Real-time facial micromotion tracking enabled by an ultrathin silk fibroin patch.

Driven by the rapid development of green wearable electronics, increasing attention has been directed toward environmentally sustainable and biocompatible piezoelectric devices based on natural biomaterials. Nevertheless, the inherently low piezoelectric performance of natural biomaterials remains a critical challenge for their application in high-performance wearable sensing. In this paper, a fully green bioelectronic piezoelectric film was developed, and a soft, ultrathin, and biocompatible silk fibroin-based piezoelectric patch sensor was fabricated using microfabrication techniques. By employing glycine as an indirect structural inducer, the secondary structure of silk fibroin was effectively regulated to enhance molecular alignment and β-sheet content, resulting in a significant improvement in piezoelectric performance. Simultaneously, calcium ion coordination modulated the Young's modulus to optimize flexibility and mechanical compatibility with skin. Compared to conventional natural piezoelectric films, the resulting patch sensor exhibits superior softness, micron-scale thickness, heightened force sensitivity, and stable signal response. Leveraging this sensor, a wireless facial micromotion monitoring system was developed, enabling dual-channel, real-time tracking of rapid eye movements and nasal flaring during sleep. Owing to its excellent conformability to the eyelid and nasal alae, the fully biocompatible system supports continuous, unobtrusive sleep monitoring and demonstrates strong potential for next-generation sustainable bioelectronic platforms in long-term health applications.