Micro-Nano Bubbles: A New Field of Eco-Friendly Cleaning

Abstract

Due to increasing public awareness of environmental concerns and stricter cleaning process requirements, traditional cleaning technologies characterized by high pollution, excessive energy consumption, and substantial damage are insufficient to meet contemporary demands. There is an urgent need for efficient, low-damage, and environmentally friendly cleaning technologies. In recent years, the rapid advancement of micro-nano bubbles (MNBs), which exhibit unique physicochemical properties, have emerged as a promising solution for green cleaning applications. This review begins with an overview of the benefits of MNBs in cleaning processes, followed by an in-depth analysis of the factors influencing their cleaning effectiveness as well as the possible mechanisms involved. Additionally, the producing and application of MNBs across various cleaning scenarios are summarized. Finally, prospects for their development are discussed. Research and advancements in MNB preparation technologies are expected to boost their applicability and commercialization in a greater variety of cleaning contexts in the future.

Keywords: contaminant removal; eco-friendly technique; micro-nano bubbles; surface cleaning.

Figure 1

An overview of the properties, mechanisms, and applications of MNBs along the cleaning process.

Figure 2

Physical mechanisms of MNBs: (a) altering the adhesions, (b) departing from surface with contaminations, and (c) reducing absorption.

Figure 3

Chemical mechanisms of MNBs: (a) reactive ROS and (b) ionic interactions.

Figure 4

O₃-NBs remove photoresist [20]. High-dose ion implantation photoresist is shown to be removed from the outer edges of the wafer to the interior at 0, 5, and 10 min after the start of processing. Reprinted with permission from Ref. [20]. Copyright 2012, copyright American Chemical Society.

Figure 5

Stainless-steel test pieces after cleaning with (a,c) or without (b,d) MNBs [79]. Reprinted with permission from Ref. [79]. Copyright 2022, copyright American Chemical Society.

Figure 6

Diatom nanosheets doped with MnO₂ produce O₂-MBs that destroy the biofilm. A number of bacteria are killed after H₂O₂ molecules diffuse into the biofilm [77]. Reprinted with permission from Ref. [77]. Copyright 2018, copyright American Chemical Society.

Figure 7

MNBs are used to clean porcelain artifacts [128,129]. Impurities are reduced and cracked surfaces are not deepened after cleaning. Adapted with permission from Refs. [128,129]. Copyright 2017 and 2020, copyright Sciences of Conservation and Archaeology.