Breathable, superhydrophobic and multifunctional Janus nanofibers for dual-mode passive thermal management/facial expression recognition with deep learning

With the rise of smart wearable electronics, there is increasing demand for multifunctional, high-performance flexible sensors that are breathable, anti-wetting, and comfortable. However, balancing these features remains a challenge. In this study, a composite thermoplastic polyurethane (TPU) and polydimethylsiloxane (PDMS) nanofibers were fabricated through one-step blending electrospinning, creating a TPU/PDMS nanofibers with adhesive overlapping structures and a uniform multi-component architecture at the nanoscale. This configuration enhances the properties of each material, achieving nanoscale synergy. Additionally, conductive multi-walled carbon nanotubes (MWCNTs) and silver nanowires (AgNWs) were embedded on one side, forming a Janus structure, yielding breathable, superhydrophobic Janus nanofibers (BSM-JNF) with a water contact angle of 160° and breathability of 333.1 mg/cm 2 /h. Naturally, by combining the properties of the composite nanofibers and the Janus structure, the BSM-JNF provides dual-mode passive personal thermal management. Its cooling side effectively reflects infrared light, reducing the skin surface temperature by approximately 3.7 °C compared to traditional cotton fabrics, while its heating side efficiently absorbs light, raising the nanofiber temperature by around 5.5 °C. Furthermore, it demonstrates impressive strain sensing capabilities (gauge factor of 86.9), with a wide sensing range (up to 202 %) and stable signal retention under temperature fluctuations, achieving multifunctional integration. Furthermore, the application of the BSM-JNF-sensor in facial expression recognition is demonstrated. Using deep learning algorithms and data preprocessing techniques, the BSM-JNF sensor achieved real-time, accurate human emotion recognition, even while worn under a mask, with a classification accuracy of 98.3 %. These findings underscore its potential as a key material for future smart wearable devices, offering new insights for developing multifunctional, high-performance wearable electronics.