Fabrication of fully enclosed paper microfluidic devices using plasma deposition and etching

A fully enclosed paper microfluidic device has been fabricated using pentafluoroethane (PFE) plasma deposition followed by O₂ plasma etching. Structures with one and two non-interacting, fully enclosed hydrophilic channels were generated in a single paper sheet using metal masks. Furthermore, by performing an additional O₂ plasma step with a secondary mask, pinholes were created at the reaction zones for reagent loading. Finally, to demonstrate the functionality of the device, a glucose assay was performed. Quantitative analysis of glucose assays showed that the device can be used for the clinically relevant range of glucose. To our knowledge, this is the first time that such structures have been fabricated without paper stacking. Multi-layer devices have enhanced functionality relative to a single channel device, because the design space for creating networks of channels within the paper substrate is greatly expanded. The fluid-filled channels in the fabricated device are isolated, thereby preventing contamination due to handling and environmental exposure. Fluid evaporation can be inhibited by sealing the device with adhesive tape without contaminating the enclosed channels. The method described is a dry process and compatible with roll-to-roll technology, thus facilitating large scale production. The novel method to fabricate enclosed μ-PADs overcomes many of the limitations experienced with current approaches and thus offers an alternative means to develop low-cost point-of-care diagnostics for resource-limited settings.