A Scalable ISFET Sensing and Memory Array With Sensor Auto-Calibration for On-Chip Real-Time DNA Detection

This paper presents a novel CMOS-based system-onchip with a 78 × 56 ion-sensitive field-effect transistor array using in-pixel quantization and compensation of sensor nonidealities. The pixel integrates sensing circuitry and memory cells to encode the ion concentration in time and store a calibration value per pixel. Temperature sensing pixels spread throughout the array allow temperature monitoring during the reaction. We describe the integration of the array as part of a lab-on-chip cartridge that plugs into a motherboard for power management, biasing, data acquisition, and temperature regulation. This forms a robust ion detection platform, which is demonstrated as a pH sensing system. We show that our calibration is able to perform readout with a linear spread of 0.3% and that the system exhibits a high pH sensitivity of 3.2 μs/pH. The complete system is shown to perform on-chip realtime DNA amplification and detection of lambda phage DNA by loop-mediated isothermal amplification.