Capacitive Oil Detector Using Hydrophobic and Oleophilic PDMS Sponge

Abstract

In this study, we designed and fabricated a capacitive oil detector using a polydimethyl siloxane (PDMS) sponge and evaluated its performance. A PDMS sponge has a hydrophobic/oleophilic characteristic, which blocks water infiltration yet absorbs oil. The absorbed oil changes the detector capacitance between the two electrodes within the PDMS sponge. We used three primary types of marine fuel oils (diesel, crude oil, and heavy oil) to evaluate the performance of the fabricated oil detector. Diesel was detected in the shortest time, followed by crude oil and heavy oil. That is, oils with lower viscosity were detected more rapidly. The measured capacitance was the lowest for diesel and the highest for heavy oil. Oils with higher dielectric constants had a higher measured capacitance. Water did not seep into the microcavity of the capacitive oil detector until it reached a depth of 140 cm. We were able to detect the presence of an oil-film below 900 μm. The fabricated detector showed almost the same capacitance throughout the ten cycles of repeated cleaning and measurements.