Finger temperature-driven thermogalvainc gel-based smart pen: Utilized for identity recognition, stroke analysis, and grip posture assessment

Inappropriate pen-holding postures can result in increased muscle strain and reduced writing speed, and may even contribute to the onset of conditions such as myopia, arthritis, and cervical spondylosis. However, challenges persist in current one-size-fits-all pens toward actively monitoring handwriting habits due to structural complexity and indispensability of power supply. In this study, a finger temperature-driven thermoelectric gel-based smart pen has been invented for identity recognition, stroke analysis, and grip posture assessment by coupling thermogalvanic and piezoresistive effects derived from finger temperature and pressure on a PVA/gelatin gel. This dual-network gel exhibits not only a high thermopower of − 2.05 mV K−1 and a rapid response of 130 ms, but also full flexibility, significant resistance to desiccation, and a high tensile capacity of up to 300%. By integrating thermogalvanic gel units within a pen shaft, our self-powered smart pen achieved a recognition accuracy of 98.1% for eight basic Chinese character strokes with the aid of deep learning. Furthermore, with a four-channel expansion, the recognition accuracy reaches 98.8% for eight distinct identities and 99.1% for nine different pen-holding postures, respectively, while offering real-time visualization of monitoring results on a user-friendly human-machine interface. This machine learning-assisted self-powered smart gel pen presents a new viable solution for wearable bioelectronics toward future intelligent era.