CMOS-Based Multimodal Image Sensor Enabling Simultaneous Visualization of Light and pH

Conventionally developed pH image sensors are strongly affected by light. In this study, we developed a multimodal image sensor that can simultaneously measure light and pH and visualize each separately. We propose a method for multimodal sensing of light and pH by combining and arraying two types of pixels with different characteristics. The results of the characterization of a proof-of-concept device demonstrated that it can simultaneously measure two types of information with a pH measurement error of 10% and an optical measurement error of 8%. The proposed method enables pH imaging under light irradiation, whereas previously, it was possible only under dark environments. This has enabled applications in smart agriculture, where the sensor must operate under light irradiation. The method is expected to be deployed for real-time monitoring of ion information in plants, which was not previously possible.