Contact Angle and Surface Tension Determination Service

Advanced characterization of wetting using a goniometer to determine the contact angle of liquid droplets deposited on a surface is a quantitative and non-destructive analysis technique in general, depending on the surface reactivity with the wetting liquid. The combination of several liquids allows to determine the surface tension of the wet solid and to estimate the work of adhesion in simulated environments. The control of the wettability of smart surfaces under the action of external stimuli such as the application of light, temperature and/or humidity gradients, changes in pH or electric fields, are of great interest in advanced applications for the aeronautical industry, lines of communication, transportation, protection, heritage, solar and wind energy or biomedicine, among others.

Determination of the contact angle is carried out by applying Young’s equation for interfacial tension balance, with sensitivity at the nanometric scale. The tests can be carried out in static or in dynamic modes to obtain hysteresis (advanced and receding angle values) of surfaces and critical values ​​of droplet sliding. Regarding the surface tension of the solid surface, implemented theoretical models are those of Owens, Wendt, Rabel and Kaelble, Extended Fowkes, Schultz and Van Oss&Good and Neumann, based on the existence of polar and dispersive components. In addition, the temporal tracking of the surface contact angle accounts for aging and stability in certain environments. Finally, the assistance of a controlled temperature and humidity chamber allows studies of condensation/evaporation and freezing/thawing of water on surfaces.

The contact angle and surface tension measurement equipment has been supported by the Junta de Andalucía (Aid for R&D infrastructure and equipment 2019-PAIDI2020 European Regional Development Fund)

Available Equipment

DataPhysics OCA 25 Optical Contact Angle Goniometer, consisting of::

• double injection system with liquid drop volume, between nanoliters (close to the state of the art) to tens of microliters, controlled by a magnetic valve for dispensing
• TBU100 tilting platform for studies of droplet sliding on the surface (-5º – 95º)
• sample holder base adjustable in 3 spatial directions
• TPC160 thermoelectric module for temperature control (from -30ºC to 150ºC)
• module for the application of electric field EWP100 in studies of wetting electrostimulation (0-64kV DC/AC, 3-10mm electrode distance)
• HGC30 electro-humidification chamber to control the humidity of the environment (from 5% to 90%)
• SCA 21 software with routine for surface tension estimation (0.01-2000 mN/m)
• front (3250 f/s) and vertical (2450 f/s) optical systems