Triboelectric nanogenerator (TENG) is a field that uses Maxwell’s displacement current as the driving force to covert the widely distributed and disorganized mechanical energy into electricity, which is capturing lots of researchers’ attention. The effects of contact electrification (CE) creating tribo-charges on the contacting surfaces of TENGs are the physics base for energy conversion. It is universally acknowledged that contact electrification involves a complex interplay of physical interactions in realistic material systems. For this reason, scientific consensus on the qualitative and quantitative importance of different physical mechanisms on CE remains a formidable task. Although an electron cloud model of CE has been proposed by Zhonglin Wang’s group and has a possible universal range of applicability, its accuracy and reliability need further validation. Since CE, a time-dependent polarization term Ps is added in electric displacement (D) in order to identify the contribution from the surface charges that are independent of the external electric field. Therefore, Maxwell’s equations are expanded to describe the process of polarization of electric medium under an external electric field (P) and non-electric field (Ps), which provides not only the possibility of proving the displacement current as the driving force of TENGs but also the theoretical basis of the TENG energy harvesting system.
Electromagnetic fields are generally functions of time and of space coordinates and are represented by their magnitude and, for vector fields additionally, direction. Although the laws of electromagnetism are the same in all coordinate systems, relationships among variables are conveniently expressed in a coordinate system reflecting the geometry. This is why a general theoretical model of the TENG allows a detailed understanding of the charge distribution, being beneficial for revealing the time variation electric field, polarization, and importantly the displacement current. Accordingly, mathematical models, equivalent electrical circuit models, and electromechanical coupling models have been present, which are effective and accurate methods to explore the output power, electromagnetic characteristics of a TENG energy harvesting system. On the other hand, TENGs have huge advantages and therefore can be applied in the field of self-powered sensors, power sources, blue energy harvesting, energy science, or as moving measurement probes for interfacial science.
This Research Topic of Frontiers in Materials aims not only to give a brief overview of the progress but also provide some comments on future challenges and opportunities. Areas to be covered in this Research Topic may include, but are not limited to:
• Scientific Mechanisms of Contact Electrification;
• Fundamental Laws of Physics: Expanded Maxwell’s Equations and Displacement Current;
• Physical Mechanisms of Triboelectric Nanogenerators;
• Modelling & Simulation of a dynamic physical system;
• Advanced Technologies of Triboelectric Nanogenerators.
Triboelectric nanogenerator (TENG) is a field that uses Maxwell’s displacement current as the driving force to covert the widely distributed and disorganized mechanical energy into electricity, which is capturing lots of researchers’ attention. The effects of contact electrification (CE) creating tribo-charges on the contacting surfaces of TENGs are the physics base for energy conversion. It is universally acknowledged that contact electrification involves a complex interplay of physical interactions in realistic material systems. For this reason, scientific consensus on the qualitative and quantitative importance of different physical mechanisms on CE remains a formidable task. Although an electron cloud model of CE has been proposed by Zhonglin Wang’s group and has a possible universal range of applicability, its accuracy and reliability need further validation. Since CE, a time-dependent polarization term Ps is added in electric displacement (D) in order to identify the contribution from the surface charges that are independent of the external electric field. Therefore, Maxwell’s equations are expanded to describe the process of polarization of electric medium under an external electric field (P) and non-electric field (Ps), which provides not only the possibility of proving the displacement current as the driving force of TENGs but also the theoretical basis of the TENG energy harvesting system.
Electromagnetic fields are generally functions of time and of space coordinates and are represented by their magnitude and, for vector fields additionally, direction. Although the laws of electromagnetism are the same in all coordinate systems, relationships among variables are conveniently expressed in a coordinate system reflecting the geometry. This is why a general theoretical model of the TENG allows a detailed understanding of the charge distribution, being beneficial for revealing the time variation electric field, polarization, and importantly the displacement current. Accordingly, mathematical models, equivalent electrical circuit models, and electromechanical coupling models have been present, which are effective and accurate methods to explore the output power, electromagnetic characteristics of a TENG energy harvesting system. On the other hand, TENGs have huge advantages and therefore can be applied in the field of self-powered sensors, power sources, blue energy harvesting, energy science, or as moving measurement probes for interfacial science.
This Research Topic of Frontiers in Materials aims not only to give a brief overview of the progress but also provide some comments on future challenges and opportunities. Areas to be covered in this Research Topic may include, but are not limited to:
• Scientific Mechanisms of Contact Electrification;
• Fundamental Laws of Physics: Expanded Maxwell’s Equations and Displacement Current;
• Physical Mechanisms of Triboelectric Nanogenerators;
• Modelling & Simulation of a dynamic physical system;
• Advanced Technologies of Triboelectric Nanogenerators.
