# Micro-Nanobubble Technology in Surface Cleaning and Defouling
## 4 Biofouling Mitigation and Advanced Cleaning Technologies
### Technological Innovations  
Novel approaches for surface cleaning and biofilm defouling have been made possible by recent developments in NB and related technologies that have addressed issues in industrial, environmental, and medical applications [5; 6]. These technologies use physical forces, reactive species production, and innovative delivery systems to increase cleaning effectiveness and reduce surface damage [8].  
[PERSON] et al. [81] presented a new cleaning tool that improves biofilm removal from foul release coatings (FRCs) using an ultrasonically activated stream (UAS). The UAS was tested on two types of commercial FRCs submerged in a marine environment for 12 days to increase the efficacy of MBs in a flowing water stream using ultrasound. The findings demonstrated that, in comparison with conventional water cleaning, the UAS greatly enhanced biofilm removal, almost completely removing detectable biofilms from surfaces and resulting in significant decreases in surface coverage and biovolume. Following the UAS cleaning, the surface roughness of the coatings remained comparable to that of the unexposed coatings, suggesting that no damage occurred. All things considered, the UAS was shown to be a successful and non-harmful technique for eliminating biofilms from antifouling coatings.  
[PERSON] et al. [108] discussed the use of vapor NBs (VNBs), which are made from laser-irradiated nanoparticles, to break up bacterial biofilms and improve the manner in which light-responsive nanocarriers release antibiotics (Figure 16). _Pseudomonas aeruginosa_ biofilms were tested using tobramycin in two different nanocarriers: graphene quantum dots (GQDs) and liposomes functionalized with gold nanoparticles (AuNPs). Although the antibiotic's anti-biofilm effectiveness was enhanced by liposomal encapsulation, the advantages of laser irradiation and VNB formation were undermined by the early drug leakage caused by the AuNPs. However, because of ineffective drug release, tobramycin adsorbed onto GQDs did not produce an improved anti-biofilm effect despite achieving stable formulations. The study emphasized the difficulties in creating efficient nanocarriers for the simultaneous disruption of biofilms and light-triggered release of antibiotics, highlighting the need to strike a balance between stability and drug release for the best possible treatment results.  
For applications in water purification, specifically for pathogen inactivation and biofilm removal, the interactions between cold atmospheric pressure plasmas and water have been extensively investigated. [PERSON] et al. [85] proved that while preserving whole  
Figure 16: Biofilm diffusion barrier and the potential of laser-induced vapor NBs (VNBs) to improve antibiotic delivery to biofilms. Reproduced with permission from [108], CC-BY license, Copyright © 2019, the authors. Licensee MDPI, Basel, Switzerland.  
some aquatic conditions, underwater microplasma bubbles produced by a microplasma-bubble reactor can efficiently transfer reactive plasma species to surfaces covered in a biofilm. With the use of microplasma bubbles and plasma-activated water (PAW), the treatments reduced the pathogenic biofilm load by approximately 83% and 60%, respectively, and stopped the formation of new biofilms. Brief daily exposure to microplasma bubbles in a custom fish tank led to an 80-90% decrease in biofilm-infected areas and an improvement in fish health. Ozone, nitrite, nitrate, hydrogen peroxide, and nitric oxide were among the most important reactive species produced, and nitric oxide was crucial for the dispersal and inactivation of the biofilms. Overall, the results showed that RONS in PAW can effectively control biofilms, offering insights into plasma-liquid interactions and opening the door for real-world water treatment applications.