A broad overview on innovative functionalized paper solutions

Abstract Functionalized paper solutions have attracted the attention of many research groups in the 21st century, given the low cost, availability, flexibility and biodegradability of paper. Despite this material has been manufactured for more than two thousand years, its traditional uses hardly go beyond writing, printing, cleaning and packaging. This overview covers fascinating advances in the functionalization of paper that have taken place this century. This century, test strips for glucose and pH have evolved towards microfluidic paper analytical devices that allow for accurate quantitative determinations. In another context, paper electronics started with the first paper-based transistors and followed with more sophisticated electronic devices. Also, cheap paper-based membranes and adsorbents have been proposed for water treatment, and researchers have found innovative ways to confer antimicrobial and anti-counterfeiting properties to paper. Furthermore, numberless ways to functionalize paper are reported here. Fibers can be modified by chemical reactions, nanofibrillation or supramolecular interactions with certain reagents. The surface can be coated by diverse methods, including size press coating, sputtering, e-beam evaporation and the sol-gel process. Special inks can be printed onto paper to make hydrophobic, conductive or luminescent patterns. Brief opinions about future outlooks are given at the end.