Advanced Scalable Deposition of Polydimethylsiloxane for Both High and Low Energy Generation Applications

Abstract

Renewable energy generation has cemented itself as the main pillar in supplementing our future energy needs and subverting any crises in the next two to three decades. A complete shift towards sustainable generation has become the goal for most first-world nations, with much focus and resources being allocated for green energy research, infrastructure accommodations and sustainable energy generator implementation. From solar to wind, geothermal and mechanical energy, many research endeavors have been made to develop materials and processes capable of efficiently transforming these renewable resources into electricity, with a major focus placed mostly on large-scale production. However, sustainable material processing and smaller scale energy production are essential if the targets set are to be achieved, and research has been increasingly shifting towards it in the last decade. Small scale energy production through devices such as triboelectric nanogenerators have shown promise in the last decade, though they are still a long way from being appropriate mixtures to complement the impressive milestones reached so far at a bigger scale, as mostly complex engineered mixtures with complicated designs, high-cost materials and intricate processes have been crucial towards progress. Such an approach has come at great costs and incompatibility with current industrial processes and infrastructure. Hence, there is still a need for cost-effective and reliable material and process design. Throughout this thesis, the proposed work shows an alternative process called capillary climb film formation (CCFF) for thin film PDMS production, a material ubiquitous with renewable energy production among many other applications in fields such as medicine and microfluidics. The capabilities of this technique are thoroughly explored to better understand its limitations and highlight the advantages that it presents compared to other more traditional means of thin film production. Using CCFF, it is possible to form a large thin film from a small volume of PDMS mixture, while controlling its surface morphology on both sides pre-curing, combining the process of film formation and structuring into a simple single step. The technique also showed compatibility with vertical and horizontal capillary climb, which opens the door for single-step multi-film production. In addition to great control of the film’s structure, properties such as film thickness, material transparency, hydrophobicity and intricate internal designs can also be manipulated to obtain the desired results. Furthermore, the versatility of CCFF was demonstrated in its breadth of applicability, as the technique was employed to produce capacitive sensors, repair damaged films through the formation of a larger connected single film from torn pieces, as well as successfully encapsulate perovskite solar cells and improve their stability immensely, transforming them into devices that last over 60 days at peak performance in harsh conditions as opposed to ones that lose all their performance in less than 10 days. In terms of power generation, CCFF was used to obtain a PDMS thin film that would act as a tribonegative layer opposite the repurposed tribopositive monofilament fabric in a contact-separation model of a triboelectric nanogenerator (TENG). The maximum power output with the traditional device build was 12.16 mW/m2 achieved at a load of 20 MΩ, with an open-circuit voltage of 16.63 V. The device was even able to charge a 1 µF capacitor to 1.4 V in less than a minute. However, leveraging the versatility of CCFF to build the TENG itself presents a unique opportunity to leverage the advantages of this technique by building the device in a single step, foregoing the need for artificial separators, and maximizing the contact between both tribolayers through PDMS mixture climb in all three x, y and z directions. The final outcome was a device capable of producing 25.17 mW/m2 at 10 MΩ, while powering the 1µF capacitor to nearly 2.5 V in less than thirty seconds, showing the ability of a CCFF-built TENG to provide electricity to low power devices, while streamlining the building process and simplifying it.