Direct Observation of Single Particle Electrostatic Charging by Atomic Force Microscopy

Abstract

Using a combination of the abilities of AFM to scan in contact mode and record force-distance curves, we have shown a novel method to study electrostatic charging of particles. By measuring the length of the long range electrostatic interaction, we are able to compare different mechanisms of generating charge and to study the effect of RH on charge dissipation.

Decoupling the Eeffects of Esurface Chemistry and Humidity on Solid-State Hydrolysis of Aspirin in the Presence of Dicalcium Phosphate Dihydrate

“…30 Of the reports in the literature which refer to the observation of electrostatic interactions between pharmaceutical materials using AFM, tribocharging, caused by repeated contact between a particle and a substrate is the most common explanation. [30][31][32] However, in the results presented here, the long-range interaction was only observed on the (100) surface and only at high RH, observations which make tribocharging a less likely explanation. The presence of a water layer, for example, would be expected to quickly dissipate any charge effect which might result from such tribocharging.…”

Friction coefficient dependence on electrostatic tribocharging

“…Following tip detachment from the surface, its interaction with PTFE is also negligible. On the other hand, when PTFE is tribocharged, tip attraction during tip approach (but not during retraction) is observed at distances in excess of 500 nm5455. Moreover, tip-surface adhesion is largely increased.…”

Lactose characteristics and the generation of the aerosol

“…The electrical-single particle aerodynamic relaxation time analyser based on the laser Doppler velocimeter technique could also be used to assess electrostatic distribution and particle size on a single-particle basis [130,131], and the direct observation of single particle electrostatic charging by AFM has also been reported [132].…”