Here, we report a novel biosensing system using a finger‐powered microfluidic device, which is suitable for daily self‐testing of uric acid in saliva. To realize the rapid determination of salivary uric acid, the biosensing system measures directly from the paper‐based saliva sampling device. The microfluidic device has the diaphragm pump, the reagent reservoir, and the reaction cell in which the electrochemical uric acid biosensor is embedded. Once the microfluidic chip has been folded, the finger‐powered microfluidic device prepares the reagent containing the saliva, which is ready to measure. A wireless potentiostat for electrochemical measurement of uric acid with the biosensor was also developed. Combining these elements together, the whole process from saliva sampling to determination was completed in less than a minute (Sensitivity: 0.03 nA/μM). The measurement results were also consistent with that measured using a commercially available uric acid determination kit. Hence, our method is expected to have the potential to enhance the use of biochemical information in the field of healthcare IoT.

We investigated the preparation of Ga2O3 thin films using a wet-process and the Sn-doping conditions to improve resistivity. Undoped and Sn-doped single layer Ga2O3 thin films were prepared by changing the solution concentration, the annealing time, the temperature rise rate, and the rotational speed during deposition. As a result, they were deposited uniformly with good crystallinity and transmittance and relatively small surface roughness. To improve the resistivity by another Sn-doping method, we prepared bilayer samples consisting of undoped Ga2O3 and SnO 2 layers in which Sn atoms can diffuse into the Ga2O3 layer by annealing: the drive-in diffusion method. Although the resistivity was changed, XPS and TEM-EDS measurements revealed that Al diffused from the sapphire substrate, indicating a mixed β-(Ga,Al)2O3 was prepared. By varying the annealing temperature to 800°C, Al diffusion was suppressed and pure Ga2O3 thin films were prepared. After investigating various atmosphere sintering conditions, we found that the samples sintered in a nitrogen atmosphere for both Ga2O3 and SnO 2 showed the lowest resistivity.

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Diabetes is a typical lifestyle-related disease and blood glucose measurement plays an important role in daily health management and appropriate treatment for patients. Continuous glucose monitoring system (CGMS) is becoming common for general patients. In this paper, an optically-powered battery-less glucose sensor device with a 12mm diameter is presented. The sensor is expected to be used for next-generation CGMS. The sensor is equipped with series-connected ultra-small photovoltaic cells as the power source. Circuit design and characterization, fabrication and evaluation of a wireless sensor device are presented to demonstrate the feasibility of the proposed sensor architecture.