Mechanical Engineering Department-Microtech Lab., Universitat Politecnica de Catalunya, C/Colom 7-11, CP 08222 Terrassa, Spain.
Department of Mining, Industrial and ICT Engineering (EMIT), Universitat Politecnica de Catalunya, AV. Bases de Manresa 61-73, CP 08240 Manresa, Spain.
Sensors (Basel). 2021 May 11;21(10):3328. doi: 10.3390/s21103328.
Microfluidic paper-based analytical devices (µPADs) are a promising technology to enable accurate and quantitative in situ assays. Paper's inherent hydrophilicity drives the fluids without the need for external pressure sources. However, controlling the flow in the porous medium has remained a challenge. This study addresses this problem from the nature of the paper substrate and its design. A computational fluid dynamic model has been developed, which couples the characteristics of the porous media (fiber length, fiber diameter and porosity) to the fluidic performance of the diffusion-based µPAD sensor. The numerical results showed that for a given porous membrane, the diffusion, and therefore the sensor performance is affected not only by the substrate nature but also by the inlets' orientation. Given a porous substrate, the optimum performance is achieved by the lowest inlets' angle. A diffusion-based self-referencing colorimetric sensor was built and validated according to the design. The device is able to quantify the hydronium concentration in wines by comparison to 0.1-1.0 M tartaric acid solutions with a 41.3 mM limit of detection. This research showed that by proper adjustments even the simplest µPADs can be used in quantitative assays for agri-food applications.
微流控纸基分析器件（µPADs）是一种很有前途的技术，可以实现准确和定量的现场分析。纸的固有亲水性无需外部压力源即可驱动流体。然而，控制多孔介质中的流动仍然是一个挑战。本研究从纸基片的性质及其设计方面解决了这个问题。已经开发了一种计算流体动力学模型，该模型将多孔介质的特性（纤维长度、纤维直径和孔隙率）与基于扩散的µPAD 传感器的流体性能相结合。数值结果表明，对于给定的多孔膜，扩散，因此传感器的性能不仅受基底性质的影响，还受入口方向的影响。对于给定的多孔基底，通过最低的入口角度可以获得最佳性能。根据设计，构建并验证了基于扩散的自参考比色传感器。该装置能够通过与 0.1-1.0 M 酒石酸溶液的比较，定量检测葡萄酒中的氢离子浓度，检测限为 41.3 mM。这项研究表明，通过适当的调整，即使是最简单的 µPADs 也可以用于农业食品应用的定量分析。
