Flow Control-based 3D μPADs for Organophosphate Pesticide Detection

Flow control-based paper devices have recently shown great potential for point-of-need analysis, since they allow for the easy operation of multi-step assays by minimizing user operation. In this work, a wax printing method was evaluated as a means to control liquid flow in 3D microfluidic paper-based analytical devices (mu PADs). The resulting flow control based 3D mu PADs were applied to determine paraoxon-ethyl as a typical organophosphate pesticide model system. The analytical procedure is as simple as applying a 200-mu L sample solution, resulting in reproducible (relative standard deviation of colorimetric signals from 6 independently fabricated devices, 2.63%) colorimetric signals within 1 h of the assay time with the limit of detection (LOD) reaching 25.0 mu g/L. Finally, results obtained for pesticide-spiked water samples analyzed by flow control-based 3D mu PADs showed good agreement with those from a conventional HPLC analysis with UV detection.