Momentum Transfer in Triboelectric Nanogenerators

The triboelectric nanogenerator (TENG) reflects a prospering field, that uses Maxwell's displacement current as the driving force to transform mechanical energy into electricity. Based on the law of energy conservation, many theoretical models of TENGs are proposed to provide a detailed insight into how energy flows and transformation in the energy harvesting system, while ignoring a hidden but extremely important point about TENG's momentum transfer and conservation. Here a series of analysis is presented for the momentum transfer and conservation in TENGs based on Maxwell equations and stress tensor. Using a time-dependent 3D mathematical model, it is elaborated that how the time- and spatial-dependent momentum current is influenced by the field and the dielectric materials, demonstrating that momentum is overall conserved for a TENG. In other words, the TENG device can not only convert mechanical energy into electricity, but it is also able to transfer momentum. Momentum transfer is another important characteristic of TENGs, and finally, the essential differences and similarities among the momentum transfer, energy transfer, and energy transformation in TENGs are systematically discussed. This study will certainly serve as a new starting point for exploring momentum transfer and conservation in the TENG momentum transfer system. This work, for the first time, proposes that triboelectric nanogenerators (TENGs) can not only convert mechanical energy into electrical energy, but also transfer momentum. Based on the main conclusions learned from this work, it is foreseen that the TENGs can expand their application range in physics science and engineering techniques, covering electromagnetic phenomena in detail, not just the interactions among model variables. image