The Stability Analysis of Potentiometric Urea Biosensor Under Microfluidic System and Remote Measurement

Stability is one of the most important characteristics of the potentiometric urea biosensors; however, it has rarely been discussed in previous literature. In this article, the stability of the potentiometric urea biosensor based on the urease-Ag NPs/RuO
₂
sensing film was studied. Using the voltage–time (
$V$
–
$T$
) measurement system, the stability was verified by analyzing the biosensor’s reproducibility, repeatability, long-term measurement, and effect of temperature. Based on the results of this study, the proposed potentiometric urea biosensor had good reproducibility [relative standard deviation (RSD) was 2.23%] and repeatability (RSD was 1.16%). The urease-Ag NPs/RuO
₂
sensing film still has 90% initial sensitivity after 15 days of storage at room temperature. Moreover, the proposed urea biosensor was integrated into the microfluidic system and the remote measurement system. The sensing characteristics of the potentiometric urea biosensor under different flow rates (1.4–7.0
$\mu \text{L}$
/min, 0–30
$\mu \text{L}$
/min) were studied. In the remote measurement, the average sensitivity was 45.75 mV/decade and the linearity was 0.986.