Live demonstration: An NFC based batteryless CMOS ISFET array for real-time pH measurements of bio-fluids

We demonstrate a low-power CMOS ISFET array for pH sensing which is inductively powered using NFC. Each pixel in a 3-by-3 array contains an ISFET operating in weak-inversion which detects changes in pH as a current. The output of all pixels is then averaged and converted to a frequency using a current-starved ring oscillator. We make use of a commercial NFC IC, the SIC4310, to harvest power from a standard smartphone and power the ASIC, which consumes up to 6 pW. The output frequency of the ASIC is then transferred to the phone to provide a real-time measurement of pH from a batteryless platform.