Detachment of submicron particles from substrates using the suspension-assisted ultrasonic method

Abstract

A protocol for the detachment of solid samples deposited on flat substrates and their collection in aqueous samples is proposed based on a suspension-assisted ultrasonic method. As samples, combustion-synthesized magnesium oxide aggregates in the submicron size range were deposited in the gas phase onto three kinds of substrates: a silicon wafer and coarse and fine alumina-coated resin sheets. To enhance the sample particle detachment, a solid–liquid suspension made of candle combustion soot particles was selected as an ultrasound propagation medium, which is different from the usual liquid medium, such as water, a surfactant solution, or a solvent. Preliminary detachment experiments were performed using low-power (42 kHz and 35 W) ultrasonication, and the substrates and suspensions were analyzed using scanning electron microscopy (SEM) images and particle size distributions based on dynamic light scattering, respectively. The detachment efficiency, defined as the fraction of cleaned area on a substrate, was determined from the SEM images and indicates that the detachment using the medium with soot had a higher efficiency compared to that without soot, and there was an optimum soot concentration for particle detachment for all three substrates. The suspension particle size distribution after ultrasonication showed good dispersion of the sample particles in the soot suspension.