# Micro-Nanobubble Technology in Surface Cleaning and Defouling
## 1 Introduction  
Micro-nanobubbles (MNBs) encompass both nanobubbles (NBs), which are less than 1 \(\upmu\)m in diameter, and microbubbles (MBs), which range from 1 to 100 \(\upmu\)m [1, 2]. Their remarkable physicochemical properties and myriad uses have attracted significant attention in recent years [3, 4]. Unlike common bubbles, owing to their exceptional stability, high internal pressure, and negative surface charge, NBs can survive for a long time in liquid settings [5, 6, 7]. Due to their special properties, NBs are useful for solving important problems in various fields, including advanced cleaning technologies, healthcare, agriculture, and environmental remediation [8]. In contrast, MBs are larger and less stable than NBs, but they are essential for applications requiring faster surface interaction or improved gas transmission. Under some circumstances, MBs dissolve or contract to create NBs, which improves the efficiency of oxygen transfer in procedures like advanced oxidation and bioremediation [9]. The ability of NBs to clean and defoul surfaces is one of their most important applications. Their high surface area-to-volume ratio and capacity to produce reactive oxygen species (ROS) during cavitation events improve membrane cleaning, biofilm removal, and organic pollutant degradation [10]. For example, research has demonstrated that NBs offer an environmentally acceptable substitute for traditional cleaning techniques by considerably increasing the membrane permeability while reducing fouling [11]. This has been particularly helpful in water treatment facilities, where NBs lower operating costs and chemical reliance [12]. Significant progress has been made in the creation of NBs using cavitation, electrochemical processes, and gas dissolution, allowing for their incorporation into various cleaning systems [13]. The dynamics of NBs can be tailored to specific uses, such as fouling prevention and precision cleaning. Additionally, the stability and efficacy of NBs in interacting with pollutants and surfaces are enhanced by their high zeta potential. The size of MBs allows them to interact more dynamically with contaminants and surfaces, making them effective for removing suspended particles and preventing fouling in water treatment systems [6]. MBs and NBs, separately and together, i.e., MNbs, show significant potential when combined with bioremediation, advanced oxidation processes, and microbial management strategies [14]. These cooperative methods increase cleaning effectiveness in industrial settings by using the cavitation effects of NBs to dissolve biofilms and complicated organic compounds. The cavitation effects in NBs happen in dynamic conditions, even though NBs are naturally stable in typical situations. NBs are often quite stable because of their small size and gas content, but cavitation problems can be brought on by outside variables including variations in temperature, pressure, or fluid velocity [15]. For instance, the function of NBs in wastewater treatment has been emphasized [16]. Their capacity to facilitate oxygen transfer and create free radicals improves the breakdown of contaminants and reduces the development of excess sludge [17]. In addition to their positive effects on the environment, MBs and NBs have shown promise in high-precision cleaning applications [18; 19]. In industries such as medical device sterilization and semiconductor fabrication, customized solutions are made possible by the ability to regulate bubble size and concentration [20]. They are also appropriate for delicate cleaning duties because they have little effect on substrate surfaces, which lowers the possibility of surface damage [21]. Despite these benefits, the broad use of bubble technology faces several obstacles. Optimizing generation techniques, scaling up for commercial use, and comprehending the principles underlying their stability are important research subjects [22; 23]. Further research is required to understand how bubble behavior varies depending on temperature, pH, and salinity [16].