Rapid fabrication of versatile omni-directional and long-distance three-dimensional flow paper-fluidic analytical devices using a cut-and-insert method for biomedical applications
Paper fluidics has recently offered an approach to precisely guide liquid flow in analytical devices with a low-cost regime. Multiple paper layers expand the capability of analytical devices to handle multiple samples as well as multiple detections simultaneously. Here we present a novel inexpensive cut-and-insert method to achieve a well-controlled even distribution of liquid in multi-channel three-dimensional (3D) paper-based analytical devices. A novel vacuum-driven poly dimethyl siloxane (PDMS) stamping method to pattern hydrophobic barriers in the filter paper enables rapid fabrication and assembly of microfluidic paper-based analytical devices (μ-PADs). The cut-and-insert assembly method facilitates more efficient fluid transfer than conventional O2 plasma-assisted overlapped channel binding, due to the strong physical contact between connected layers. The liquid transfer starts from the center region where two inserted layers are overlapped, and thus the presented method enables consistent liquid transfer independent of the angles of connected fluidic paths. Consequently, the angles between the connected μ-PAD strips as well as the 3D distance for the fluid transfer can be freely adjusted as needed. Also, multiple strips can be easily connected in series or in parallel. For example, perpendicularly connected bended paper channels guide upward and then lateral liquid flows by capillary action. Three important assays, i.e. nitrite 0 to 2 ppm, pH 1 to 10, and glucose 0 to 0.22 molL−1, were successfully implemented and measured simultaneously using a device with four strips connected in parallel.