Battery-Free Identification Token for Touch Sensing Devices

This paper proposes the design and implementation of low-- energy tokens for smart interaction with capacitive touch-- enabled devices by associating the token's identity with its contact, or touch. The proposed token's design features two key novel technical components: (1) a through--touch--sensor low--energy communication method for token identification and (2) a touch--sensor energy harvesting technique. The communication mechanism involves the token transmitting its identity (ID) directly through the touch--sensor by artificially modifying the effective capacitance between the touch-- sensor and token surfaces. This approach consumes significantly lower energy compared to traditional electrical signal modulation approaches. By enabling the token to harvest energy from touch--screen sensors or touch--surfaces the token is rendered battery--free. Through experimental evaluations using a prototype implementation, the proposed design is shown to achieve at least 95% identification accuracy. It is also shown to consume less energy than competitive techniques (NFC P2P and Bluetooth Low--Energy) for communicating a short ID sequence. The adoption of this technology among users is evaluated through a user study on 12 subjects.