Wet microelectronic technologies on paper substrate for flexible electronic applications

Flexible electronics on paper is currently a challenging area of research. The use of an economical and ecological substrate, such as paper, has significant potential compared to a plastic substrate, such as PET (Polyethylene Terephthalate) or Kapton® (Polyimide). However, the roughness and tearing of paper due to moisture and temperature during operation constitute major technical challenges, considering the potential application in electronics. The use of printing techniques, such as gravure, flexographic, screen, offset, inkjet, conductive and dielectric inks, and organic polymers, all of which have different viscosities suitable for machine deposition, may allow to electronic devices on a paper substrate; example products using this technology include flexible batteries, solar cell, displays, and biomedical devices. This technology only presents a small number of disadvantages, which include poor conductivity, expensive materials, and difficulties with subtractive batch processes, such as photolithography and vacuum processes. In this article, the authors chose an unconventional way to reduce the impact of these disadvantages by adapting technological processes of microelectronics (i.e., photolithography, metal vapour deposition, electroplating, and etching) for use on a standard paper substrate.