Patterning and Modeling Three-Dimensional Microfluidic Devices Fabricated on a Single Sheet of Paper

This work describes a method to fabricate three-dimensional paper microfluidic devices in one step, without the need of stacking layers of paper, glue, or tape. We used a nontransparent negative photoresist that allows patterning selectively (vertically) the paper, creating systems of two or three layers, including channels. To demonstrate the capabilities of this methodology, we designed, fabricated, and tested a six-level diluter. The performance of the device was also simulated using a simple numerical model implemented in the program PETSc-FEM. The resulting μPAD is small (1.6 cm × 2.2 cm), inexpensive, requires low volumes of sample (5 μL), and is able to perform mixing and dilution in 2 min.