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Two types of urea biosensors were integrated with a wireless measurement system and microfluidic measurement system. The two biosensors used were (i) a magnetic beads (MBs)-urease/graphene oxide (GO)/titanium dioxide (TiO2)-based biosensor and (ii) an MBs-urease/GO/ nickel oxide (NiO)-based biosensor, respectively. The wireless measurement system work exhibited the feasibility for the remote detection of urea, but it will require refinement and modification to improve stability and precision. The microchannel fluidic system showed the measurement reliability. The sensing properties of urea biosensors at different flow rates were investigated. From the measurement results, the decay of average sensitivity may be attributed to the induced vortex-induced vibrations (VIV) at the high flow rate. In the aspect of wireless monitoring, the average sensitivity of the urea biosensor based on MBs-urease/GO/NiO was 4.780 mV/(mg/dl) and with the linearity of 0.938. In the aspect of measurement under dynamic conditions, the average sensitivity of the urea biosensor based on MBs-urease/GO/NiO were 5.582 mV/(mg/dl) and with the linearity of 0.959. Both measurements performed NiO was better than TiO2 according to the comparisons.

In this study, the potentiometric arrayed glucose biosensors, which were based on zinc oxide (ZnO) or aluminum-doped zinc oxide (AZO) sensing membranes, were fabricated by using screen-printing technology and a sputtering system, and graphene oxide (GO) and Nafion-glucose oxidase (GOx) were used to modify sensing membranes by using the drop-coating method. Next, the material properties were characterized by using a Raman spectrometer, a field-emission scanning electron microscope (FE-SEM), and a scanning probe microscope (SPM). The sensing characteristics of the glucose biosensors were measured by using the voltage–time (V-T) measurement system. Finally, electrochemical impedance spectroscopy (EIS) was conducted to analyze their charge transfer abilities. The results indicated that the average sensitivity of the glucose biosensor based on Nafion-GOx/GO/AZO was apparently higher than that of the glucose biosensor based on Nafion-GOx/GO/ZnO. In addition, the glucose biosensor based on Nafion-GOx/GO/AZO exhibited an excellent average sensitivity of 15.44 mV/mM and linearity of 0.997 over a narrow range of glucose concentration range, a response time of 26 s, a limit of detection (LOD) of 1.89 mM, and good reproducibility. In terms of the reversibility and stability, the hysteresis voltages (VH) were 3.96 mV and 2.42 mV. Additionally, the glucose biosensor also showed good anti-inference ability and reproducibility. According to these results, it is demonstrated that AZO is a promising material, which could be used to develop a reliable, simple, and low-cost potentiometric glucose biosensor.

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