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Austrian Science News: Quantum physicist Zeilinger elected to National Academy of Sciences | 3D Printing | Dental Fillings

The Austrian quantum physicist Anton Zeilinger was recently officially named to be a foreign associate of the National Academy of Sciences (NAS) in the USA. Zeilinger, Professor at the Institute for Quantum Optics and Quantum Information at the University of Vienna, has served as President of the Austrian Academy of Sciences since 2013, and has also been a member of the French Academy of Sciences since then.

Zeilinger

Anton Zeilinger or “Mr. Beam“. Photo: J. Godany

“Mr. Beam”, “Quantum Pope”, “Pop Star of Natural Sciences“, “Witch Master from Vienna“ are also names given to Anton Zeilinger, whose graying and bushy beard and curly hair seem to perfectly fit the cliche of a scientist, enjoys immense popularity in spite of the complicated nature of his work. Once the “Zeit” said this can be mainly attributed to the fact that Zeilinger “can convey his enthusiasm because he himself is so excited about what he does”.

Zeilinger became particularly well-known due to his experiments in the field of quantum teleportation. In addition, he is working on applications for quantum physics, especially in new fields related to quantum information and quantum cryptography. However, his primary interest is in the fundamental principles underlying quantum physics and their implications for our everyday understanding based on our experiences. In 1997 Zeilinger and his working group succeeded for the first time to demonstrate the quantum teleportation of the state of an independent photon.

3D NANOPRINTER – SMALLER THAN ALLOWED BY LIGHT?

The victorious expansion of nanotechnology has transformed computers from room-filling devices weighing tons to light smart phones which are millions of times more powerful. This has been made possible by the incredibly precise manufacturing methods which frequently make use of strongly focused lasers.

A 3D nanoprinter was enormously improved at Johannes Kepler University in Linz. Austria. The biggest challenge in the process is the bundle the capabilities of the laser strongly enough.

Impressive hair splitting

In the process of two photon lithography, a gentle infrared laser is focused on a liquid photoresist which is hardened by the chemical reaction. In order to produce the desired amount of nanostructure, the focus is moved through the material like a stylus, similar to a 3D printer. In this case, the line thickness is only one five hundredth of a hair’s breadth.

Another laser, whose beam circularly envelopes the excitation laser, prevents hardening at the edge by means of stimulated emissions. “This enables smaller line widths, enabling me to outsmart the diffraction limit”, explains Richard Wollhofen from the Institute for Applied Physics. He succeeded in creating polymer lines featuring only seven percent of the width of the excitation wavelength, a process which is already being applied. One can attach and precisely pinpoint antibodies on the surfaces of glass with his polymers, and thus to systematically examine and better understand our immune system.

 

PHOTOACTIVE MOLECULES USED IN DENTAL FILLINGS

A new dental filling material has been developed at the Vienna University of Technology which allows light to penetrate more deeply and thus the filling hardens in only half the number of working steps.

Dental fillings commonly make use of white composite materials which can hardly be distinguished visually from the tooth. These materials are hardened with light. However, the light cannot penetrate into the material as deeply as desired. Up until now these fillings have been applied and hardened in several steps. The Vienna University of Technology and the company Ivoclar Vivadent have jointly developed a germanium-based compound which considerably simplifies this process.

Hardening with light

Modern dental composites consist of a mixture of different material components. In addition to inorganic fillers they usually contain molecules which react to light of a particular wavelength and solidify relatively quickly if irradiated with a special lamp.

Professor Robert Liska and his team at the Vienna University of Technology (TU Vienna) have been working for a long time with such photoactive substances i.e. substances which react to light. Similar photoactive substances are used for additional applications including 3D printing processes.

The penetration depth of the light in the dental filling material depends, among other factors, on its wavelength. “Usually, light in the violet and ultraviolet region is used”, says Robert Liska. There are alternatives which use light with longer wavelengths. This goes deeper into the material, but then the process is less efficient in triggering the necessary chemical reaction.  If the light does not penetrate deep enough into the material in order to harden the filling in one step, the procedure has to be repeated several times. If the cavity is large, this can last uncomfortably long.

Germanium compound triggers chain reactions

This problem can now be solved with a new Germanium-based compound. It only makes up 0.03% of the composite material, but it plays a crucial role. The molecule is split into two parts by blue light, creating radicals, which in turn initiate a chain reaction. The molecular compounds which are already present in the filling assemble into polymers, and the material hardens. Using this new compound, the hardening depth could be increased from 2 mm to 4 mm, which considerably reduces the duration of the medical procedure.