An interdigitated impedance microsensor for detection of moisture content in engine oil

To address the need for the on-site measurement of aging oil, in this paper, we propose an impedance-based microsensor for analyzing the moisture content in engine oil. Using a microfabrication process, we fabricated an interdigitated microelectrode and integrated it with a 3D-printed microcontainer to produce a microsensor that can detect changes in the permittivity of oil. When the moisture content in oil increases, this sensor can detect the resulting change in the oil impedance, which is related to its permittivity, and then determine the degree to which the oil has aged. The test results show that the proposed microsensor has the advantages of being small and having high sensitivity, good accuracy, and the ability to be combined with hand-held instruments. The proposed method is expected to be used for the rapid, low cost, on-site determination of oil aging.