Triboelectric Charging of Particles, an Ongoing Matter: From the Early Onset of Planet Formation to Assembling Crystals

Abstract

Triboelectrification is the spontaneous charging of two bodies when released from contact. Even though its manifestation is commonplace, in for instance triboelectric nanogenerators, scientists find the tribocharging mechanism a mystery. The primary aim of this mini-review is to provide an overview of different tribocharging concepts that have been applied to study and realize the formation of ordered stable structures using different objects on various length scales. Relevance spans from materials to planet formations. Especially, dry assembly methods of particles of different shapes based on tribocharging to obtain crystal structures or monolayers are considered. In addition, the current technology employed to examine tribocharging in (semi)dry environments is discussed as well as the relevant forces playing a role in the assembly process. In brief, this mini-review is expected to provide a better understanding of tribocharging in assembling objects on the nano-and micrometer scales.

Influence of Wettability and Geometry on Contact Electrification between Nonionic Insulators

“…Although the empirically established triboelectric series can potentially explain the direction of charge transfer, often deviations are observed, , the series fails to explain the dependence on the humidity observed in Figure . Note that the relative positions of materials in the triboelectric ladder do not reflect the total amount of charge that can be exchanged at any humidity level . The electrostatic interaction is enhanced with increasing RH for a hydrophilic silica colloid interacting with a hydrophobic CF x layer.…”

“…However, the exact mechanism at the heart of this phenomenon is still under debate. For insulators, even the nature of the charge carrier associated with contact charging has not been settled. , Basically, three kinds of charge transfer mechanisms are proposed: (i) electron transfer, (ii) ion transfer, and (iii) transfer of material . The reason that a unifying mechanism explaining the tribocharging is missing can be ascribed to the fact that the electrostatic interactions between surfaces are highly complex as they hinge on material, , size, electrical properties, surface properties, and relative humidity (RH) as well. , …”

“…4,48 Basically, three kinds of charge transfer mechanisms are proposed: (i) electron transfer, (ii) ion transfer, 1 and (iii) transfer of material. 2 The reason that a unifying mechanism explaining the tribocharging is missing can be ascribed to the fact that the electrostatic interactions between surfaces are highly complex as they hinge on material, 3,4 size, 5 electrical properties, surface properties, 6 and relative humidity (RH) as well. 7,8 Understanding the contact electrification mechanism at the micro-and nanoscale is pivotal, as it is currently leveraged in many energy applications, e.g., in triboelectric nanogenerators (TENGs), introduced by the Wang group in 2012, 9,10 which received great attention as a new energy harvesting application, such as mechanical energy harvesting, self-powered sensing, and tribotronics.…”

Prediction of the Effective Work Function of Aspirin and Paracetamol Crystals by Density Functional Theory─A First-Principles Study

“…The work shown here provides a basis on which an understanding of charge transfer between different pharmaceutical crystals can be built. Second, it provides insight into the poorly understood phenomenon of the triboelectrification of chemically identical materials . Based on this work and the papers previously discussed, ,, it is very unlikely that the surface effective WF profile of any particulate solid is homogeneous, implying that triboelectric charge transfer can readily occur for the same material.…”

Impact-induced generation of single airborne microspheres and the subsequent vacuum-driven assembly of ordered arrays

“…Not all collisions are likely pure elastic collisions, and some particles may also undergo inelastic collisions where the colliding particles stick together. Furthermore, the contact electrification mechanism could induce an electrostatic attraction between single colliding particles [19,[34][35][36]. It is plausible that all three mechanisms contribute to the re-agglomeration process of single powder microspheres.…”