ZeroPowerTouch: Zero-Power Smart Receiver for Touch Communication and Sensing in Wearable Applications

The human body can be used as a transmission medium for electric fields. By applying an electric field with a frequency of decades of megahertz to isolated electrodes on the human body, it is possible to send energy and data. Extra body and intra-body communication is an interesting alternative way to communicate vvirelessly in the new era of wearable device and internet of things. This promising communication works without the need to design dedicate radio hardware and with lower power consumption. We designed and implemented a novel zero-power receiver targeting intra-body and extra-body wireless communication and touch sensing. To achieve zero-power and always-on working, we combined ultra-low power design and an energy-harvesting subsystem, which extracts energy directly from the received message. This energy is then employed to supply the whole receiver to demodulate the message and to perform data processing with digital logic. The main goal of the proposed design is ideal to wake up external logic only when a specific address is received. Moreover, due to the presence of the digital logic, the designed zero-power receiver can implement identification and security algorithms. The zero-power receiver can be used either as an always-on touch sensor to be deployed in the field or as a body communication wake up smart and secure devices. A working prototype demonstrates the zero-power working, the communication intra-body, and extra-body, and the possibility to achieve more than 1.75m in intra-body without the use of any external battery.