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SVT – Spinning drop video tensiometer

The spinning drop video tensiometers of the SVT series are special-purpose optical instruments for measuring extremely low interfacial tensions and rheological properties. This measuring technique offers unrivalled possibilities for the analysis of surfactant effectiveness in the development of emulsions or in the enhanced oil recovery. In the following you will learn about the possibilities that the spinning drop tensiometry offers and about our SVT models with their accessories and intuitive software control.

SVT 20N brochurefile_download

Spinning Drop Tensiometry

Spinning drop tensiometry is the technology of choice for measuring extremely small interfacial tensions. The method is based on the optical contour analysis of a drop. This drop, instead of hanging from a dosing needle and being exposed to gravitation, is located inside of a rotating capillary.

Inside of the capillary the centrifugal force pushes the denser liquid surrounding the drop outwards while the less dense drop gets pushed towards the rotational axis. Hence the drop is deformed cylindrically and its interfacial area increases. The interfacial tension counteracts this area increase and thus can be determined by analysing the equilibrium drop shape.

Vonnegut evaluation

An easy and established evaluation method for strongly elongated drops is the interfacial tension calculation by Vonnegut. Here the shape that the drop adopts at rotation with the angular velocity ω is approximated by a cylinder. The cylinder has a rotational energy that decreases with decreasing radius, which compensates the increase in interfacial energy due to increasing elongation and interfacial area. In the equilibrium state an energy minimum is reached. Vonnegut equation:

Vonnegut equation

Drop deformation with the spinning drop principle

Enhanced oil recovery (EOR)

Ultra-low interfacial tensions occur particularly in microemulsions which are used, for example, in enhanced oil recovery. At suitable conditions microemulsions form spontaneously from water, oil and surfactant. Hence the oil can be extracted from the reservoir as part of the thermodynamically stable microemulsion system. Interfacial tension measurements by spinning drop tensiometry are an essential tool in the research of appropriate surfactants and mixture compositions.

Oil pump

Interfacial rheology

With spinning drop tensiometry it is also possible to analyse how an interface reacts when its area is enlarged or reduced (interfacial rheology). For example, how fast can surfactants from the bulk adsorb at the interface in order to stabilise a newly formed emulsion? To investigate such questions the rotational velocity is varied in a spinning drop experiment, typically in an oscillating manner, which directly results in a change of size of the interfacial area.

Spinning drop

The SVT models

The Spinning drop video tensiometers of the SVT series are compact optical measuring instruments for the determination of low to ultra-low interfacial tensions and rheological interface properties. Powerful device components like automated camera positioning, a precision drive and temperature-controlled measuring chambers guarantee accurate and reproducible measurement results. Convenient fast-exchange capillaries and an intuitive control ensure flexible sample handling and easy operation.

For an efficient measuring procedure the measuring cell, with the rotating capillary, is mounted on a tilting table, which allows the operator to easily move the drop of interest into the camera view. Once detected the drop is automatically tracked by the movable camera. A highly dynamic measurement drive creates a uniform rotation even at highest rotational velocities. In addition it allows for sinusoidal changes in revolution speed for oscillation measurements and for rapid rotational velocity steps.

Samples can be easily placed inside the SVT, within seconds, due to fast-exchange capillaries with perfect fitting accuracy. Hence the highest throughput rates can be assured. In order to avoid extensive cleaning procedures disposable glass tubes with corresponding holders can also be used for the measurement.

Temperatures within the range of -30 °C to 180 °C can be reached inside the SVT measuring chambers. This facilitates the recreation of many different environmental conditions. It is even possible to investigate the interfacial behaviour of aqueous samples at temperatures above 100 °C due to a special design of the capillaries.

SVT 20N

SVT 15N

The SVT 15N is the entry-level spinning drop tensiometer, for measuring ultra-low interfacial tensions. With its precision drive capillaries can be rotated at up to 17000 rev/min.

Main features

  • high-performance 6-fold zoom with integrated continuous fine focus and adjustable observation angle
  • video measuring system (max. 123 frames/s)
  • precise, fast and easy to use capillary exchange system
  • measuring cell with automatic, software controlled position and tilt adjustment
  • LED lighting with software controlled adjustable intensity
  • automatic calibration function for correcting optical distortions caused by the capillaries (cylindrical lens effects
  • precision drive with 0 … 17000 rev/min

Software

The SVTSoftware is available in various independently usable modules. The available software modules for the SVT 15N are:

Learn more about the SVTS modules.

Accessories

Due to the modular product design the SVT 15N can be combined with a multitude of options of the versatile SVT accessories range. Learn more about the available accessories.

SVT 15N brochurefile_download

SVT 15N

SVT 20N

The SVT 20N is the high performance spinning drop tensiometer, for measuring ultra-low interfacial tensions and for investigating interfacial rheology. With its high performance precision drive capillaries can be rotated at up to 20000 rev/min and oscillations of the rotational speed can be realised. With its integrated touch screen the SVT 20N can be controlled intuitively.

Main features

  • high-performance 6-fold zoom with integrated continuous fine focus and adjustable observation angle
  • video measuring system (max. 123 frames/s)
  • precise, fast and easy to use capillary exchange system
  • measuring cell with automatic, software controlled position and tilt adjustment
  • stroboscopic and permanent LED-lighting with software controlled intensity and strobe frequency
  • automatic calibration function for correcting optical distortions caused by the capillaries (cylindrical lens effects
  • high performance precision drive with 0 … 20000 rev/min
  • oscillation measurements with oscillation period of 0.5 s …∞ and a max. acceleration of 500 rev/s2
  • integrated touch screen for intuitive control

Software

The SVTSoftware is available in various independently usable modules. The available software modules for the SVT 20N are:

Learn more about the SVTS modules.

Accessories

Due to the modular product design the SVT 20N can be combined with a multitude of options of the versatile SVT accessories range. Learn more about the available accessories.

SVT 20N brochurefile_download

SVT 20N