Abstract
An implantable multi-ion image sensor equipped with magnesium ion (Mg(2+))-and calcium ion (Ca(2+))-sensitive membranes was fabricated for the selective measurement of extracellular Mg(2+) in the brain, and the sensor performance was evaluated. This sensor complements the low selectivity of the Mg(2+)-sensitive membrane for Ca(2+) by depositing a Ca(2+)-sensitive membrane in addition to the Mg(2+)-sensitive membrane on a CMOS (Complementary Metal Oxide Semiconductor)-based potentiometric sensor array with 5.65 × 4.39 µm(2) pitch, enabling selective measurement of Mg(2+) and Ca(2+). Characterization of the sensor confirmed a Ca(2+) sensitivity of 26.5 mV/dec and Mg(2+) sensitivity of 19 mV/dec. Based on validation experiments with varying concentrations of Mg(2+) and Ca(2+), selective Ca(2+) and Mg(2+) measurements were successfully achieved. Furthermore, real-time imaging of Mg(2+) and Ca(2+) and quantification of their concentration changes were performed. The developed sensor may be successfully applied for extracellular multi-ion imaging of Mg(2+) and Ca(2+) in the living brain.