Chinese researchers have developed a novel metal ink that can produce flexible electronic circuits on plain paper and other substrates, according to the American Chemical Society. The ink, made of copper nanosheets, might enable electronic books that resemble conventional ones as well as other flexible products, they hope. The team from Shejang Sci-Tech University, Hangzhou, China, and the University of Science and Technology Beijing, Beijing, China, put the ink in a pen and drew patterns of lines, words and even a flower on regular printer paper. They then studded the lines with LEDs and connected a battery to the circuit (see figure). In addition, they tested the ink’s flexibility by folding papers 1,000 times and even crumpling them — after which the ink still retained 80–90% of its conductivity, the researchers report.Details appear in “Synthesis and Self-Assembly of Large-Area Cu Nanosheets and Their Application as an Aqueous Conductive Ink on Flexible Electronics,” a paper recently published in ACS Applied Materials & Interfaces.