High-resolution real-time ion-camera system using a CMOS-based chemical sensor array for proton imaging

We describe a complete lab-on-a-chip type ion-sensitive chemical sensor array system for imaging proton concentration and flow. The core of the imaging system relies on a 715.8 μm × 715.8 μm large 64 × 64-pixel ISFET sensor array that is designed and fabricated in a conventional 4-metal 0.35 μm CMOS process along with readout circuitry and additional electronics. The high-speed and real-time data acquisition of ∼100 frame per second (fps), 40 μs per pixel, results in a large amount of data that is streamed to the hard disk. Image reconstruction methods allow visualization of the dynamic behavior of chemical substances and ionic spreads over the sensor array at a resolution of the size of a pixel. The functionalities of the on-chip ion-camera device are demonstrated using appropriate acid and alkaline solutions. A pH sensitivity of 20 mV/pH was achieved without modification to the foundry processed chip.