Organic electronics incorporating crown ethers as Na ⁺ binding elements, towards a simple printable hydration sensor

Here, we present the development of organic electronic sensors containing crown ethers as ion binding elements for application in Na + detection for health monitoring. The design, fabrication and characterization of chemiresistor‐based sensors using simple solution processing methods amenable to printing were demonstrated. The analyte testing comprised aqueous solutions of sodium chloride (0, 20, 50, 80 and 130 mM), with the Na + concentration reflecting the range which occurs in human sweat. The introduction of the crown ether binding sites into the sensors was an iterative process, with three types of molecules trialled. The most effective molecule was found to be poly[(dibenzo‐18‐crown‐6)‐co‐formaldehyde], a polymer which comprises a linked chain of crown ether subunits. The binding of Na + ions to the crown ether sites of the polymer was measured by comparing the amperometric characteristics of devices without crown ether binding sites (Reference Device) to those with crown ether binding sites ( CE Device), following exposure to an analyte solution. For an 80 mM Na + analyte solution, we observed a sensor response of 116.2 nA ( I t = 600 s ) for the Reference Device (average) reduce to a value of 44.8 nA ( I t = 600 s ) for the CE Device (average). This sensor shows a proof of concept towards low‐cost, solution‐processable sodium ion sensors suitable for mass production on flexible substrates.