Simple Solution Processed Solid‐State Organic Transistor Chip for Multi‐Ion Sensing

Abstract Ion concentrations in the human body are closely tied to crucial biological functions and thus serve as important diagnostic health markers. Biological samples are chemically complex, containing a wide range of ions and molecules, necessitating the use of sensors that are highly selective to the target analyte. In this work, a multi‐ion sensing chip, capable of selectively detecting potassium (K + ), sodium (Na + ), and calcium (Ca 2+ ) ions at physiologically relevant concentrations, is demonstrated. Each sensor consists of a simple, solution‐processed, all solid‐state, and low‐voltage organic thin film transistor, functionalized with polyvinyl chloride (PVC) ion selective membranes sandwiched between the insulator and gate electrode. The sensors are responsive to 4–5 decades of each primary ion. When a response from interfering ions is seen at higher concentrations, the sensors can uniquely discriminate between primary and interfering ions by a difference in the polarity of the current modulation. The sensors function well in mixed‐ion solutions, and can detect K + , Na + , and Ca 2+ in simulated human blood serum, demonstrating the feasibility of using these devices for the analysis of complex analytes. This work represents an important step toward the development of simple, inexpensive organic multi‐ion sensors.