Measuring interfacial tension using electrostatic oscillations
Inventors
NARAYANAN, RANGANATHAN • Ward, Kevin L.
Assignees
National Science Foundation NSF • University of Florida Research Foundation Inc
Publication Number
US-10641694-B2
Publication Date
2020-05-05
Expiration Date
2036-10-14
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Abstract
An exemplary embodiment of an interfacial tension measurement system of the present disclosure is one in which Faraday waves or instability are formed within a vessel of fluids to be tested via electrostatic oscillations. Then, by tracking the amplitude of an applied electrical voltage having an AC harmonic load to the mixture of fluids that result in a Faraday instability, as well as the wavelength of the instability, the interfacial tension measurement system determines the interfacial tension between layers of immiscible liquids present in the vessel.
Core Innovation
The invention relates to an interfacial tension measurement system and method that uses electrostatic oscillations to form Faraday waves or instability within a vessel containing immiscible liquids. By applying an AC harmonic voltage load across electrodes positioned at the top and bottom of the vessel, vertical oscillations in the liquids are induced. The system tracks the amplitude of this applied voltage and the wavelength of the resulting Faraday instability to determine the interfacial tension between the liquid layers.
The system includes a vessel holding two or more immiscible liquids, with electrodes arranged above and below the vessel. A voltage source provides an AC harmonic load at a fixed frequency, creating electrostatic oscillations that force a Faraday instability at the liquid interface. A camera captures images of this instability to determine its wavelength, and a controller increases the voltage amplitude until the onset of the instability is detected. The interfacial tension is then calculated based on the critical amplitude, wavelength, and frequency of the applied voltage using a theoretical relationship.
The problem addressed is the inability of existing technologies to measure interfacial tension under certain conditions, particularly for samples with high melting points, high viscosities, or similar densities, and in extreme environments. Conventional devices such as drop tension meters, spinning drop tension meters, and Wilhelmy plate meters are limited and not easily used in such conditions, especially for liquids like high melting point liquid metals. This invention solves these limitations by employing electrostatic oscillations and Faraday instabilities to accurately measure interfacial tension without such constraints.
Claims Coverage
The patent includes two independent claims that cover a system and a method for measuring interfacial tension using electrostatic oscillations and Faraday instability detection.
System for measuring interfacial tension using electrostatic oscillations and Faraday instability detection
The system comprises a vessel holding multiple immiscible liquids, with a first electrode at the vessel's top and a second electrode at the bottom. A voltage source is connected between the electrodes to supply an AC harmonic load at a fixed frequency, creating electrostatic oscillations within the liquids. A camera positioned above the vessel captures images of a Faraday instability at the interface, including pattern shape indicating wavelength. A controller increases the AC load amplitude, detects the amplitude at onset of the instability, and determines the interfacial tension based on the amplitude, wavelength, and fixed frequency.
Method for measuring interfacial tension via electrostatic oscillations and Faraday instability
The method involves passing an electrostatic oscillation at a fixed frequency vertically through a vessel holding multiple immiscible liquids and increasing its amplitude until a Faraday instability onset occurs. It records the critical amplitude and wavelength of the instability, determines the interfacial tension based on these values and frequency, and outputs the measurement. It includes capturing images to detect the instability, changing frequency to repeat measurements, graphically plotting critical amplitudes across frequencies, and comparing experimental plots to theoretical plots to select the correct interfacial tension.
The inventive features focus on applying and controlling electrostatic oscillations between electrodes in a vessel to induce and detect Faraday instabilities at liquid interfaces, using captured data and theoretical models to accurately measure interfacial tension, both as a system and as a method.
Stated Advantages
The system and method can measure interfacial tension in samples with high melting points, high viscosities, or similar densities which were previously untestable by conventional devices.
The measurement technique allows use in extreme environments, such as high temperature chambers, without loss of accuracy.
The method provides highly accurate interfacial tension measurements validated by close matching of experimental data to theoretical models.
Documented Applications
Processes involving low interfacial tension fluids, such as in the cosmetic industry.
Production and growth processes of semiconductor crystals where knowledge of interfacial tension between melt and encapsulant is needed to control conditions in a furnace atmosphere.
Use in high temperature or extreme environment chambers where conventional tension meters are ineffective.
Testing of liquids with high melting points, high viscosities, or similar densities, thereby broadening fluids that can be measured.
Application in conjunction with levitation experiments for other thermophysical property measurements.
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