Wireless smart tag with potentiometric input for ultra low-power chemical sensing

The Internet of Things (IoT) envisions a future based on billions of smart connected devices. Devices that sense their surroundings and which when combined with cloud computing services will provide information on scales ranging from the microscopic to global. We demonstrate here for the first time the development and characterisation of an ultra low-power radio-frequency identification (RFID) wireless sensor tag with potentiometric input for use with pH and ion-selective electrodes. Tags such as this will be critical to the practical realisation of the Internet of Things. The tag is able to autonomously measure and store electrode potential in its internal memory, and then transfer logged data wirelessly by RFID to a nearby reader or by near field communication (NFC) to a smart phone. The unique features of the sensor tag include its ultra low-power consumption, potentiometric sensing ability, autonomous data logging, and RFID/NFC compatible air interface. These features make the tag suitable for use where pH or ion-selective electrodes are deployed as stand-alone chemical sensors or as part of larger chemical sensor networks that will underpin the IoT. pH determination in solution is used as an experimental example for illustrating measurement capability of the tag, and its analytical performance is compared to a standard laboratory pH meter.