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‘World beating’ 3D printer enables nano-precision

14 Mar 2012

Researchers at Vienna University of Technology have significantly speeded up a two-photon solid prototyping technique.

Printing three dimensional objects with incredibly fine details is now possible using “two-photon lithography”. With this technology, tiny structures on a nanometer scale can be fabricated.

Researchers at the Vienna University of Technology (TU Vienna) have made a breakthrough in speeding up this printing technique: Their high-precision-3D-printer is claimed to be orders of magnitude faster than similar devices, as this video shows.

The scientists say that this achievement enables new application areas, 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 hardened 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”, says Professor Jürgen Stampfl from the Institute of Materials Science and Technology at the TU Vienna. “The typical printing speed used to be measured in millimeters per second – but now our device can print five meters in one second.”

In two-photon lithography, this is a world record achievement.

Jan Torgersen, also working at the TU Vienna, continues, “This amazing progress was made possible by combining several new ideas. It was crucial to improve the steering mechanism of the mirrors.”

The mirrors are continuously in motion during the printing process. The acceleration and deceleration-periods have to be tuned precisely to achieve high-resolution results at the record-breaking speed.

Photoactive molecules harden resin

Torgersen adds that 3D-printing is not all about mechanics: “Chemists had a crucial role to play in this project too. The resin contains molecules that are activated by the laser light, which induce a chain reaction in other components of the resin, the monomers, and turn them into a solid.”

These initiator molecules are only activated if they absorb precisely two photons of the laser beam at once – and this only happens in the center of the laser beam, where the intensity is highest.

In contrast to conventional 3D-printing techniques, in the new TUV process, solid material can be created anywhere within the liquid resin rather than only on top of the previously created layer. Therefore, the working surface does not have to be specially prepared before the next layer can be produced, which saves time.

A team of chemists led by Professor Robert Liska (also based at the TU Vienna) developed the formula of this special resin. 
Researchers worldwide are working on 3D printers today – both at universities and in industry.

Jürgen Stampfl concluded: “Our competitive edge here at the Vienna University of Technology comes from the fact that we have experts from very different fields, working on different parts of the problem, at one single university. In materials science, process engineering or the optimization of light sources, there are experts working together and coming up with mutually stimulating ideas.”

Because of the dramatically increased prototyping speed, much larger objects can now be created in a given period of time. This should make two-photon-lithography a more interesting technique for industry.

At the TU Vienna, scientists are now developing bio-compatible resins for medical applications. These 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.

About the Author

Matthew Peach is a contributing editor to optics.org

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