Katerina Graf

Potassium activity in blood serum can indicate kidney disease, creating a demand for simple, biocompatible sensors for wearable devices that measure potassium activity. These potassium sensors are ion-selective electrodes (ISEs), which measure the potential difference across a polymeric membrane to determine the ion concentration in solution. ISEs have three important qualities: they have a predictable response to potassium, they maintain a stable signal over time, and they have high selectivity to potassium over sodium. High selectivity is required to prevent the larger concentration of sodium in blood serum from interfering with potassium measurements. Currently, commonly used polyvinyl chloride (PVC) ISEs exhibit these qualities, but they contain a toxic plasticizer that can leach from the ISE into the sample, making them poor candidates for use in wearable devices. Therefore, the current challenge is to develop a silicone-based ISE using commercial fluorosilicone and polydimethylsiloxane polymers. Silicone-based ISEs were prepared and characterized. The fluorosilicone-based ISEs had near-ideal responses to potassium, good selectivity to potassium over sodium, and moderate signal drift. The signal stability of the ISEs was increased by using porous carbon as a solid contact layer between the ion-selective membrane and the gold electrode. As another design, polydimethylsiloxane-based ISEs showed great promise for potassium measurement in clinical settings, as they had ideal responses to potassium and high selectivity.