Minute micromotor is controlled directly by light


Researchers from the Faculty of Physics at Warsaw University and colleagues from Poland and China used liquid crystal elastomer technology to demonstrate a light-driven rotating micromotor. The ring with a diameter of 5 millimetres, which is driven and controlled by a laser beam, can rotate and perform work by turning, for example, another element installed on the same axis.

Rotational movements are very rare in nature, while at the same time they are omnipresent in our civilisation. Although we can build a variety of rotary motors, they are usually made up of many elements, which makes them difficult to miniaturize. However, there is one group of materials that allow the construction of small, mobile and/or portable devices – Liquid Crystal Elastomers (LCE). Research on these materials is mainly focused on the design of the LCE shape and its modification during laser illumination (e.g. shrinking, bending).

Liquid crystal elastomers are smart materials that can exhibit macroscopic, fast, reversible shape changes under various stimuli, including visible light illumination. They can be manufactured in various shapes on the micro and millimeter scale and can perform complex actuation tasks using molecular orientation technology.

Researchers from the University of Warsaw, together with colleagues from the Faculty of Mathematical Sciences at Xi’an Jiaotong Liverpool University in Suzhou, China, the Institute of Applied Physics at the Warsaw Armed Forces Technical University and the Centre for Polymer and Carbon Materials at the Polish Academy of Sciences in Zabrze, Poland, have now developed a micromotor that rotates thanks to the wandering deformation of the soft material caused by the laser beam and its interaction with the ground. The main part – the rotor – is a 5-millimeter ring. A suitable design of the alignment of the elastomer molecules ensures a stable performance of the micromotor or can increase the speed of rotation.

Film of the micromotor with 5.5 mm diameter, driven by a rotating laser beam. Credit: UW physics, Mikolaj Rogoz

Despite the low speed, about one revolution per minute, our motor allows us to look at the micromechanics of intelligent soft materials from a different perspective and gives us food for thought for their possible use, says Dr. Klaudia Dradrach from the Photonic Nanostructure Facility.

The motor design was inspired by piezoelectric ring motors, which are often found in the autofocus mechanisms of photographic lenses. The contribution of scientists from the Polish Academy of Sciences in Zabrze and the Military Technical University was crucial for the development of the method for reproducible production of LCE miniature components. Especially young researchers participated in the study, including Mikolaj Rogoz and Przemyslaw Grabowski, PhD students of the Faculty of Physics at the University of Warsaw.

The researchers, who previously demonstrated a light-driven screw robot that moves like its natural relatives, believe that new intelligent materials combined with advanced manufacturing methods will enable them to build more miniature components and drives.

Research on soft microrobots and polymer actuators is funded by the National Science Centre (Poland) as part of the “Microscale Actuators Based on Photoreactive Polymers” project, by the Polish Ministry of Science and Higher Education with a “Diamentowy Grant” for M. Rogoz, Ministry of National Defence (Poland), and with funds from Xi’an Jiaotong-Liverpool University.

Physics and astronomy were first published in 1816 at the University of Warsaw, at the then Faculty of Philosophy. In 1825 the Astronomical Observatory was founded. At present, the Faculty of Physics includes the Institutes of Experimental Physics, Theoretical Physics, Geophysics, Department of Mathematical Methods and an Astronomical Observatory. Research covers almost all areas of modern physics, on scales from quantum to cosmological. The research and teaching staff of the faculty consists of about 200 university professors, 78 of whom have a professorial title.


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