Insertable 256×256 ion image sensor for spatiotemporal pH recording

In vivo neural imaging devices are developed not only to record chronically but also to obtain the spatiotemporal information of neurochemical signals. Here, we present an image sensor consisting of a 256 × 256 pixel array and an integrated readout circuitry for a biomedical implantation application. The key idea of this sensor is that a higher resolution array than that of our previous insertable sensor realizes by employing two transistors in our pixel circuit. The proposed sensor architecture was fabricated by a modified 1P4M 0.15 μm CMOS process. This sensor was able to detect a hydrogen ion distribution change during the inserting test carried out at a brain-like object, and to reproduce the measured data into a two-dimensional (2D) image series in real-time.