A Miniaturized MgO Multi-Sensor Device Based on a Flexible Printed Circuit Board for Glucose and pH Detection

This study proposed a miniaturized multi-sensor device prepared using a flexible printed circuit board (FPCB) and applied to detect glucose (Glu) and pH value, where both the readout circuit board and the sensors possess flexible characteristics. Additionally, this work implemented the potentiometric readout circuit. It integrated the die onto the readout circuit board using wire bonding techniques, while the area of the readout circuit board is 5.5 cm $\times 4.0$ cm. The readout circuit board is equipped with a power supply, a readout circuit chip, and a multi-sensor. It is worth mentioning that this study designs the multi-sensor in a double-sided manner. The advantage of this design lies in the fact that both sides of the sensor can be utilized as a working electrode or reference electrode, providing convenience to users during measurement analysis. In addition, the magnesium oxide (MgO) multi-sensor is interconnected with the readout circuit board using slot type. This means the MgO multi-sensor can also be used as a disposable sensor. In this study, the multi-sensor system can measure hydrogen ions and Glu at the same time. The sensitivity of the two is 25.27 mV/pH and 16.78 mV/mM, respectively, and the linearity can reach 99.9 %.