A novel patterning method for three-dimensional paper-based devices by using inkjet-printed water mask

Paper-based devices are continuing to grow rapidly. However, conventional paper patterning methods are mostly restricted to the fabrication of two-dimensional (2D) patterns. Here, we present a novel patterning method for the fabrication of 2D and 3D paper-based devices. For the first time, a 3D fluidic channel network with multiple crossings of fluidic channels is successfully fabricated on a layer of paper without sophisticated procedures. The proposed method utilizes a commercially available inkjet printer to print water pattern as a protective mask onto both sides of a paper substrate and followed by soaking the sample into a non-polar solution which contains a hydrophobic substance to form hydrophobic barriers on the paper substrate. The printed water mask helps preventing the adsorption of the non-polar solution into the printed water area resulting in the formation of hydrophobic and hydrophilic areas. This opens up a new route towards the development of 2D and 3D paper-based devices using low-cost equipment and a variety of materials.