Wearable paper-based potentiometric sensor for real-time detection of chloride ions in sweat

Herein, we report an office-paper-based potentiometric sensor integrated with a microfluidic paper network in an apple-like configuration, designed for continuous monitoring of chloride ions in sweat within a wearable platform. The paper-based device combines a chloride-selective membrane with a solid-contact, office paper-screen-printed transducer, and a capillary-driven paper-based microfluidic architecture, ensuring controlled sample delivery, minimising evaporation-induced drift, and eliminating memory effects, as confirmed by hysteresis studies. This work highlights the effectiveness of paper as a smart material for both sensing and sweat management in wearable electrochemical devices, achieving a sensitivity of 56 mV/log aCl⁻, a linear range of 1–200 mmol L⁻¹, and a detection limit of 74 µmol L⁻¹. Compared with the reference titration method, bias values ranged from −14% to +4%. These results pave the way for low-cost, disposable, environmentally friendly, and memory-free evaluation of electrolyte balance during physical activity, as well as for non-invasive diagnostics and monitoring highly effective modulator therapy in cystic fibrosis.