PNIPAM/PEDOT:PSS Hydrogels for Multifunctional Organic Electrochemical Transistors

Abstract The development of multifunctional organic materials represents a vibrant area of research, with applications spanning from biosensing to drug delivery. This study shows the development of a multifunctional bioelectronic device suitable for prolonged temperature monitoring and drug delivery applications. The device relies on a conducting and thermo‐responsive hydrogel made of poly(3,4‐ethylenedioxythiophene) doped with poly(styrene sulfonate) (PEDOT:PSS) and poly(N‐isopropylacrylamide) (PNIPAM). This multifunctional hydrogel is 4D printable by Digital Light Processing (DLP) method and exhibits optimal biocompatibility. The hydrogel features a low critical solution temperature (LCST) ≈35 °C, above which its resistance changes dramatically due to the shrinkage it undergoes with temperature. The integration of PNIPAM/PEDOT hydrogel into an organic electrochemical transistor (OECT) as the gate electrode allows to generate a miniaturized bioelectronic device with a reversible response to temperature variations between 25 to 45 °C, along with high sensitivity of 0.05 °C −1 . Furthermore, the PNIPAM/PEDOT hydrogel demonstrates its utility in drug delivery, achieving an Insulin‐FITC release rate of 82 ± 4% at 37 °C, mimicking human body conditions. The hydrogel's functionality to store and release the insulin does not compromise its thermo‐responsivity and the overall performance of the OECT. This multifunctional OECT opens new avenues for the development of customizable and personalized sensing and drug‐delivery systems.