Speaker: Péter Salamon (Wigner RCP)
Title: Interfacial instabilities and piezoelectricity in ferroelectric nematic fluids
Date: Tuesday, February 25, 2025, 10:00
Place: Building 1, Conference room
Abstract:
The ferroelectric nematic liquid crystal phase is a recently discovered new state of matter, which exhibits spontaneous electric polarization while being a low viscosity fluid. I will present that the free surface of such ferroelectric fluids becomes unstable in electric fields and shows various instabilities depending on the magnitude and frequency of the applied voltage. All instabilities are characterized by sharp threshold voltages. First, a fractal-like spiky growth of the fluid interface called ramification can be observed [1]. The secondary instability results in a labyrinth-like liquid structure, which has an analogy in magnetic ferrofluids exposed to magnetic field [2]. At even higher voltages in a specific frequency range the ferroelectric droplets move as active interacting particles resembling living organisms like swarming insects, microbes or microrobots [3]. The motion is accompanied by sound emission, as a consequence of piezoelectricity and electrostriction. I present the first demonstration of converse piezoelectricity in 3D fluids by measuring a linear electromechanical effect in ferroelectric nematic liquid crystals [4]. The observed piezoelectric coupling constant is larger than 1 nC/N, comparable to solid piezoelectric materials. Understanding the electromechanical response of ferroelectric nematics will enable mechanical energy harvesting and open up a new avenue for developing fluid actuators, micro positioners, and electrically tunable optical lenses. Furthermore, I will present that the extraordinary electric properties of ferroelectric nematics can not only destabilize the fluid surface but can stabilize as well so that the fluid can overtake the limitation of the Plateau–Rayleigh instability and form long slender fibers [5].
[1] M.T. Máthé et al., Scientific Reports 13, 6981 (2023)
[2] M.T. Máthé et al., Journal of Molecular Liquids 413, 126047 (2024)
[3] M.T. Máthé et al., Nature Communications 15, 6928 (2024)
[4] M.T. Máthé et al., Advanced Functional Materials 18, 2314158 (2024)
[5] M.T. Máthé et al., Advanced Science 11, 2305950 (2024)
2025. február 25. kedd, 10.00
Wigner FK SZFI, 1. ép. 1. em. nagy előadóterem
