# Micro-Nanobubble Technology in Surface Cleaning and Defouling
## 3 Advanced Applications of NBs in Precision Surface Cleaning
### Eco-Friendly Surface Cleaning and Contamination Prevention  
An inventive tool for effective and sustainable surface cleaning, NBs provide environmentally friendly substitutes for conventional techniques. ROS are produced by them, which makes them very efficient at eliminating impurities, avoiding fouling, and preserving surface integrity [41]. The research discussed below demonstrates how NBs can improve surface cleaning while reducing the negative effects on the environment. [PERSON] et al. [60] quantitatively examined how well NBs worked for surface cleaning, and particularly, how well they removed nanosized polystyrene particles from plain or nanopatterned silicon wafers (Figure 8). NBs were produced using the alcohol-water exchange method, which involves washing an alcohol-covered surface with water. This technique produced high-density NBs, particularly on surfaces with nanopatterns. In contrast to traditional fluidic cleaning techniques, such as water rinsing, alcohol rinsing, and water-alcohol exchange, which result in little to no particle removal, the findingsdemonstrated that NBs effectively remove nanoparticles from both surface types. Surface examination with SEM, HIM, and AFM showed that tapping-mode AFM in liquid may see the removal of nanoparticles as well as the development of NBs. This study highlighted that nanopatterned surfaces with nanotrenches, which are generally difficult to clean using other techniques, respond particularly well to NB cleaning. The cleaning efficiency also increased by increasing the number of treatment cycles, and the NB cleaning procedure did not damage the nanoscale surface structures. [PERSON] et al. [61] investigated the application of NBs created by electrolyzing NaCl solutions to clean and prevent fouling on both hydrophilic and hydrophobic surfaces. The NBs, which had a diameter of approximately 90 nm, were present at a concentration of approximately 5 \(\times\) 10\({}^{8}\) per milliliter and remained stable for approximately 24 h. They were easily removed using a 20 nm filter and had a negative charge at neutral pH. According to these findings, NBs were less effective at cleaning hydrophobic surfaces than hydrophilic ones that had already become soiled. Additionally, they stopped fouling on both types of surfaces; however, this ability decreased as the contaminant's concentration or surface affinity increased. This study contended that the main function of cleaning agents such as NBs in mechanically agitated rapid cleaning applications is to suspend and stop the redeposition of soil that has been mechanically removed from surfaces rather than directly aiding the removal of contaminants. NBs' main function during cleaning procedures is likely to be this mechanism. [PERSON] et al. [62] demonstrated a novel electrochemical method for producing surfaces with both antibacterial and antifouling properties. Hydrogen gas bubbles were created by applying low-voltage square-waveform pulses to a favorable surface, creating a barrier that prevented bacteria from adhering. According to the results, this method killed preadhered _Escherichia coli_ (_E. coli_) through water stress, which was brought on by the dry environment produced by the hydrogen evolution process, and it reduced bacterial adhesion by 99.5%. According to the research, this technique can be used with photocatalytic and photoelectrochemical reactions to create self-sustaining antifouling solutions. [PERSON] et al. [63] compared the cleaning effects of vapor and gas bubbles in ultrasonic fields through experimentation. According to high-speed videography, gas bubbles cleaned by circulating about the surface for long periods, whereas vapor bubbles cleaned more quickly by exploding and producing dispersed cleaning events. According to these findings,  
Figure 8: SEM images of (**a**) the plain wafer surface deposited with the 100 nm polystyrene particles and (**b**) the same surface after it has been treated with the ethanol–water exchange process and dried again.