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Matthew Argueta, Lindy Avila, Karla Covarrubias, Caden Milan, Lily Rieman

Department of Mechanical and Aerospace Engineering

University of California San Diego

Sponsored by Professors Eugene Pawlak and Drew Lucas

Background

Antibiofouling System for Moored Marine Instruments

Figure 2: Compromised CTD data due to biofouling (Pawlak)

Discussion

References

Acknowledgements

Biofouling is the biological growth of microorganism on surfaces submerged in marine environments. Biofouling starts to become visible as soon as three days after an instrument is deployed into the ocean. Once biofilm attaches to the surface, instrument data can become skewed. The team’s design focuses on preventing growth on an RBRconcerto³ CTD sensor which measures conductivity, temperature, and depth through water passing through the cylindrical inductive cell. The CTD is attached to a wirewalker which continuously moves up and down along a wire sampling data only on the ascent.

• Industry solutions include: mechanical wiping systems, biocidal coatings, UV light, and ultrasonic vibrations
• Team design inspired by the miniWIPER (Figure 3)
• Wiping system is efficient for a flat plane (Figure 1)
• Geometry of CTD requires a unique solution

• Professors Geno Pawlak & Drew Lucas – Project Sponsors
• Professor Jerry Tustaniwskyj – Faculty Advisor
• Yifei Zhang – Teaching Assistant
• Ed Pogue, Steve Roberts, Tom Chalfant – Technical Support
• Riley Meehan & Ryan Craft - Scripps Makerspace Directors

1. Pawlak, E. Ocean sensor maintenance. University of California, San Diego.
2. RBR Global. (n.d.). RBRduo³ & RBRconcerto³: C.T, C.T.D, C.T.D++ | Ocean CTD. https://rbr-global.com/products/standard-loggers/rbrduo-ct/
3. Precision Measurement Engineering. (n.d.). Anti-fouling water sensor WIPER. https://www.pme.com/products/wiper
4. K&J Magnetics DD44-N52 Pull Force https://www.kjmagnetics.com/largergraph.asp?CI=3&pName=D44-N52

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• Pressure Housing Parts sourced from Blue Robotics
• Boutique end cap for magnetic coupling

Figure 3: PME anti-fouling WIPER that is used in industry.

• External pressure of 17.5 atm and Internal pressure of 1 atm
• Unsupported disk diameter is 19.5 mm
• 6061 Aluminum plate of 1.5 mm thickness.
• Stress FOS: is 2
• Expected plate deflection less than 0.1 mm at 175 m depth

Conclusion

To advance this antifouling system toward real-world deployment, it is recommended that the waterproofing and mechanical resilience be validated through extended-duration and depth testing. Additionally, the final design should transition from 3D-printed components to machined or molded materials for improved durability and manufacturability. By reducing data degradation caused by biofouling, this technology supports global oceanographic research efforts and contributes to the protection of marine ecosystems. Compared to traditional methods like copper coatings and UV-based solutions, this system offers a more sustainable and environmentally responsible approach to maintaining sensor performance.

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Figure 1: Biofouled instrument (left) vs wiped instrument (right)

• Developed a vibration brushing system using only ~0.26 Wh/day
• Targets biofilm on RBRconcerto³ CTD sensor
• Lab tested for waterproofing
• Safer alternative to chemical coatings
• More power efficient than UV-based antifouling methods
• Optimized for complex geometry of the sensor
• Ocean testing still pending for long-term validation

Figure 4: RBRconcerto³ CTD sensor

Design

Objective

• Objective: mechanical anti-biofouling solution for instruments on the Wirewalker (a wave-powered vertical profiler)
• Constraints: harsh marine environment, power availability, complex geometries, sensitive/fragile components
• Prioritize sustainability, avoid harmful environmental impacts, and maintain the functionality of deployed instruments

Results

Figure 6: Front View of Design

• Initial ANSYS simulation (top) showed 3 mm of total deformation
• Added second arm to hold housing and thickened arms
• Final ANSYS simulation (bottom) shows total deformation of 1 mm with 2x the force

Figure 10: Left Magnet pull force; Right Magnetic Coupling Spacing

Figure 8: ANSYS Simulations of Pressure Housing Arm Designs for Total Deformation

Figure 12: Conductivity Interference for Calibrated Guard vs Antifouling Guard

Figure 5: Design Iterations

• Initial research focused on ultrasonic transducers and UV light
• Original design based on ultrasonic vibration
• Pivoted to a mechanical approach, lever-arm brush → timing belt system
• Added support arm to secure pressure housing

Key Design Components:

• Cleaning Mechanism → Timing Belt with Vibrating Brush
• Cleaning Unit → Nylon Brush
• Vibration Unit → Waterproof Vibration Motors
• Motor Drive Unit → Stepper Motor + Magnetic Coupling
• Pressure Housing → Blue Robotics

• Axial magnetic coupling
• Manufactured outer and inner rotor
• N-52 magnets sealed into rotors
• Pull force of a magnet is 0.48 lb at 4.2 mm.

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Figure 11: Roark’s Equation of Simply Supported Disk

where:

p: Net pressure difference

a: Unsupported radius

𝑣: Poisson's Ratio

t: plate thickness

E: Young's Modulus

Figure 9: Pressure Housing Internal View

Distance (in)

Pull Force (lb)

Conductivity

Time (min.)

5

10

15

20

25

4.2 mm

Meters

Meters