Oxide semiconductor based deep-subthreshold operated read-out electronics for all-printed smart sensor patches

The ability to fabricate an entire smart sensor patch with read-out electronics using commercial printing techniques may have a wide range of potential applications. Although the solution-processed oxide thin film transistors (TFTs) are capable of providing high mobility electron transport, resulting in large ON-state current and power output, there is hardly any literature report that uses the printed oxide TFTs, at the sensor interfaces. In contrast, here we propose and demonstrate that printed amorphous indium-gallium-zinc oxide (a-IGZO) based deep-subthreshold operated TFTs can be used to fabricate an entire sensor analog front-end electronics comprising signal amplifiers, and analog-to-digital converters (ADCs), which can successfully digitalize the analog sensor signal up to frequency range of 1 kHz. In addition, exploiting the high current oxide TFTs, a current drive circuit has been designed, and placed after the ADC unit. This current drive circuit is essential to offer sufficient power output, which can then be used to fabricate an easy-to-detect visual recognition of the sensor signal at a predefined threshold value crossover. Notably, the entire smart sensor patch is demonstrated to operate at a low supply voltage of ≤2 V, thereby ensuring that it can be an on-chip, energy source compatible, and standalone detection unit.