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Tuesday, March 13, 2012

Ultra-high-resolution 3D Printer Breaks Speed-Records at Vienna University of Technology

By Nick Flaherty 
A 285 µm racecar, printed at the Vienna University of Technology
A 285 µm racecar, printed at the Vienna University of Technology

The London Tower Bridge
The London Tower Bridge (credit: Klaus Cicha) The distance between the towers is 90µm 
Researchers at the Vienna University of Technology (TU Vienna) have made a major breakthrough in speeding up 3D printing at micron resolutions, opening up completely new areas of application, such as in medicine.
The 3D printer uses a liquid resin, which is hardened at precisely the correct spots by a focused laser beam. The focal point of the laser beam is guided through the resin by movable mirrors and leaves behind a polymerized line of solid polymer, just a few hundred nanometers wide. This high resolution enables the creation of intricately structured sculptures as tiny as a grain of sand. “Until now, this technique used to be quite slow”, said Professor Jürgen Stampfl from the Institute of Materials Science and Technology at the TU Vienna. “The printing speed used to be measured in millimeters per second – our device can do five meters in one second.” This was possible by combining several new ideas, from the laser control to the resin.
“It was crucial to improve the control mechanism of the mirrors”, said researcher Jan Torgersen. The mirrors are continuously in motion during the printing process. The acceleration and deceleration-periods have to be tuned very precisely to achieve high-resolution results at a record-breaking speed.
“The resin contains molecules, which are activated by the laser light. They induce a chain reaction in other components of the resin, so-called monomers, and turn them into a solid”, said Torgersen. These initiator molecules are only activated if they absorb two photons of the laser beam at once – and this only happens in the very center of the laser beam, where the intensity is highest. In contrast to conventional 3D-printing techniques, solid material can be created anywhere within the liquid resin rather than on top of the previously created layer only. Therefore, the working surface does not have to be specially prepared before the next layer can be produced, saving a lot of time. A team of chemists led by Professor Robert Liska at TU Vienna developed the suitable initiators for this special resin. 
Because of the dramatically increased speed, much larger objects can now be created in a given period of time. This makes two-photon-lithography an interesting technique for industry. At the TU Vienna, scientists are now developing bio-compatible resins for medical applications. They can be used to create scaffolds to which living cells can attach themselves facilitating the systematic creation of biological tissues. The 3D printer could also be used to create tailor made construction parts for biomedical technology or nanotechnology.

The video shows the 3d-printing process in real time. Due to the very fast guiding of the laser beam, 100 layers, consisting of approximately 200 single lines each, are produced in four minutes.

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