Chip Scale Oceanographic Sensor

To protect against corrosion, a ship’s Impressed Current Cathodic Protection (ICCP) system distributes electrical energy between sections of the hull. The ICCP control system measures voltages using seawater silver/silver-chloride reference electrodes and adjusts the electrical potentials appropriately. Because changes in seawater chemistry near the hull will change the electrical potentials, there is a need for real-time oceanographic measurements that the ICCP can use to provide feedback control to the ICCP.   In this project, TDA is developing a concept and design for a chip-scale oceanographic sensor that can be integrated onto a ship, submarine, or unmanned underwater vehicle (UUV) hull to accurately measure ocean water chemistry in real-time. TDA’s design uses solid state devices including miniaturized electrodes, control circuitry, and sensors that are affordable and can be mass produced using screen printed manufacturing techniques. Our sensor device (3” x 3” x 1.7”) will make highly accurate measurements of T, pH, conductivity, TDO (total dissolved oxygen), as well as the concentrations of chloride, sodium, calcium, and other relevant ions.   In Phase I we acquired (or had custom fabricated) multiple sensors, and tested their ability to measure conductivity, pH, dissolved oxygen (DO), pressure, and ion concentrations of K+, Na+, and Cl-. We tested them over a temperature range of 2-50°C, a pressure range of 0-1,000 psi, and a pH range of 4-10. We also tested them over longer periods of time (hours to days) to measure the sensor drift, and identified the reasons for the drifts so that they can be compensated.  We also tested the sensors in the presence of known contaminants such as presence of other ions: calcium, chlorides, sulfates, nitrates, and sulfides.   In Phase II we will further develop and demonstrate our prototype under the necessary environmental stresses, including one month in a natural seawater environment where biofouling colonization is prevalent. In the Option One, we will modify the device designs so they can be integrated into the shipboard ICCP reference electrode holder and demonstrate its performance in seawater and its integration with an ICCP electrode. Certification of the seawater tests will be conducted by the Naval Research Laboratory and Naval Surface Warfare Center, but the testing and evaluation will be conducted by TDA Research. In the Option Two, we will fabricate, and deliver two prototypes that are integrated with ICCP control system to support the Navy in transitioning the technology for Navy use through system integration and qualification testing.