Biofouling is a common challenge for underwater sensors, especially for long-term in situ monitoring in marine environments. Biofouling on in situ sensor surfaces can shorten their operating lifetime, increase the cost and frequency of maintenance, and result in signal drift and data errors. Therefore, an effective method to control fouling is needed for applications that rely on in situ sensors in marine environments. 

Natural products with antifouling properties have been investigated as promising sources of environmentally friendly antifoulants. However, most studies only employ laboratory tests to evaluate the antifouling efficacy of natural products. 

Recently, a team consisting of researchers from the Shenzhen Institute of Advanced Technology (SIAT) of Chinese Academy of Sciences and Xiamen University, has studied to prove that camptothecin (CPT) exhibited effective antifouling activity and lower toxicity. Their latest study showed significantly lower macrofouling coverage on the areas painted with the CPT-based paint compared to the unpainted areas for 6 materials over 9 months of seawater immersion. 

The result was published in International Biodeterioration & Biodegradation on 18 March, 2022.  

The tested panels were made from six different materials, including three metals (316 L stainless steel, TC4 titanium alloy, and 7075 aluminum alloy) and three plastics (polyoxymethylene, polyvinyl chloride, and Teflon). These materials have been widely used for constructing underwater sensor housings. Then the panels were hung under a floating raft in Xiamen Bay, China since July 7, 2019 at a depth of 1 m in seawater for 9 months. 

After 9 months of submersion, the CPT-based paint exhibited good antifouling performance, reducing biofouling by 73.33%–96.41% compared to the control unpainted areas (100% coverage). In particular, the antifouling of plastic material is better than that of metal material. 

"Our results suggest that the CPT-based paint could be used as a potential solution to control the biofouling of sensor housings for long-term in situ applications in marine environments," said Prof. FENG Danqing, one of the corresponding authors of this study. 

In addition, the team had also deployed three underwater sensors under a moored surface buoy platform in Daya Bay, Shenzhen, China since June 22, 2020. After 4 months of deployment under a surface buoy in the marine environment, the sensors still remained clean. 

"It is worth noting that the CPT-based paint also has great potential for other artificial submerged structures in the marine environment, such as ship hulls, oil platforms and aquaculture facilities," said Prof. LI Jianping, who was the co-corresponding author of this paper.  

Test panels before and after immersion in seawater at different time points. (Image by SIAT) 

Biological adhesion on the surface of the Marine in situ sensor housing with a CPT-Based paint (right) versus untreated (left)  (Photo by SIAT)