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

Abstract

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 (It = 600 s) for the Reference Device (average) reduce to a value of 44.8 nA (It = 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.

Recent Developments in Printing Flexible and Wearable Sensing Electronics for Healthcare Applications

“…Graphene-based tattoos are patterned in serpentine structures through a wet-transfer dry-pattering approach. Organic materials containing a linked chain of crown ether were printed as Na + -binding elements for the development of a simple hydration sensor [ 119 ]. The ideal polymeric molecule containing a linked chain of crown ether is poly[(dibenzo-18-crown-6)-co-formaldehyde], which was evaluated by comparing the device characteristics with a reference device without the crown ether.…”

Manipulating nanoscale structure to control functionality in printed organic photovoltaic, transistor and bioelectronic devices

“…The comparatively straightforward synthesis and availability of monomer has for some time positioned P3HT among a limited group of donor polymers that are suitable for the large-scale commercialisation of OPVs [66]. The hole mobility of P3HT has been shown to be tunable across the range of 10 −4 -10 −1 cm 2 V −1 s −1 by controlling the molecular weight [66,67], regioregularity [68] and interchain polarity through organic acid dopants [69], leading to applications in transistors and sensors [70] where the output sensitivity is dependent on these doping mechanisms. Electroactive P3HT inks have also been shown to have their electronic and ionic conductivity modulated by the local humidity and polyionic additives [71].…”

“…Because the organic semiconductors are so susceptible to small changes in ionic dopant content, they act as voltage transducers with low bias voltages (∼1 to 10 V) and very high sensitivity which can be modulated by controlling the nanostructure of the dielectric using the solvent washing technique described in the previous section. At the University of Newcastle, we have previously demonstrated printable organic biosensors based on both an enzyme-containing OTFT for glucose sensing [123], and a crown-ether-modified chemiresistor for sodium ion sensing [70] that operate on the same principles. The group of Bortolotti has demonstrated the successful fabrication of a tumour necrosis factor alpha (TNFα) sensors using anti-TNFα as a recognition element grafted on to the gate electrode of the transistor [241], while Magliulo et al demonstrated another similar type of device, this time with the recognition element (anti-C-reactive protein monoclonal antibody) bound to the semiconductor layer rather than the gate electrode [242].…”