This Small Business Innovation Research (SBIR) Phase I project aims to develop a reinforced composite material that combines the antimicrobial effectiveness of nanoscale silver with the strength and weight of reinforced composites to meet the antifouling performance specifications of the marine environment. In this project, Carbon Nanotube (CNT)-infused glass fiber composites will be used. CNT-infused glass fiber composites not only provide an excellent solution to the weight and strength requirements, but also provide an ideal support for nanoscale silver integration due to the strong van der Waals interaction between the nanosilver particles and CNT systems. Additionally, the conductive nature of the CNT-infused composites coupled with the readily available source of electric current offer a perfect opportunity to utilize electrochemical silver ion release to create a tunable antifouling effect. This project is expected to verify that effective antifouling capabilities can be inherently integrated into the composites used in products such as tidal turbines, thereby extending their life and lowering operating costs.
The broader/commercial impact of this project will be the potential to provide an anti-fouling reinforced composite material for ocean renewable energy and marine applications. Ocean renewable energy is emerging as a key element of the alternative energy solution. One of the general challenges is to produce key components of the system which are strong, lightweight and durable, but also antifouling. The availability of cost-effective antifouling solution is essential for the wide adoption of ocean renewable energy.
The development of renewable sources of energy is proving to be a pivotal issue in meeting future energy requirements that would allow us to achieve environmentally sustainable economic growth. Of the current viable options, ocean renewable energy is emerging as one of the key elements of the alternative energy solution set. One of the general challenges in this field is the ability to produce key components of the system which are strong, lightweight and durable, but also antifouling. Fouling is a major issue for marine composite materials as it limits the service life and efficiency of ocean energy generation systems. This project focused on integrating a novel nanoscale silver based antifouling additive into a reinforced resin composite material used in products such as tidal turbines with the intention of extending their life and lowering operating costs. The objectives for Phase I of this project were to integrate a nanoscale silver based antimicrobial additive into carbon nanotube (CNT)-infused glass fiber resin composite materials at various loading levels and to characterize the effectiveness of these composites to resist colonization by both microfouling and macrofouling marine organisms. In addition to assessing the inherent antifouling characteristics of these composites, a low voltage DC potential applied to the composite for a brief period of time was evaluated as a potential means of electrochemically enhancing the composites ability to resist biofouling. We discovered through in vitro testing that a minimum nanoscale silver loading level of 0.50% silver by weight within the composite was necessary in order to successfully prevent bacteria associated with the microfouling of marine surfaces from colonizing the surface of the composites. It was also found that the rate at which silver ions, the active antimicrobial agent released from silver-based antimicrobial additives, are released from the surface of the silver treated composites can be enhanced by applying a low voltage DC bias to the composite materials. Subsequent in situ testing of the composite materials in a real marine environment revealed that the nanosilver treated composites significantly inhibited the rate at which biofouling occurred. Additional in situ testing also demonstrated that a single application of a low voltage DC electrical potential applied to the composites considerably improved the ability of the silver treated composite materials surface to resist colonization from marine biofouling organisms, especially hard fouling organisms. The results of this work have a much broader impact extending well beyond just improving the operating life and efficiencies of tidal turbines. While some cuprous oxide and organic based antifouling agents have proven effective at inhibiting fouling from occurring on various surfaces exposed to a marine environment for a period of time, they have also been shown to have significant deleterious effects on non-target marine organisms due to their inability to control the rate at which those agents are released into the environment. As such considerable efforts have been made recently to identify viable alternatives to these antifouling agents. Not only has the research conducted during Phase I of this project helped to establish a body of knowledge on how a nanoscale silver-based antimicrobial additive can be employed as a means of reducing marine biofouling on the surface of composites and coatings used in marine applications but it has also yielded strong empirical proof that such an approach is indeed feasible. This research has also demonstrated that unlike current self-polishing antifouling agents, the antifouling properties of these nanoscale silver treated marine composites can potentially be tuned to produce surfaces that are highly resistant to biofouling without inadvertently damaging marine ecosystems. It is for this reason that this technology could provide both an ecologically safer and more economically attractive alternative to current antifouling technologies used in marine applications.