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Drop and bubble analyzer:

The BubbleDrop Analyzer is a powerful surface analytical tool for Colloid-and Interface Science. It is the first commercial implementation of the oscillating bubble technique that allows the measurement of the complex surface dilational modulus E of aqueous surfactant systems up to 1000 Hz.

The module E is a fundamental system parameter which plays a crucial role in foaming, coatings, flotation, emulsions, or in the field of microfluidics. The extension of the frequency range is the decisive new element introduced by BubbleDrop Analyzer. Competing technology such as the oscillating drop technique is limited to an upper limit of about 1 Hz for fundamental reasons. The BubbleDrop Analyzer gives access to the high frequency limit of the module. The oscillating bubble technique has the potential to be accepted as a new standard technique in Colloid and interface Science.

The oscillating bubble technique allows the determination of the surface dilational viscoelastic properties of an adsorption layer at the liquid-air and liquid-liquid interfaces. The technique has been developed at the Max-Planck Institute of Colloid and Interfaces. The principle of the oscillating bubble technique is sketched in the following Figure showing a cross sectional view of the chamber.

A small hemispherical bubble is formed at the tip of a capillary with a radius of about 0.2 mm. The bubble is forced in a sinusoidal oscillation by a piezoelectric translator which is directly immersed in the liquid. As a result, a harmonic modulation of the pressure in the chamber is observed and recorded by a sensitive pressure transducer located at the bottom of the chamber. The amplitude of the pressure response and the phase-shift between piezo oscillation and pressure signal are evaluated via a phase sensitive lock-in detection scheme. The amplitude of the pressure response is proportional to the magnitude of the complex surface dilational module E, while the phase-shift yields the imaginary part of the modulus, in other words the surface dilational viscosity.

The implemented design give access to the frequency range of 1-1000 Hz and allows the determination the real- and imaginary part of the complex surface dilatational elasticity module

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