Interest in dynamic wetting processes has immensely increased during the last ten years. In many industrial and medical applications, some strategies to control drop spreading on solid surfaces are being developed. One possibility is that a surfactant is added to a liquid.
Dynamic wetting measurements are carried out with a FibroDAT 1122 dynamic absorption and contact angle tester from Fibro Systems Sweden / Reppalon GmbH Suisse equipped with a high speed video camera which allows to collect up to 1000 images per second. The device has some advantages over other contact angle measuring systems, which are especially important for performing the dynamic wetting measurements with aqueous surfactant solutions:
- adjustment of specified (small) drop volumes using a liquid delivery system;
- tuning the deposition parameters such as the distance between a drop and a solid surface, the time difference between drop formation on the syringe tip and drop deposition on the surface, as well as the intensity of a very short stroke from an electromagnet to release the drop from the tip;
- checking the surface tension of surfactant solutions before wetting measurements
With a DAT 1129 Tilt Table it is possible to determine ‘wetting hysteresis’ characterized by the advancing/receding contact angles as a function of tilt angle. The tilt angle, at which the drops slides, is reported together with the advancing/receding contact angles.
Samples under study: polymer films, paper sheets, metal foils, textile materials
To attain a better understanding of processes during spreading, surfactant adsorption are being studied by time-resolved ellipsometry
Dr. habil. R. Miller, Max Planck Institute for Colloid and Interfacial Research Potsdam/Golm, Germany
Prof. Dr. B. Radoev, Institute of Physical Chemistry, University of Sofia, Bulgaria
Prof. Dr. V. Starov, Department of Chemical Engineering, University of Loughborough, United Kingdom