Spontaneous Oscillation Mechanism by Simultaneous Time-resolved Measurements of Interfacial Tensions of Both the Donor/Membrane and Membrane/Acceptor Phases

Quasi-elastic Laser Scattering for Measuring Inhomogeneous Interfacial Tension in Non-equilibrium Phenomena with Convective Flows

“…QELS method is based on the angle-and frequency-resolved detection of quasi-elastic light scattering by capillary waves at an interface, 4,5,[29][30][31][32][33][34][35][36][37][38] which is a kind of Brillouin scattering by ripplons. The capillary waves, which can have different frequencies, are generated by thermal fluctuations at the liquid surface or interface.…”

“…These techniques often perturb the effects that they seek to measure. Quasi-elastic laser scattering (QELS) 4,5,[29][30][31][32][33][34][35][36][37][38] method involves light scattering by capillary waves, and is one of the most useful tools for measuring interfacial tension in such non-equilibrium systems. This article describes the principle behind the QELS method, and reviews some applications of the method.…”

“…In the donor/membrane/ acceptor oscillator system, oscillations in the electric potential were in phase with those in tension at the membrane/acceptor interface, indicating that local adsorption of cetyltrimethylammonium bromide (CTAB) at membrane/ acceptor interface induces Marangoni convection, followed by their rapid adsorption. 35,37,38 The propagating chemical wave in an unstirred BZ reaction system showed an evolution in the interfacial tension, which was compared with the evolution of the ratio of concentrations of Fe(III) to Fe(II) in the spatiotemporal pattern of the bulk phase. 36 Finally, we investigated the propulsion mechanism of two different self-propelled objects: a camphor boat and an alcohol droplet floating on an aqueous phase.…”

Time-Resolved Measurements of Interfacial Tension and Flow Speed of the Inclined Water Surface around a Self-propelled Camphor Boat by the Quasi-elastic Laser Scattering Method

“…There are also techniques that observe the deformed shapes of liquids, such as the pendant drop method or oscillating-jet method, but they are also not suitable for in situ observations of the position-dependent interfacial tension. For in situ measurements of systems in motion, the authors have applied optical methods to observe the light scattering derived from capillary waves generated by thermal fluctuations of the interface. ,,− This method, called quasi-elastic laser scattering (QELS), enables not only noncontact and noninvasive measurement of the interfacial tension but also surface flow measurements . Hence, it is very suitable for the measurement of phenomena involving motions, and the authors so far have studied camphor boats, , self-propelled droplets, amoeba-like oil droplets, and oscillatory reactions. − , On the other hand, because the QELS method observes the Brillouin scattering by ripplons at a specific angle, the obtained signal has an inclination angle dependence of the interface, and artifacts sometimes appear when an interfacial deformation occurs in a simple measurement system.…”

“…37 Hence, it is very suitable for the measurement of phenomena involving motions, and the authors so far have studied camphor boats, 23,24 self-propelled droplets, 27 amoeba-like oil droplets, 36 and oscillatory reactions. [29][30][31]35 On the other hand, because the QELS method observes the Brillouin scattering by ripplons at a specific angle, the obtained signal has an inclination angle dependence of the interface, and artifacts sometimes appear when an interfacial deformation occurs in a simple measurement system. There is also a detection problem for the refracted referential local oscillator light especially when there is interfacial deformation.…”