March 14, 2012

Vienna University Sets New Speed Record for 3D-Nanoprinting

Austrian researchers have claimed the world speed record for the fastest 3D-nanoprint of objects smaller than a grain of sand.

The team was able to produce a scale model of a Formula-1 racecar one-hundredth-of-an-inch in length in just over four minutes. The car was produced in about 100 layers, each consisting of about 200 single printed lines.

The researchers at the Vienna University of Technology (TU Vienna) said their technique is far faster than similar devices out there. They said it opens the door for completely new areas of application, such as medicine. They said the technique could also be used to make small biomechanical parts.

“The technology itself is quite well known in the science arena, but the problem was that it was always extremely slow,” Professor Jurgen Stampfl, the lead researcher of project, told the BBC. “It was good as a showcase, but for real world applications it was much too time-consuming. Making complex large 3D structures would take hours or even days.”

“Using our set-up and materials, we can speed that up by a factor of 500 or in some cases 1,000 times,” he said.

The creation was produced using “two-photon lithography.” It involves focusing a laser beam onto liquid resin to harden it, leaving behind a line of solid polymer just a few nanometers wide. Unlike traditional 3D-printing techniques which build up an object by adding layers to its surface, the laser can create solid material anywhere within the liquid material.

The process gets its name because the resin only sets if the molecules within it absorb two photons of the laser beam at once -- which only occurs at the center of the beam.

Jan Torgersen, co-researcher of the project at TU Vienna, said this amazing progress was made possible by combining several new ideas. “It was crucial to improve the control mechanism of the mirrors,” which are constantly in motion during the printing process, Torgersen said. The acceleration and deceleration-periods have to be tuned very precisely to achieve high-resolution results at a record-breaking speed.

Torgersen noted that 3D-printing isn´t just about mechanics --chemistry played a crucial role in the project as well.

“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,” he said.

Professor Robert Liska at TU Vienna, worked with a team of chemists to develop the suitable initiators for the special resin used in the 3D nanoprinting.

“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,” Stampfl emphasized. 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 speed, Stampfl said much larger objects can now be created in a given period of time. This makes two-photon lithography an interesting technique for industry.

The researchers are now developing bio-compatible resins so that the objects they create can potentially be used in the medical field. One suggested application is to create scaffolds which cells could use to build new biological tissues.

Engineers at Washington State University have already shown that 3D-printers can be used to create scaffolds to promote the re-growth of damaged bone.

Stampfl said because his team´s technique can work in water-based environments it is also capable of creating scaffolds suitable for softer tissues such as cartilage and muscle tissue.

“We can also ℠write´ these structures in the presence of cells as we use an infrared laser which is completely harmless for biological tissue,” he added. “This is not possible with other 3D-printing techniques which first rely on making the scaffolds and then seed the cells, or use a thin inkjet nozzle to push through the cells which may damage them.”

“The two-photon lithography technique lets us do the writing in the same space as the cells - what we call in-vivo writing.”


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