Simple, Low‐Cost, Hydrophilic, and Permeable Sensors for Sweat Ascorbic Acid Detection with Screen‐Printed Carbon Electrodes and Flexible Wood Substrates

ABSTRACT Accurate detection of ascorbic acid (AA) levels is essential for diagnosing scurvy. However, traditional sweat‐based AA sensors are hindered by complex, costly electrodes, and weakly hydrophobic substrates. In this work, we present a novel approach to sweat AA detection using simple, low‐cost, and highly hydrophilic sensors fabricated from carbon electrodes printed on flexible, delignified wood substrates. The electrodes are fabricated by screen‐printing carbon ink, resulting in low‐cost, simple structures. The wood substrates are prepared through a delignification process, which enhances their flexibility and hydrophilicity, enabling direct sweat permeability due to the natural alignment of vessel channels in the wood structure. These fabrication methods and unique substrate structures give the sensors a high sensitivity (0.032 µA·L·µmol −1 ), excellent selectivity, a low detection limit (10 µmol/L), and a wide linear range (10–1000 µmol/L), along with a fast response time, and outstanding stability against mechanical bending, temperature fluctuations, and long‐term storage. Selective detection of ascorbic acid is achieved even in the presence of common interfering substances such as glucose and dopamine. Moreover, the sensors have been successfully tested on real human skin, demonstrating their potential for reliable real‐time monitoring of AA levels. These sensors could be applied in the prognosis, diagnosis, and management of scurvy.