Solid-State Chemical Microsensors for In-Place Monitoring of Total Acid Number (TAN) and Water Contamination in Oils, Hydraulic Fluids, and Fuels

Solid-state microsensors are very small, rugged, low cost, devices that can be highly sensitive to their chemical environment. Due to their unique capabilities, they have considerable potential as in- place sensors for engine condition monitoring, especially as real-time monitors of lubricants, fuels, and hydraulic fluids. This was recently demonstrated in a cooperative program with the Carderock Division, NSWC, that resulted in development of a Fuel Dilution Meter and a Total Base Number Meter for shipboard monitoring of diesel engine lubricants. In this proposed Phase I SBIR program, it is planned to design and evaluate other classes of chemical microsensors as specific monitors for total acid content (TAN) and water contamination using similar instrument design principles. The Phase I study will focus on two promising solid-state sensor technologies for determining the acid content of hydrocarbon fluids. These will be organic chemiresistors and adsistor type resistive films, both of which can be highly sensitive to changes in acidity of a contacting phase. Organic semiconductors are known to exhibit very large changes in conductivity with increasing hydrogen ion concentration, while the thin aluminum lines of an adsistor show large changes in resistivity due to acid induced corrosion. Surface Acoustic Wave (SAW) devices with water sensitive coatings will be evaluated as sensors for water contamination. A number of devices of each type will be fabricated and tested. Sensors with the best performance and physical properties will be selected for Phase 11 development of prototype shipboard monitors for water contamination and total acid content of petroleum based fluids.