A Miniaturized ISFET-Based Blood pH Sensing Device for Home Care Use

This article presents the design of a miniaturized, minimally-invasive blood pH sensing device for medical point-of-care applications. Blood pH is a vital marker for determining respiratory and metabolic health. Abnormal blood pH levels indicate that the body’s natural buffer system is out of balance, which may imply serious health issues, such as kidney damage, pneumonia, or heart failure. This work utilizes an Ion Sensitive Field Effect Transistor (ISFET) to measure the pH of a liquid solution with a future focus on blood pH measurements. We designed a readout circuit to convert the changing threshold voltage of the ISFET, based on the solution’s pH level, to a pH measurement displayed on the device’s screen in real-time. With its portable size and its ability to accurately measure with a minimal amount of solution, this device may be a more convenient alternative for home use when compared to the current state-of-the-art blood pH measurement techniques.