3D printing „inks“ can be erased selectively
One of the most important properties of 3D printing is that it allows complex geometries to be produced very efficiently. Direct laser writing is considered a particularly promising method: A computer-controlled focused laser beam functions as a pen and creates the desired structure in a photoresist. This makes it possible to produce three-dimensional structures with details in the sub-micrometer range. High resolution is particularly attractive for applications that require highly precise filigree structures, such as in biomedicine, microfluidics, microelectronics or optical metamaterials.
Researchers at the Karlsruhe Institute of Technology (KIT) had already succeeded in decisively expanding the possibilities of direct laser writing: The research groups of Professor Martin Wegener at the Institute of Applied Physics (APH) and the Institute of Nanotechnology (INT) at KIT and Professor Christopher Barner-Kowollik developed an erasable ink for 3D printing. The components of the ink can be separated from each other again thanks to a reversible bond.
Scientists at KIT Karlsruhe and Queensland University of Technology in Brisbane (Australia) have now significantly refined this feature. As they report in Nature Communications magazine, they have developed several inks, in different colours, so to speak, which can be erased independently of each other.
This makes it possible to selectively and sequentially degrade and rebuild the laser-written microstructures. For example, temporary supports can be erected for particularly complex constructions and removed again in the further construction process. In three-dimensional frameworks for cell growth, it may be possible to remove and add parts to observe how cells react to such changes. In addition, the selectively erasable 3-D inks allow the replacement of damaged or worn parts in complex constructions.
In the production of fissile photoresists, the researchers were inspired by degradable biomaterials: The photoresists are based on silane compounds that are easy to separate. Silanes are silicon-hydrogen compounds. The scientists prepared them for photoresists by targeted atomic exchange. In this way, microstructures can be broken down under mild conditions without damaging structures with different material properties – a major advantage over earlier erasable 3-D inks. The new photoresists also contain the monomer pentaerythritol triacrylate, which significantly improves the writing process without impairing erasability.
Original publication (Open Access): David Gräfe, Andreas Wickberg, Markus Michael Zieger, Martin Wegener, Eva Blasco & Christopher Barner-Kowollik: Adding chemically selective subtraction to multi-material 3D additive manufacturing. Nature Communications. 2018. DOI: 10,1038/s41467-018-05234-0