Triboelectric self-powered energy systems.

Next generation electronics are shaping the life of people by digitally connecting humans and everyday objects using smart technologies. A major challenge related to such technologies is powering the electronic devices while maintaining autonomy and mobility. Triboelectric Nanogenerators (TENGs) provide innovative solutions for powering next generation low-power electronics, by converting movement into electricity. However, these devices are still in their infancy with numerous drawbacks including high device impedance, low output power density and efficiency, mainly due to the lack of understanding of their working principles and optimization techniques. This thesis investigates the fundamental working principles of TENGs and some of their applications as energy harvesting devices. The electric field behaviour of different TENG architectures is studied using Maxwell’s equations, leading to the derivation of the distance-dependent electric field (DDEF) model. This new model is capable of fully explaining the electric field behaviour and working principle of TENGs, overcoming the drawbacks of previous models. The DDEF model is developed initially for the vertical contact-separation mode TENG and expanded to represent all working modes which utilise contact-separation movement, via the development of unified DDEF model. The models are then used to simulate the output trends of different experimental TENG devices. An experimental setup is developed and TENG devices fabricated to assess the DDEF model predictions, which verifies the higher accuracy of the new model over previous capacitor-based circuit models. Using the unified DDEF model as a framework, the effect of different structural and motion parameters of TENGs on their power output is studied. A number of new analysis techniques are introduced, including the TENG power transfer equation and TENG impedance plots, to identify the output trends and optimisation routes to design TENG devices, resulting an increase of power and reduction of TENG internal impedance by more than an order of magnitude. Finally, application of theoretical knowledge gained from the DDEF model is demonstrated by constructing a direct current output TENG device. This new design produces a constant power output subjected to continuous input motion, showing the potential to be used in self-powered electronic applications