Simultaneous measurement of triboelectrification and triboluminescence of crystalline materials

Abstract

Triboelectrification has been studied for over 2500 years, yet there is still a lack of fundamental understanding as to its origin. Given its utility in areas such as xerography, powder spray painting, and energy harvesting, many devices have been made to investigate triboelectrification at many length-scales, though few seek to additionally make use of triboluminescence: the emission of electromagnetic radiation immediately following a charge separation event. As devices for measuring triboelectrification became smaller and smaller, now measuring down to the atomic scale with atomic force microscope based designs, an appreciation for the collective and multi-scale nature of triboelectrification has perhaps abated. Consider that the energy required to move a unit charge is very large compared to a van der Waals interaction, yet peeling Scotch tape (whose adhesion is derived from van der Waals forces) can provide strong enough energy-focusing to generate X-ray emission. This paper presents a device to press approximately cm-sized materials together in a vacuum, with in situ alignment. Residual surface charge, force, and position and X-ray, visible light, and RF emission are measured for single crystal samples. Charge is therefore tracked throughout the charging and discharging processes, resulting in a more complete picture of triboelectrification, with controllable and measurable environmental influence. Macroscale charging is directly measured, whilst triboluminescence, originating in atomic-scale processes, probes the microscale. The apparatus was built with the goal of obtaining an ab initio-level explanation of triboelectrification for well-defined materials, at the micro- and macro-scale, which has eluded scientists for millennia.

Mechanoluminescence of Ce/Tb inorganic salts in methane–acetylene mixtures with inert gases

“…Processes of charging and strong local electric fields play a decisive role in the luminescence upon mechanodestruction . Therefore, they significantly influence the gas component of the ML spectrum, which almost coincides with the discharge spectra in the gas atmosphere .…”

Nanoscale Modulation of Friction and Triboelectrification via Surface Nanotexturing

“…Further improving the nanoscale elastomeric CE requires understanding of its physical mechanism. In general, CE is attributed to the interfacial friction during the separation and the resulting generation of triboelectric charge. − However, the detailed process relating the two on elastomeric nanotextures is still elusive, despite significant advances in Kelvin probe force microscopy (KPFM) − and nanoscale charge characterization techniques based on it. ,− …”

Quantum Theory of Triboelectricity

“…Considering bosonic superradiance in terms of open quantum systems clarifies the respective roles of macroscopic motion, dissipation, and stimulated emission [10]. Here we have extended that analysis to fermions, allowing us to propose a microphysical explanation of the persistent conversion of macroscopic motion into an emf, something that cannot be obtained from density functional theory or other equilibrium descriptions [28].…”

“…If the distance goes from interatomic to 10 µm scale, the energy of the electrons can be in the visible range ( 1 eV). On triboluminescence, see [28] and references therein.…”