Sensing of Chloride Ions in Sweat by Means of Printed Extended‐Gate Organic Electrochemical Transistors

Abstract The accurate monitoring of chloride levels in sweat is crucial for diagnosing and managing cystic fibrosis (CF). The standard clinical approach is limited by the need for centralized, expensive, and labor‐intensive processes. To overcome such limits, cost‐effective wearable technologies allowing continuous monitoring are desirable. Toward such a goal, this study introduces a sensing platform based on inkjet‐printed extended‐gate organic electrochemical transistors (ExG‐OECTs) for the accurate quantification of chloride ions in sweat. The optimized ExG‐OECT achieves very good electrical performance, characterized by a high normalized transconductance, an on/off ratio >10 ⁵ , and excellent stability during prolonged operation. An Ag/AgCl electrode fabricated via chemical oxidation of an inkjet‐printed Ag electrode is employed as a sensing element and demonstrates remarkable sensitivity and selectivity for chloride ions both in simple chloride solutions and in artificial eccrine perspiration. The developed ExG‐OECT sensor demonstrates consistent and robust chloride ion detection across the physiological range, highlighting its significant potential as a powerful tool for non‐invasive, real‐time sweat analysis in wearable health monitoring technologies.