ELFT HÍRADÓ

[Szeminárium koordinátor <sem-admin AT szfki.hu>]

SZFI SeminarSalamon PéterHUN-REN Wigner RCP SZFIInterfacial instabilities and 
piezoelectricity in ferroelectric nematic fluidsTuesday, 25 February 2025, 
10:00, KFKI Campus, Bldg. 1, 2nd floor, Conference RoomThe 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) Minden érdeklődőt szívesen látunk! - Everyone is welcome 
to attend.Attila Nagysem-admin AT szfki.hu