactive ion etching process to create a channel in a silicon substrate. A lower electrode is then optically patterned in the channel before anodically bonding a second identical electrode patterned on glass directly above. The horizontal nanogap device uses a different approach, utilising a state-of-the-art electron-beam lithography system to create a long serpentine nanogap with passivation to reduce fringing effects. The design allows the electron-beam lithography step to be substituted with nanoimprint lithography to reduce cost and improve throughput. Both of these devices have integrated microfluidic channels and provide a capacity for relatively high-throughput production.

This paper presents a new simulator platform with findings from experiments aiming to identify the electrical characteristics of a marine vessel covered in photovoltaic modules, operating in various sea conditions. More specifically, we show that by giving a solar array the ability to reconfigure the arrangement of its modules in real time, that significant improvements (up to 50%) in power yield can be achieved compared to typical static arrays. A bespoke MATLAB simulator has been developed in order to model the complex interplay between the electrical arrangement of photovoltaic modules, the position of the photovoltaic modules on the vessel, the vessel’s tilting motion on the surface of the sea and the resultant irradiance based on the position of the Sun in the sky. Our approach allows the user to define these factors using a simple and intuitive graphical user interface so that a range of scenarios can be quickly simulated. We have used a basic test strategy that allows us to measure the effectiveness of different arrays and quantify performance in terms of mean output power and power stability over a range of sea conditions. A key factor in the effectiveness of the use of marine survey vessels is their ability to remain at sea for extended periods, preferably avoiding the use of high-carbon fuel sources such as diesel generators. This is of particular importance when observing marine life as the platform needs to operate as quietly as possible. The ASV Global C-Enduro autonomous, self-righting platform is the initial application for this new energy harvesting system, with the aim to extend mission endurance. A second case study has also been performed in parallel with this, using a much more divergent orientation of onboard photovoltaic modules in order to asses the ability for a dynamic photovoltaic array to increase and stabilise power output.