Yang Wang,Dingding Ye,Yang Xu,Xun Zhu,Yang Yang,Rong Chen,Qiang Liao
Electrochemical paper-based analytical devices (ePADs) are an excellent choice to achieve the goal of global health due to their advantages of low cost, portability, and rapid analysis. However, the low sensitivity limits the application of ePADs. In this study, a 3D origami-inspired ePAD with flow-through electrodes and quasi-steady flow was presented for signal amplification to enhance the sensitivity. A Silhouette Studio plotter/cutter was used to design four schemes with a porous gold electrode as the working electrode. The flow-through electrode with quasi-steady flow exhibited the highest current due to enhanced convective transfer. The peak current of the device combined with flow-through porous electrodes with flow increased by 97.2 and 63.8% compared with the device without flow and the device combined flow-over electrodes with flow, respectively. The finite element simulation results showed that the current increased 10 times compared with the conventional saturated devices with flow-over electrodes and flow-through electrodes. Moreover, the evaluation of the device used copper ions as the detection species. The current of the device that combined flow-through with quasi-steady flow was about twice as large as other schemes and owned higher sensitivity. This strategy provides new insights and a more facile way to amplify signals of ePADs.
Cheng Yuemeng,Feng Shaoqing,Ning Qihong,Li Tangan,Xu Hao,Sun Qingwen,Cui Daxiang,Wang Kan
In this research, we design and implement a small, convenient, and noninvasive paper-based microfluidic sweat sensor that can simultaneously detect multiple key biomarkers in human sweat. The origami structure of the chip includes colorimetric and electrochemical sensing regions. Different colorimetric sensing regions are modified with specific chromogenic reagents to selectively identify glucose, lactate, uric acid, and magnesium ions in sweat, as well as the pH value. The regions of electrochemical sensing detect cortisol in sweat by molecular imprinting. The entire chip is composed of hydrophilically and hydrophobically treated filter paper, and 3D microfluidic channels are constructed by using folding paper. The thread-based channels formed after the hydrophilic and hydrophobic modifications are used to control the rate of sweat flow, which in turn can be used to control the sequence of reactions in the differently developing colored regions to ensure that signals of the best color can be captured simultaneously by the colorimetric sensing regions. Finally, the results of on-body experiments verify the reliability of the proposed sweat sensor and its potential for the noninvasive identification of a variety of sweat biomarkers.
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