Lubricants which are used in engines to reduce friction, promote engine cooling, and prevent corrosion degrade with time under harsh engine operating conditions and hence need to be changed periodically. Since degradation of oil is a result of number of mechanisms such as; engine component wear, oil oxidation, water ingress, and carbon particles, a versatile and microscopic in-situ sensor that can sense quality of wide variety of engine lubricant brands at various temperatures and pressures is of great need. This problem can be resolved by applying portable interdigitated micro-sensors to examine the impedance behavior of degraded lubricants through electrochemical tests. Electrochemical measurement techniques were used on both commercially available and custom built micro-sensors (fabricated through electron beam lithography) to understand impedance behavior of a mixture of oil, wear and additive particles, and other impurities at different environmental conditions. The impedance response of the oil was found to increase with a decrease in wear and additive metal ion concentrations, total acid number (TAN) and temperature. Based on the results obtained work is ongoing to improve the measurement sensitivity and create a sensor that can effectively detect the amount of degradation oil has experienced and to isolate the influence of multiple degradation mechanisms.
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