Placeholder image for staff profiles

Ishara Dharmasena

My research project


Research interests

My teaching

My publications


Dharmasena R.D.I.G., Jayawardena K.D.G.I., Mills C.A., Deane J.H.B., Anguita J.V., Dorey R.A., Silva S.R.P. (2017). Triboelectric nanogenerators: providing a fundamental framework, Energy & Environmental Science 10 (8) pp. 1801-1811 Royal Society of Chemistry
View abstract View full publication
A new model which comprehensively explains the working principles of contact-mode triboelectric nanogenerators (TENGs) based on Maxwell's equations is presented. Unlike previous models which are restricted to known simple geometries and derived using the parallel plate capacitor model, this model is generic and can be modified to a wide range of geometries and surface topographies. We introduce the concept of a distance-dependent electric field, a factor not taken into account in previous models, to calculate the current, voltage, charge, and power output under different experimental conditions. The versatility of the model is demonstrated for non-planar geometry consisting of a convex–concave surface. The theoretical results show excellent agreement with experimental TENGs. Our model provides a complete understanding of the working principles of TENGs, and accurately predicts the output trends, which enables the design of more efficient TENG structures.
Dharmasena R.D.I.G., Jayawardena K.D.G.I., Mills C.A., Dorey R.A., Silva S.R.P. (2018). A unified theoretical model for Triboelectric Nanogenerators, Nano Energy 48 pp. 391-400 Elsevier
View abstract View full publication
A unified theoretical model applicable to different types of Triboelectric Nanogenerators (TENGs) is presented based on Maxwell’s equations, which fully explains the working principles of a majority of TENG types. This new model utilizes the distance-dependent electric field (DDEF) concept to derive a universal theoretical platform for all vertical charge polarization TENG types which overcomes the inaccuracies of the classical theoretical models as well as the limitations of the existing electric field-based model. The theoretical results show excellent agreement with experimental TENGs for all working modes, providing an improved capability of predicting the influence of different device parameters on the output behaviour. Finally, the output performances of different TENG types are compared. This work, for the first time, presents a unified framework of analytical equations for different TENG working modes, leading to an in-depth understanding of their working principles, which in turn enables more precise design and construction of efficient energy harvesters.
Dharmasena R.D.I.G., Deane J.H.B., Silva S.R.P. (2018). Nature of Power Generation and Output Optimization Criteria for Triboelectric Nanogenerators, Advanced Energy Materials DOI: 10.1002/aenm.201802190, WILEY-V C H VERLAG GMBH
View abstract View full publication
Triboelectric nanogenerators (TENGs) are in the forefront of next‐generation energy harvesting technologies, having been demonstrated as a leading candidate for numerous applications in energy harvesting and self‐powered sensing. However, critical parameters affecting TENG output behavior and their optimization are not well understood. Herein, for the first time, the power output characteristics of TENGs are fully unveiled by vigorously analyzing their impedance behavior as a function of excitation source and device parameters. In this paper, Norton's theorem, first presented in 1926 for two terminal linear electrical networks, is extended to represent TENGs, allowing accurate visualization of their dynamic power output behavior via small signal analysis. TENG impedance plots are introduced to accurately determine the peak power point of a given design, which holds paramount importance in understanding and improving TENGs. The knowledge with empirical understanding for these variations results in the design and construction of more efficient TENG devices for future applications.