After surface modification, I would like to measure the contact angle of treated material, but the water droplet doesn't stick to the surface of the material. I tried a couple of times at different places on the surface, but it doesn't work. How can I handle this problem? And is there any different method or instrument to measure contact angle? Thanks in advance for your valuable comments and suggestions.
I have done water contact angle measurements of hydrophilic and super hydrophobic membranes. You must have done sessile drop static method. For me this method works very well. If it is not working well, you can try dynamic Wilhelmy method. In this method for calculating average advancing and receding contact angles on solids of uniform geometry. Both sides of the solid must have the same properties. Wetting force on the solid is measured as the solid is immersed in or withdrawn from a liquid of known surface tension. I use this method for the water contact angle measurements of hollow fibers.
http://www.sysmex.be/index.asp?id=11682
I haven't done any contact angle measurements myself, but contact angle can be measured by placing the material in a water bath and measuring the resulting meniscus using a tensiometer e.g. the capillary rise method. For example: http://www.attension.com/applications/measurements/contact-angle
http://www.sciencedirect.com/science/article/pii/S0927775712002634
but it depends on your substrate.
I have done water contact angle measurements of hydrophilic and super hydrophobic membranes. You must have done sessile drop static method. For me this method works very well. If it is not working well, you can try dynamic Wilhelmy method. In this method for calculating average advancing and receding contact angles on solids of uniform geometry. Both sides of the solid must have the same properties. Wetting force on the solid is measured as the solid is immersed in or withdrawn from a liquid of known surface tension. I use this method for the water contact angle measurements of hollow fibers.
http://www.sysmex.be/index.asp?id=11682
You might place a drop on the surface using a pipette, not a needle. Drop might be larger then. Then visually inspect the shape, afterwards tilt the surface. Does the drop run of? If yes, you have Cassie-Baxter wetting, if not, it's Wentzel wetting. You may find details in the www. Imaging with a high-speed cam during run-off would give you advancing and receeding contact angle.
I suggest you to read following paper:
Güler, T., Çetinkaya, S., Akdemir, Ü., Doğan, T., Kocabağ, D., 2009. Effect of Fe-ions on pyrite-xanthate interaction in chemically manipulated electrochemical conditions, International Journal of Natural and Engineering Sciences, V.3(3), pp.1-7.
Ozkan, in my opinion if you still wish to use water as liquid phase for contact angle try Advancing and Receding approach. In this your dispensing tip is kept in contact with water droplet. You could measure advancing angle by dispensing additional volume, e.g 0.5 ul and then receding same volume. As your surface seems superhydrophobic your advancing and receding angle should be close and give you estimate of your contact angle range.
All the best,
Deepesh
Ozkan, as Lijo Francis told, you must chose one of the Wielhelmy or Sessile methods but not using the pipette or needle. The best instrument that i know is { PGX+ Measuring Head } from Gardner company. however based on the surface specification you can use water or another solvent. I use this method for the water contact angle measurements of some modified surfaces.
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