Integrated interface circuits for chemiresistor arrays

Integrated circuits customized to transduce resistance information from small footprint composite polymer chemiresistor arrays are presented. The circuits are designed to fit underneath the sensor platform itself, therefore enabling 100% fill factor of the chemically active area as a percentage of total sensor surface area. Two approaches to transducing very small changes in resistance on top of a large baseline resistance are presented. Both seek to transduce small changes in resistance, typical to composite polymer chemiresistors in practical applications, to a usable output with high sensitivity, detection limit, and resolution. The circuits have been simulated, fabricated, and tested in an integrated array underneath an array of sensor platforms in a CMOS process. Resolution for the resistance-to-digital circuit exceeds the noise characteristics of the chemiresistor while the resolution for the resistance-to-frequency circuit allows for the detection of changes in resistance as low as 0.02% of the baseline resistance.