Direct 3D laser printing or laser writing uses a computer-controlled focused laser beam to generate the structures. The process produces micrometer-sized objects with defined properties. Researchers from the Karlsruhe Institute of Technology (KIT) have developed a method that actually erases the ink used for 3D printing, allowing the small structures up to 100 nm to be repeatedly erased and rewritten if need be. This new development opens up many new 3D fabrication applications. 3D microstructures can be written using a laser, erased, and rewritten. Courtesy of KIT. "Developing an ink that can be erased again was one of the big challenges in direct laser writing," said professor Christopher Barner-Kowollik of KIT's Institute for Chemical Technology and Polymer Chemistry. KIT researchers have successfully developed an ink with reversible bonding. The printed structure is simply erased by immersing it into a chemical solvent and can be rewritten or modified repeatedly. The process was developed in close cooperation with professor Martin Wegener's group at the Institute of Applied Physics and the Institute of Nanotechnology of KIT. The physicists developed highly specialized 3D printers that produce scaffolds up to 100 nm in size by direct laser writing. Structures written with erasable ink can be integrated into structures made of non-erasable ink. According to the scientists, it is also possible to produce reversible wire bonds from erasable conducting structures in the future. A permanent ink can be mixed with a nonpermanent ink to influence the properties of the printed material and make it more or less porous, for instance. "3D printing already is indispensable in many fabrication areas. Its importance is increasing,” said Barner-Kowollik . "According to estimations, some 10 percent of all goods will be produced by 3D printing in 2030.” The new process is presented in the journal Angewandte Chemie under the heading "Cleaving Direct Laser Written Microstructures on Demand" (doi: 10.1002/anie.201701593).