Susanna Laurén Jun 11, ’19 < 3 min

How to measure contact angle hysteresis and roll-off angle by tilting method?

Contact angle hysteresis can give valuable information on the properties of your surfaces. One of the often-used measurement methods is called tilting cradle or plate. The droplet is placed on the sample after which the tilting of the sample is started. The measurement can be done either with the manual tilting stage where only the sample stage is tilted or with the automated tilting cradle where the whole instrument is tilted.

Automation for better repeatability and ease-of-use

The one benefit of automated tilting cradle is that the tilting can be done with constant inclination speed that is defined in the software. With the manual tilting stage, the speed of inclination is dependent on the user which can make it difficult to compare results between different users. With the automated method, the tilting angle is also recorded by the software which makes the determination of roll-off or sliding angle easier. Also, the placement of the drop is not that critical as the whole instrument is tilted. With the tilting stage, the drop needs to be placed on the center of the image  to ensure that the droplet is visible through the whole tilting range.

Volume of the drop influences the results

As the method is based on gravity, the volume of the droplet used is meaningful. The bigger the drop, the larger the gravity affected by the drop. It is thus important to use the same drop size if the results are being compared with each other. Typically, at least 10 µl drops are used. The roll-off or sliding angle is especially sensitive to the size of the droplet used.

To see how the measurements can be done in practice, please watch the video through the link below.

 Video   Contact angle hysteresis and roll-off angle with tilting method  Watch

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