The Charging Events in Contact-Separation Electrification

Abstract

Contact electrification (CE)—charging of surfaces that are contacted and separated, is a common phenomenon, however it is not completely understood yet. Recent studies using surface imaging techniques and chemical analysis revealed a ‘spatial’ bipolar distribution of charges at the nano dimension, which made a paradigm shift in the field. However, such analyses can only provide information about the charges that remained on the surface after the separation, providing limited information about the actual course of the CE event. Tapping common polymers and metal surfaces to each other and detecting the electrical potential produced on these surfaces ‘in-situ’ in individual events of contact and separation, we show that, charges are generated and transferred between the surfaces in both events; the measured potential is bipolar in contact and unipolar in separation. We show, the ‘contact-charges’ on the surfaces are indeed the net charges that results after the separation process, and a large contribution to tribocharge harvesting comes, in fact, from the electrostatic induction resulting from the generated CE charges. Our results refine the mechanism of CE providing information for rethinking the conventional ranking of materials’ charging abilities, charge harvesting, and charge prevention.

Natural and Eco-Friendly Materials for Triboelectric Energy Harvesting

“…During the motion process (sliding or separation), opposite charges on the surface of materials are produced, whose amount will significantly increase if the surface area increases and changes according to the different composition and structure of materials [24,25]. Several studies have been conducted to understand the charge formation mechanisms, and they also provided the basis for measurements standards [26][27][28]. In another work, Zou et al [29] demonstrated how to measure triboelectricity by using several polymers as examples.…”

Tribo-Charging Behaviour of Inhalable Mannitol Blends with Salbutamol Sulphate

“…The concept of “effective work function” has been proposed and relates the transfer of species from high-energy states to a low energy surface during contact charging of insulators ( 10 ). Unlike metals, tribo-charging of insulators involves not only the exchange of electrons, but also of ions and material ( 11 , 12 ). The relative contribution of each mechanism depends upon the mode of contact and stresses generated within the materials.…”

“…The relative contribution of each mechanism depends upon the mode of contact and stresses generated within the materials. The resulting net charge is a consequence of the balance between the contribution of the negative and positive species ( 11 , 12 ). After contact, the acquired charge will dissipate (decay) at a rate specific to the material and environment ( 12 ).…”

Toward High‐Performance Triboelectric Nanogenerators by Engineering Interfaces at the Nanoscale: Looking into the Future Research Roadmap

“…However, unidirectional electron transfer that is justified by charge formation through bond breaking helps in understanding the underlying mechanism. [ 44,58–60 ]…”