UUVs are increasingly being used for a wide range of applications, from underwater exploration and surveillance to mine detection and mapping of the ocean floor. These vehicles are typically designed to operate autonomously, without human intervention, and can be deployed for extended periods of time.
However, UUVs can face significant challenges due to marine biofouling, which is the accumulation of microorganisms, plants, and animals on the surface of the vehicle. Marine biofouling is a natural process that occurs in all bodies of water, and can be particularly severe in warm, nutrient-rich environments.
The accumulation of marine biofouling on the surface of a UUV can cause a range of problems, including increased drag. As biofouling accumulates on the surface of the UUV, it can increase drag and reduce the vehicle’s speed and maneuverability. This can significantly impact the vehicle’s range and operational capabilities, and may require it to return to the surface for cleaning or maintenance.
Bacteria are the most abundant and diverse lifeform on Earth, coating almost every surface, with the majority spending their lives in biofilms. This lifestyle is universally perceived as problematic since biofilms contribute significantly to equipment degradation, including billions of dollars yearly in DoD assets , through corrosion, mold or increased drag, says DARPA.
For deeper understanding of Biofouling challenges and solutions please visit: Biofouling in Marine Environments: Challenges, Impacts, and Innovative Solutions for Marine Platforms
Biofouling is a significant and ongoing challenge for the DoD. Biofilms form extensively on
stored material, on aircraft and ship hulls, and in hard-to-reach places. Indeed, “microorganisms
can eat away at surface materials, and some of the worst areas affected are tight, hard-to-reach
areas that maintainers have difficulty disinfecting.”
In many cases, there is no simple remedy; the fouled surface or area cannot be easily accessed, as is the case for either the inside of fuel tanks or a deployed unmanned underwater vehicle (UUV). Current DoD remedies (scrubbing, dry docking, and fuel-tank draining for repair) have significant, long-term limitations; they must be continually applied at great expense, yielding diminishing returns.
“In FY2016 alone, corrosion cost the DoD over $20 billion1,” stated Dr. Paul Sheehan, Arcadia program manager. “The Arcadia program will focus on biofilm-mediated problems, including corrosion, that are both DoD relevant and tractable, enabling us to build the tools and understanding for biofilm management.”
In addition to reducing speed and maneuverability, marine biofouling can also interfere with the sensors and other systems on the UUV. As biofouling accumulates on the vehicle’s sensors and other critical systems, it can degrade their performance and accuracy, which can impact the UUV’s ability to carry out its mission.
Furthermore, marine biofouling can also have significant economic and environmental impacts. The accumulation of biofouling on the surface of UUVs and other marine equipment can increase fuel consumption and maintenance costs, and can also introduce non-native species to new environments, which can disrupt local ecosystems.
Biofouling on UUVs/gliders increases battery consumption via drag, similar to increased fuel usage of biofouled surface ships. This not only reduces UUV/glider deployment longevity, it also degrades their ability to navigate autonomously. Constant exposure to shear forces, shifts in the physical and chemical conditions between environments, nutrient availability, and the microbial ecology all influence the composition and stability of biofilms formed.
To address these challenges, the DARPA Arcadia program is exploring the use of “materiel probiotics” to combat asset degradation in military systems, including UUVs. By creating biofilms with beneficial microorganisms, the program aims to develop new coatings and materials that can protect military assets from degradation and other forms of damage caused by marine biofouling. The use of materiel probiotics is an innovative approach to addressing the problem of asset degradation in military systems, and could help to significantly enhance the durability and performance of UUVs and other marine equipment.
However, biofilms do not have to be a problem. New insights suggest biofilms could be rendered beneficial by redirecting their composition and structure. Similar to the Arcadian vision of harmony with nature, the DARPA Arcadia program will develop “probiotics” to protect military materials and equipment using naturally occurring microorganisms to generate robust and beneficial coatings, says DARPA.
Forming a stable and functional biofilm can be a balancing act since one is effectively creating a miniature ecosystem that acts like a living paint. Fortunately, recent advances in our understanding of how biofilms form and survive, combined with new tools for bacterial control, could enable the manipulation of a bacterial community toward a desired function.
The Arcadia program will focus on biofilm-mediated problems, including corrosion, that are both DoD relevant and tractable, enabling us to build the tools and understanding for biofilm management.”
- Drag on Unmanned Undersea Vehicles (UUVs) /Gliders,
- UUV/Glider Corrosion,
- Fuel-Tank Corrosion, or
- Black Mold Inhibition.
Arcadia will combat DoD asset degradation by generating “materiel probiotics” – biofilms with a beneficial function – via rigorous modeling of species interactions. This will require advances in the modeling of biofilm formation as well as high-speed microfluidic testbeds to grow, track, and test biofilms. Multiple strategies for biofilm generation will be examined, including assembly, where one starts with a single species followed by stepwise additions of new species and displacement, where one starts with a stable community and then displaces a problematic species with a preferred one.
The technology will be developed over two phases. During Phase I (24 months), performer teams will directly engage with Independent Verification and Validation (IV&V) partners, coordinated by DARPA, who will provide DoD-relevant biofilm samples. Performer teams will then develop high-throughput testbeds to characterize these samples and validate their models. During Phase II (24 months), performer teams will continue direct engagement with IV&V partners for community testing in the real-world. Communities must be stable and exhibit track-associated function after two months in the field.
The Defense Advanced Research Projects Agency has selected three university teams to develop protective biofilms designed to prevent the degradation of military assets.
DARPA said in March 2023 the Arcadia program aims to create beneficial materiel coatings using naturally occurring microorganisms to address biologically induced problems such as increased drag on unmanned undersea vehicles.
Clemson University will develop a stable microbial biofilm to decrease drag on underway UUVs as part of its Engineering Control of Organic Coatings on Autonomous Navy Gliders project.
Columbia University will work on its Inhibiting Molds with Probiotic Ensembles from Diverse Environments to identify and disseminate inhibitory organisms to safeguard military materiel and equipment.
Texas A&M University’s Microbes Achieve Resistance to MicroOrganism-influenced Rust was selected to develop methods of modeling and predicting microbially influenced rust to engineer a functional and resilient biofilm.
“Research has shown that accumulation of biofilms on UUVs can cause more than a 90% reduction in velocity within three months, leading to deployment failure,” said Tiffany Prest, Arcadia program manager.
“The Arcadia program aims to develop functional biofilms that not only inhibit costly microbial-induced corrosion but also can protect against it in the future,” added Sheehan.