Improving Robustness, Sensitivity and Simplicity of Potentiometric Sensors Through Symmetry and Conceptual Design

It is an enormous challenge to bring chemical sensing concepts from a controlled laboratory setting into the field while maintaining accuracy. In an environment of uncontrolled, fluctuating temperatures and a lack of repeated calibration, sensor reliability can rapidly deteriorate the accuracy. Today, many sensing concepts are explored for home use or as wearable sensors, and it is paramount to understand and optimize the chemistry for reliable measurements to become possible. This review focuses on the well-established class of potentiometric sensors, mostly known for the measurement of pH, with a range of electrolytes, and how conceptual advances can be used to make them as robust and sensitive as possible. While drawing from recent work of the group at the University of Geneva, the importance of symmetry is stressed to minimize the influence of temperature. The development of self-powered sensing systems that no longer require a battery is explained. This is then connected to protocols in which the sensitivity of these sensors can be reliably improved beyond that dictated by the Nernst equation.