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Precisely controlling plastic particles: Bayreuth physicists find unusual colloids

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University of Bayreuth, Press release No. 029/2018, 27 February 2018

Physicists at the University of Bayreuth have discovered plastic particles that enable the movements of individual particles to be observed without interruption and to be precisely controlled. New microchips which are only a few tenths of a millimetre in size and which are capable of providing such control are thus no longer the stuff of science fiction. These plastic particles are colloids. In the interior of a complex magnetically structured material, they barely change their position at all, however at the edge of the material they move quite rapidly.


Following in the footsteps of Nobel laureates

The colloids thus behave similarly to the electrons of topological insulators, a material class that has fascinated physicists for the past couple of years. Topological insulators are characterized by their ability to conduct electrical current at the material periphery but prevent electrical current from entering their interior. It was British physicists David Thouless, Duncan Haldane, and Michael Kosterlitz who received the Nobel Prize in Physics in 2016 for the important contributions they made to the investigation of such solids by way of their theoretical calculations. Since then, there has been increased interest in large particles which have properties similar to those of the much smaller electrons in topological insulators and which are analogous to them.

The Bayreuth physicists have now succeeded in identifying such particles for the first time. They are colloids which keep their position when placed in the interior of a complex material. However, they are able to crawl along the edge of this material, where they move forward in a looping pattern. To date, no other particles are known to be similar to the electrons of topological insulators in this way.


Future chips as miniature laboratories

The unusual behaviour of these colloids in and on a complex material is due to the structured magnetic field to which they are exposed. As a result of this magnetic field, not only can the movement of the colloids be observed without interruption, they can also be precisely controlled.

In exactly this context, there is promising potential for future applications in research and development: “Individual molecules can be placed on the colloids, for example in the scope of biomedical examinations, and these individual molecules can be precisely transported from one position to a different target by “piggybaciking”. The colloids are thus well-suited for producing microchips on which these processes can be precisely controlled and observed. These chips would then be miniature laboratories for a diverse range of experiments that rely on this type of precise control,” explained Dr. Daniel de las Heras, who is carrying out the research in Bayreuth together with Dr. Johannes Löhr.

Research cooperation:

These findings that have now been published in Communications Physics stem from close cooperation with research groups at the University of Kassel and the Adam Mickiewicz University in Poznań.


Loehr, J., de las Heras, D., Jarosz, A., Urbaniak, M., Stobiecki, F., Tomita, A., Huhnstock, R., Koch, I., Ehresmann, A., Holzinger, D. & Fischer, Th. M., Colloidal topological insulators.
Communication Physics (2018), DOI: 10.1038/s42005-017-0004-1


Prof. Dr. Thomas Fischer
Experimental Physics V
University of Bayreuth
Phone: +49 (0)921 / 55-3342
E-mail: thomas.fischer@uni-bayreuth.de

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