How to fix a droplet size for various surface characteristics in the process of measuring the Contact Angles? Especially for superhydrophobic surfaces.
Dear Bruce,
As far as I know there is not an exact value for the droplet volume. Usually, researches have presented experiments using volumes varying between 1uL to about 10 uL. Frequently, it is around 4-6 uL. There is an influence of both the droplet volume and the distance from the target surface in which the droplet is released. It will usually affect the initial contact angle. Thus, your measures should last time enough for a contact angle stabilization. What you can try is to test at least two to three different droplet volumes and see if the contact angle varies significantly or not.
I hope it can help you in your experiments.
Best regards
Dear Bruce Ralphin Rose
Although your question is not clear to me. I guess you would like to measure the CA for various surfaces and you would like to know what droplet volume should be used?
For any hydrophilic and hydrophobic surfaces, you can use any volume lesser than a critical volume (restricted by the Bond number to get rid of the effect of the gravity). But, I know dispensing smaller volumes over a superhydrophobic substrates would be challenging.
But with my experiences, you still can dispense any volume lesser than 3 uL.
Hope my answer serves your query.
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