National Physical Laboratory

Sessile Drop

The sessile drop technique is a flexible video system for measuring contact angle, surface and interfacial tensions, wettability, and absorption. The instrument uses a micro-pipette mounted in an arm to dispense a liquid over the measurement location. The pipette will handle drop volumes from 3 to 10 µl with 0.1 µl resolution. The action appears live on the computer screen and the salient images are captured to the computer's memory for later image analysis. The time scale can vary from 1/60 second (60 images/second) to hours and can be varied nonlinearly to efficiently follow absorptions. The system can capture both static and dynamic behavior of liquid interactions.

Measurements for surface tension, contact angles, surface energy and adhesion characteristics can be carried using this technique. The instrument uses the 'drop shape' analysis technique. It captures video images of liquid droplets to analyse their shape and size to determine various surface chemistry quantities.

NPL has carried out research in comparison of various surface characterisation techniques as part of the research programmes.

Related publications

Determining the wettability of substrates to hot melt adhesives Adobe Acrobat PDF file

Techniques for characterising the wetting, coating and spreading of adhesive surfaces Adobe Acrobat PDF file

Last Updated: 10 Aug 2010
Created: 10 Aug 2010


Please note that the information will not be divulged to third parties, or used without your permission