ITO-based MEMS sensor electrode for dynamic cow-rumen pH sensing

A solid-type pH sensor for dairy cow-rumen measurement is developed. The pH sensor combines a metal-oxide-semiconductor field-effect transistor (MOSFET) with a separate sensing electrode made of indium tin oxide (ITO) film, which is a separate sensing component and connected to the gate terminal of the FET. The developed pH sensor offers the advantages of FET and ITO sensing techniques. The sensor system can be fabricated with a compact size by eliminating the reference solution. The solid-state sensor structure is fit for long-term pH measurement, and the separate ITO sensing electrode can be patterned with a suitable capture structure for cow-rumen test environment. The results show that the pH sensor has a <1 mA baseline for pH = 7 and >14 μA/pH measurement sensitivity. After good packaging, the solid pH sensor is adapted to sense the daily range of pH value of the rumen, and the developed sensor can help farmers efficiently monitor the health condition of wagyu cows.