Hi, recently I am focusing on developing a new way to measure the size of drops adhered to solid. So I need to create different sizes of drops at first, and the more uniform the drops, the better.
Is there anyone that has some knowledge about this?
What is the desired size range for the drops? You should be able to produce pL to uL droplets with a piezoelectric droplet generator. You should be able to find many references for this. Here is an old school, simple, cheap single channel generator paper. http://www.nist.gov/el/fire_research/upload/Yang-A-Simple-Piezoelectric-Droplet-Generator.pdf
Thank you so much, I will see the paper. The desired size range is actually the wider the better, I will check whether the new method is available to all the size range I can get.
If I understand your question correctly, a straightforward way to create an array of water drops with different sizes would be to pattern a surface with alternating circular hydrophobic/hydrophillic regions of different diameters (hydrophillic where you want the drops). SiO2 on a silicon wafer would work fine.Pooling water on the top and then slowly tilting to remove excess water would leave the drop pattern you need (on the hydrophillic regions).
Though the diameter of the drops would be a known quantity (based on the size of the patterned features), the volume for a given diameter would have to be characterized (though probably just once) or inferred from knowledge of the different surface energies.
Try making surfaces vwith different surface roughness or pertubrabces
Eppendorf makes a product that can be used for this called the Femtojet. Depending on your level of funding and how much of an investment you want to make in this because it is relatively expensive. Here is a paper that details that method: http://scitation.aip.org/content/aip/journal/apl/98/9/10.1063/1.3560453