Stadler, Dominik and Hofmann, Matthias J. and Motschmann, Hubert and Shamonin, Mikhail (2016) Automated system for measuring the surface dilational modulus of liquid-air interfaces. MEASUREMENT SCIENCE AND TECHNOLOGY, 27 (6): 065301. ISSN 0957-0233, 1361-6501
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The surface dilational modulus is a crucial parameter for describing the rheological properties of aqueous surfactant solutions. These properties are important for many technological processes. The present paper describes a fully automated instrument based on the oscillating bubble technique. It works in the frequency range from 1 Hz to 500 Hz, where surfactant exchange dynamics governs the relaxation process. The originality of instrument design is the consistent combination of modern measurement technologies with advanced imaging and signal processing algorithms. Key steps on the way to reliable and precise measurements are the excitation of harmonic oscillation of the bubble, phase sensitive evaluation of the pressure response, adjustment and maintenance of the bubble shape to half sphere geometry for compensation of thermal drifts, contour tracing of the bubbles video images, removal of noise and artefacts within the image for improving the reliability of the measurement, and, in particular, a complex trigger scheme for the measurement of the oscillation amplitude, which may vary with frequency as a result of resonances. The corresponding automation and programming tasks are described in detail. Various programming strategies, such as the use of MATLAB (R) software and native C++ code are discussed. An advance in the measurement technique is demonstrated by a fully automated measurement. The instrument has the potential to mature into a standard technique in the fields of colloid and interface chemistry and provides a significant extension of the frequency range to established competing techniques and state-of-the-art devices based on the same measurement principle.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | OSCILLATING BUBBLE TECHNIQUE; MEDIUM FREQUENCY-RANGE; DILATATIONAL PROPERTIES; STABILITY; TENSIOMETRY; RHEOLOGY; surface rheology; dilational modulus; automated measurements; image processing; signal processing; graphical user interfaces; oscillating bubble technique |
| Subjects: | 500 Science > 540 Chemistry & allied sciences |
| Divisions: | Chemistry and Pharmacy > Institut für Physikalische und Theoretische Chemie > Chair of Chemistry VI - Physical Chemistry (Solution Chemistry) > Prof. Dr. Hubert Motschmann |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 25 Mar 2019 13:58 |
| Last Modified: | 25 Mar 2019 13:58 |
| URI: | https://pred.uni-regensburg.de/id/eprint/2899 |
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