A research team at the HUN-REN Wigner Research Centre for Physics has identified a novel state of matter where liquid droplets, subjected to an electric field, exhibit active motion and interact like particles. This breakthrough has the potential to reshape applications in microfluidics, medical diagnostics, and biotechnology, the HUN-REN Hungarian Research Network announced on Monday.
Physicists Péter Salamon and Marcell Tibor Máthé focused their research on ferroelectric nematic liquid crystals, a recently discovered category of fluids. Their experiments revealed that when exposed to an electric field, the surface of these liquid droplets became unstable, forming fractal-like extensions.
At higher voltages, the droplets displayed even more extreme behaviour, losing their original shape and evolving into intricate, labyrinth-like structures. The researchers also observed that when an alternating current was applied within a specific frequency range, the droplets changed shape and began moving, repelling one another in a manner akin to swarming insects, microorganisms, or microrobots.
Crucially, the scientists demonstrated that they could control the movement of these droplets through voltage adjustments. This finding suggests promising applications in microfluidic devices, which are instrumental in medical diagnostics, chemical analysis, and biotechnological innovations.
Another surprising phenomenon noted during the study was that the droplets emitted sound as they moved. Spectral analysis of these emissions indicated that the alternating current induced mechanical vibrations in the liquid structures.
The research findings, published in Nature Communications, were part of a broader study in collaboration with Kent State University in the United States, led by Professor Antal Jákli. This partnership resulted in the first-ever identification of inverse piezoelectricity in three-dimensional liquids.
The inverse piezoelectric effect means that when a voltage is applied to a ferroelectric nematic liquid, it undergoes mechanical displacement proportional to the voltage. Conversely, mechanical deformation of the material generates electric charges on its surface.
Understanding the electromechanical response of ferroelectric nematic liquid crystals opens up new possibilities for harvesting mechanical energy. These discoveries could lead to the development of advanced liquid-based actuators, micropositioning systems, and electrically tunable optical lenses, marking a significant step forward in material science and engineering.
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