CMOS-Based Multimodal Image Sensor Enabling Simultaneous Dissolved Oxygen and Hydrogen Ion Measurement

We report the world's first CMOS multimodal image sensor that measures dissolved oxygen (DO) and hydrogen ions (H+) by patterning an iridium oxide (IrOx) film on a potentiometric sensor array with a titanium nitride (TiN) electrode. IrOx, which functions as a DO-sensitive membrane, was patterned on the pixel array using semiconductor photolithography. The resulting sensor showed a sensitivity for the DO of 40 m V /Iog[ O<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>] ppm on the IrOx patterned regions and the H<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> response of 59.4 mV /pH on the TiN electrode. We successfully demonstrated two-dimensional DO and H+ imaging on the fabricated sensor for the first time.