Vol. 54 No. 4 2021 135 Copyright © 2021 The Society of Chemical Engineers, Japan Journal of Chemical Engineering of Japan, Vol. 54, No. 4, pp. 135–143, 2021 Detachment of Submicron Particles from Substrates Using the Suspension-Assisted Ultrasonic Method M. P. Khairunnisa 1,2 , Ferry Faizal 1,3 , Eiji Miyazawa 4 , Kohji Masuda 1,5 , Mayumi Tsukada 4 and I. Wuled Lenggoro 1,4 1 Graduate School of Bio-Applications and Systems Engineering, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei-shi, Tokyo 184-8588, Japan 2 Department of Chemical and Environmental Engineering, Malaysia-Japan International Institute of Technology, Universiti Teknologi Malaysia, Jalan Sultan Yahya Petra, 54100 Kuala Lumpur, Malaysia 3 Department of Physics and Functional Nano Powder University Research Centre of Excellence, Universitas Padjadjaran, Jl. Raya Bandung-Sumedang Km. 21, Sumedang 45363, Indonesia 4 Department of Chemical Engineering, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588, Japan 5 Department of Electrical and Electronic Engineering, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho, Koganei-shi, Tokyo 184-8588, Japan Keywords: Aerosol Collection, Particle Detachment, Bubble Dynamics, Surface Morphology 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, respec- tively. 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 par- ticle size distribution after ultrasonication showed good dispersion of the sample particles in the soot suspension. Introduction Ultrasound is widely employed in chemical and industrial processes because its energy is very intense and less harmful than that of other methods. Sonochemistry with ultrasound was first reported in the early nineteenth century (Rich- ards and Loomis, 1927). Since then, interest in ultrasound has been growing for applications such as emulsification (Yasuda et al., 2012), particle processing (Horie et al., 2014), particle fractionating (Suzuki et al., 2012), and the clean- ing of solids, which has made a remarkable contribution to the semiconductor industry as a procedure for removing particles in the micron or submicron range from product surfaces (Kashkoush and Busnaina, 1993). Most of the process improvements using ultrasound have been achieved using cavitation bubbles induced by ultrason- ic waves traveling through a liquid medium. ese bubbles have dynamic behaviors such as oscillation, growth, transla- tion, and collapse (Brennen, 1995). Bubble collapse, which is enhanced by the heterogeneity of the near-wall field around a body, plays an especially important role in removing par- ticles from a solid body immersed in an ultrasonic medium. In addition, it is occasionally accompanied by a turbulent jet and shock waves. e performance of ultrasonic cleaning is oſten characterized by cavitation behavior (Gale and Busnai- na, 1999; Niemczewski, 2007). Water containing chemicals or solvents has been applied as cleaning media to enhance the cleaning performance of silicon wafers for semiconduc- tors (Menon et al., 1989) and filters (Choi et al., 2016). e application field is expected to be extended by the introduc- tion of a solid–liquid suspension to the cleaning medium, as schematically shown in Figure 1. e expansion and com- pression of cavitation bubbles may work to push particles of the cleaning medium to collide with the particles adhered to the substrate, thus removing them from the substrate. If the particle media conditions are chosen properly, the particles will not adhere to the substrate. When a high degree of cleanliness is required, particles in suspension are not welcome; this is especially true concern- ing the prevention of damage to the substrate during semi- Received on October 28, 2016; accepted on October 11, 2017 DOI: 10.1252/jcej.16we319 Correspondence concerning this article should be addressed to I. W. Lenggoro (E-mail address: wuled.@cc.tuat.ac.jp). ORCiD ID of I. W. Lenggoro is https://orcid.org/0000-0002-0048-8486 Research Paper