A Smart Pen Based on Triboelectric Effects for Handwriting Pattern Tracking and Biometric Identification

The rapid development of artificial intelligence places high demands on human-machine interfaces. Various types of huma-machine interfaces have been implemented, including smart keyboards, electronic skins, and wearable motion sensors. Handwriting behavior has a high degree of interaction freedom, and handwriting characteristics offer high-security standards for human-machine systems. Herein, we propose a portable smart pen integrated with triboelectric displacement vector sensors to trace handwriting trajectories for human-machine interactions and biometric identification. A triboelectric pressure sensor array is evenly distributed along the pen case to sense displacement vectors, and an additional triboelectric sensor is placed on top of the pen to detect vertical force. By leveraging the resin pen refill as a tribopositive material and a nanowired polyethylene tribonegative layer attached to a Cu electrode, triboelectric signals are generated during the writing/moving process. The calculation and analysis of the sensor signals enable the recognition of handwritten patterns, including Latin letters and Arabic numerals. Moreover, the smart pen can be used to authenticate users based on their unique handwriting patterns, which can help take human-machine interfaces and cyber security to the next level. Furthermore, a custom smart pen operation mode that enables the control of a slide presentation demonstrates the smart pen's potential for various human-machine interface applications.