Wang Tengfei,Xu Guangning,Wu Wenyuan,Wang Xiaoying,Chen Xueliang,Zhou Shumin,You Fan
Nowadays, there is great interest in the use of microfluidic paper-based analytical devices (μPADs) for low-cost diagnostics. In most cases, the test equipment is needed. Here we report a new type of device-independent detection method based on timer-paper-based analytical devices, which can be tested by smartphone, and its application for cholesterol detection. The Quick Response code was designed as the timer component of this device. Wax printing method was employed to print the pattern on filter paper. The color and enzyme reagents have been immobilized in the hydrophilic channel to complete the colorimetric detection for cholesterol. Under laminar flow conditions of the cellulose network, the liquid volume of detection zone has been quantified by monitoring the fluid residence time on different area of the timer-paper-based devices. The precise monitoring of detection time can promote the accuracy of colorimetric detection. This is very important for the quantitative detection of paper-based analytical devices. One significant outcome of this report is that simple and accurate timer can be used for detection process self-clocking. The factors of total detection time have been investigated. The linear range of the calibration curve was 3.0 ~ 6.0 mmol L −1 , with correlation coefficient of 0.9956. With the characteristic of easy to use, low cost and accurate monitoring of detection time, this kind of timer-paper-based devices can be applied to cholesterol or other substances rapid detection.
Wearable sweat sensors are becoming increasingly popular for their robust capabilities in non-invasive, dynamic, and continuous real-time monitoring of biological information. Real-time monitoring of large-scale samples is crucial for realizing intelligent health. A major bottleneck for enabling large-scale sweat elucidation is the fabrication of wearable sensors equipped with microfluidic devices and flexible electrodes in a cost-effective, homogeneous performance and rapid large-scale way. Herein, a “Screen+Wax”-printing technique was introduced to prepare these components and construct “Lego Bricks” type wearable sweat sensor sensor to monitor sweat Na + and K + . Flexible electrode arrays and paper-based microfluidic layers (they act as building blocks) were fabricated on polyethylene terephthalate and paper surfaces, respectively, using screen printing and wax printing. Gold nanoparticles and Na + /K + ion-selective membranes were modified on the electrode surfaces by electrodeposition and drop coating, respectively. In this work, we highlight the excellent performance of the “Lego Bricks” type wearable sweat sensor in testing the Na + and K + imbalance of sweat from different body regions during exercise and, more significantly, to track the physical activity during prolonged exercise under different interventions. Furthermore, the prepared “Lego Bricks” wearable sweat ion electrochemical sensor is demonstrated to be capable of large-scale samples elucidation with outstanding performance and cost-effectiveness, which is expected to deeply integrate sweat monitoring into physical activity, providing an important tool for intelligent health.
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