University of Illinois

Dongming He

Mark A Shannon

A thin film integrated conductivity sensor is formed on a suitable surface for measuring the electrical conductivity of a liquid. The surface is preferably an insulator, but may be conducting, if the electrodes are on an insulating surface. A preferred embodiment insulates the electrodes by use of a dielectric layer that is deposited on top of a silicon wafer substrate. A sensor tip is integrated on the top surface of the substrate. In a preferred embodiment, the substrate is fabricated into a sensor shape with a small sharp tip at one end and an opposite larger end for accommodating electrode pads. The larger end might also be used for integration of measurement circuits or accommodating bonding pads. In a preferred embodiment, the tip also accommodates an integrated temperature sensor to enable local temperature measurements. The sensor is a thin-film resistor preferably enclosed within a layer of the sensor tip and having a serpentine shape to produce significant resistance (hundreds to thousands of Ohms) while consuming a small area of the sensor tip.

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Chandler, AZ, United States of America

Dongming He