FIG. 2.

Emerging approaches to increase the packing density of paper-based assays. (a) Increasing the packing density using the origami technique. 3D origami-based devices, as a subset of 3D paper-based devices, are 3D multiple-layer products fabricated by folding patterned papers in the same footprint of a 2D device. (b) Increasing the packing density in 2D by raising patterning resolution to create more closely packed features. Having more control over the patterning resolution leads to the creation of hydrophobic boundaries with more detail, which can prevent diffusion of samples out of the channel or diffusion of patterning ink into the channel. Therefore, more channels with smaller size features and higher precision can be patterned, resulting in more complex, closely packed devices. (c) Increasing the packing density in 2D by shrinking via chemical post-treatment.