Study of Contact Electrification at Liquid-Gas Interface

Abstract

It is known that the suspended liquid droplets in clouds can generate electrostatic charges, which finally results in the lightning. However, the detailed mechanism related to the contact-electrification process on the liquid-gas (L-G) interfaces is still poorly understood. Here, by introducing an acoustic levitation method for levitating a liquid droplet, we have studied the electrification mechanism at the L-G interface. The tribo-motion between water droplets and air induced by the ultrasound wave leads to the generation of positive charges on the surface of the droplets, and the charge amount of water droplets (20 μL) gradually reaches saturation within 30 s. The mixed solid particles in droplets can increase the amount of transferred charge, whereas the increase of ion concentration in the droplet can suppress the charge generation. This charge transfer phenomenon at L-G interfaces and the related analysis can be a guidance for the study in many fields, including anti-static, harvesting rainy energy, micro/nano fluidics, triboelectric power generator, surface engineering, and so on. Moreover, the surface charge generation due to L-G electrification is an inevitable effect during ultrasonic levitation, and thus, this study can also work for the applications of the ultrasonic technique.

Liquid‐Interfaces‐Based Triboelectric Nanogenerator: An Emerging Power Generation Method from Liquid‐Energy Nexus

“…Reproduced with permission. [29] Copyright 2021, American Chemical Society. liquids, such as organic solvents, inorganic solvents, ionic solutions, etc., corresponding to different solid surfaces, still requires further studies.…”

“…Usually, a higher droplet height results in the full triboelectrification between liquid and air, and the density of the surface charge of the droplet increases until saturation. [29,63] Additionally, as the height increases, the droplet speed and impact force increase. [60,68] As shown in Figure 10b-iii,c-iii, there is an increasing tendency of LI-TENG's output as the height of the droplet increases.…”

“…In Figure 2d, CE in liquid–gas interface is demonstrated. [ 29 ] A suspension device is used to control the contact process between liquid droplets and gas. It is found that when a droplet contacts with air, it becomes positively charged, and the charge on the droplet gradually reaches saturation when the suspension time exceeds 30 s. The transferred charge between the gas and liquid interface is affected not only by the gas but also the liquid.…”

“…d) The research about electrification between liquid and gas, which is achieved by an acoustic levitation system. Reproduced with permission [29]. Copyright 2021, American Chemical Society.…”

Crystallization-Induced Shift in a Triboelectric Series and Even Polarity Reversal for Elastic Triboelectric Materials

“…Most stretchable TENGs utilize polymer materials, such as all kinds of elastomers. − Meanwhile, many studies have revealed that the characteristics and the density of functional groups in a polymer can determine the electron transfer process during contact electrification. − For the commonly used stretchable triboelectric materials, the applied strain can induce many changes in the electrification process, while the underlying mechanism remains ambiguous. Usually, a change in the effective contact area , and the induced intermolecular forces , is considered to be the major effect changing the electrification performance.…”