Long‐Term Stability of WS ₂ ‐Coated Textile‐Based Triboelectric Sensors for Self‐Powered Sweat Detection

ABSTRACT

Reliable self‐powered wearable sensors are essential for sweat monitoring but often face challenges in long‐term stability under physiological conditions. This study reports a WS ₂ ‐functionalised textile triboelectric nanogenerator for self‐powered sweat sensing, focusing on ageing and environmental robustness of the sensing layer. The device is fabricated via scalable ultrasonic spray coating of two‐dimensional WS ₂ nanosheets onto polyester, forming a flexible sensing interface capable of converting mechanical energy into electrical signals. Systematic evaluation under ambient ageing, humidity, and exposure to phosphate‐buffered saline (PBS) as a sweat‐mimicking fluid, conducted over timescales ranging from hours to months after fabrication, reveals that sensing performance depends on the counter‐triboelectric material, with WS ₂ / polyethylene‐terephthalate (PET) interface exhibiting superior stability. While freshly prepared devices show variable responses, short‐term ageing stabilises the electrical output, enabling reproducible sensing. Upon exposure to PBS, the WS ₂ /PET interface demonstrates consistent, volume‐dependent reduction in electrical output, confirming its capability for self‐powered sweat detection. Morphological, compositional, and wettability analyses reveal that long‐term performance is governed by progressive oxidation of WS ₂ and a transition from hydrophobic to hydrophilic surface states. These findings provide critical design guidelines for material selection and interfacial stability, informing the design of robust, self‐powered textile‐based biosensing systems for long‐term wearable applications.