Flexible Interdigitated Electrode-Enabled Electrochemical Impedance Spectroscopy for Detecting Diesel Contamination in Lubricating Oil

The health status detection of lubricating oil is crucial for the early diagnosis and screening of mechanical damage. This study introduces a flexible interdigitated electrode (IDE)-based electrochemical impedance spectroscopy (EIS) detection method. By analyzing the impact of electrode constants and geometric parameters on detection sensitivity, multiple IDE configurations were designed and fabricated via physical vapor deposition on polyethylene naphthalate (PEN) films for EIS-based assessments. Experimental results demonstrated a significant decrease in impedance magnitude within the $10-10^{3} \mathrm{~Hz}$ frequency range as diesel contamination levels increased, confirming the effectiveness of the flexible interdigitated electrode in detecting diesel-polluted lubricating oils through EIS, and an optimal IDE configuration with the highest sensitivity to contaminant concentration variations was identified. The flexible substrate ensures robust adaptability to dynamic environments and stable physicochemical properties, offering promising potential for in-situ industrial monitoring applications.