A multi-parameter on-chip impedance sensor for the detection of particle contamination in hydraulic oil

TLDR: In this article, a multi-parameter sensor based on microfluidic chip is presented, which consists of a planar coil and a metal wire inserted into the center hole of coil.

Abstract: A multi-parameter sensor based on microfluidic chip is presented. The sensor consists of a planar coil and a metal wire inserted into the center hole of coil. It can be used as an inductive sensor or capacitive sensor, so multiple parameters can be detected on one sensor. The vertical channel effectively prevents the clogging of the microchannel, reducing the detection error and improving the service life of the detection chip. The related experiments were carried out on the built detection system, which proved the annular microchannel can force that the metal particles pass through the most sensitive region, therefore the sensitivity of inductance detection is enhanced. And the cross-sectional area of the microchannel increases, so the throughput is higher. For the inductance detection, the signal-to-noise ratio initially increases with the coil turns, but then it has a tendency to decrease. For the capacitance detection, the signal-to-noise ratio decreases with the coil layers. We used the coil with 40 turns, which can ensure the detection sensitivity of the inductance detection and the capacitance detection, to explore the floor level of chip. We successfully detected 40 μm iron particles, 125 μm copper particles, 60 μm water droplets and 120 μm air bubbles.