Fabrication of Three-dimensional Microfluidic Channels in a Single Layer of Cellulose Paper

This paper reports a novel technique for fabricating three-dimensional (3D) microfluidic channels in a single sheet of paper, which greatly simplifies the fabrication process of 3D microfluidic paper-based analytical devices (3D-μPADs). This technique, derived from the popular wax printing technique for paper channel patterning, is capable of controlling the penetration depth of wax upon heating, which is printed on both sides of a paper substrate, and thus forming multilayers of patterned channel in the substrate (up to four layers of channels were fabricated in a 315 μm thick paper sheet). Heating time and density of printed wax (i.e., grayscale level for wax printing) were used as parameters to control the penetration depth of melted wax. This technique holds a great potential to further popularize the use of 3D-μPADs and enhance the mass-production quality of these devices.