Wettability is commonly measured with contact angle using optical tensiometers. The drop is placed on the sample surface and an image of the drop is taken. The image is then analyzed by the software, most typically using Young-Laplace fitting. The Common drop size for contact angle measurement is between one to 10 microliters. However, in some cases, the area available for the measurement is limited. In these cases, smaller drop volumes are needed.
There are several applications where wettability needs to be measured on small areas such as on PCB boards or small medical devices. The size of the measurement area determines what size of the drops should be used.
When using a picoliter dispenser for contact angle measurement, the nozzle size as well as the contact angle affects how wide the drop is on the sample surface. With picoliter dispensers areas of as small as 100 um in width can be measured.
However, there are several applications where the area is not as small, and more economic solutions could be used. With Attension disposable tip dispenser, it’s possible to measure surface areas down to 0,5 mm in diameter. A positive displacement accessory is needed to enable the measurement. The drop is created at the tip of the needle and brought in contact with the sample surface. The volume and width of the drop depend on the size of the initial drop on the needle, the speed of deposition, and the wettability of the surface.
Susanna is an Application Scientist at Biolin Scientific. In her PhD thesis, she developed fabrication methods for a new type of inorganic-organic polymers. Microfabricated polymer chips were utilized as tool for biomolecule separation in analytical chemistry.
