Hierarchical 3D-printed chitosan-based bioelectronic patches with enhanced sensitivity and eco-friendly disposability

Biodegradable wearable sensors have emerged as a crucial technology for sustainable health monitoring systems to address the growing concern of electronic waste in the Internet of Things (IoT) era. Conventional chitosan-based sensors have been investigated by several researchers but still confront significant issues of limited sensitivity, restricted surface area, and insufficient real-time monitoring capabilities. Here, we demonstrate high-performance biodegradable sweat ion sensors fabricated using hierarchical 3D printing of a chitosan-glycerol nanocomposite. The flexible chitosan patches adhere conformally to human skin and enable stable ion detection without mechanical degradation. The hierarchically structured sensors exhibit outstanding characteristics, including enhanced sensitivity (31.89% improvement), a 4.29 ± 1.1-fold increase in surface area (with an 18.9 ± 0.4-fold increase in pore volume), and excellent biocompatibility (> 90% cell viability). The feasibility of eco-friendly disposal is demonstrated through phosphate-buffered saline immersion, soil burial, and thermal incineration tests. Finally, the multi-ion sensing platform is applied onto human skin during physical exercise and operates with reliable real-time monitoring of Na⁺, K⁺, H⁺, and Cl⁻ biomarkers, establishing a new benchmark for green wearable electronics.