Imec and Holst Centre, two sister research organizations based in Belgium and Holland, unveiled a tiny sensor for measuring a fluid’s pH and chloride levels. Chloride is an electrolyte involved in a variety of cellular processes, including regulating the body’s pH level. Being able to measure these parameters may make them popular metrics for assessing athletic performance and for personalized medicine.
The new sensor and supporting components are integrated into a unified chip. It’s small enough to be embedded into other devices, such as activity trackers, for example.
The major technological challenge was creating an electrode that remains stable and does not skew results over time. There are two electrodes within this type of sensor. One is an ion-sensitive electrode that has a membrane, and a reference electrode. Electric potential is produced when the electrodes are immersed in an ion-rich fluid, the intensity of which is proportional to the ion concentration. The problem is that reference electrodes that are as tiny as required in such a small device are typically unstable and eventually begin attenuating the signal.
According to Marcel Zevenbergen, a senior researcher on the project, overcoming these limitations involved creating a reference electrode that has a microfluidic channel as junction and solid-state iridium oxide (IrOx) and silver chloride (AgCl) electrodes on a silicon substrate. The two types of electrodes are optimized for measuring the pH and chloride, respectively.
The team tested the new sensor and showed that it remains stable over an extended time, providing accurate readings quickly and at high sensitivity.