should I be getting the same contact angles for the same 1 µL drop volume on the different parts of a smooth horizontal glass plate surface ? how much deviation/varaition in the contact angles should be acceptable ?
I am using the Sessile droplet method so that I can place exactly 1 µL drop every time on the glass plate surface.
The contact angle should always be the same for the same surface, same liquid volume, and same liquid. If there is a variation of more than a couple of °, you should question whether your surface or your liquid is sufficiently homogeneous or your analysis is done properly.
The contact angle of the drop depends on the surface roughness.
Initially the contact angle solely depends on the three phases present (liquid, substrate, and surrounding fluid.) and not on the volume. However, assuming your surface to be real, contact angle depends on present imperfections.
By infusing/retracting fluid in/from the droplet you should measure a hysteresis between a so-called advancing and receding contact angles. The difference being proportional to the surface roughness.
When depositing a drop on a surface the (static) contact angle should be comprised between this two values. You should be able then to determine the error on your measurement.
Methodologies are available in the literature and from contact angle measurement devices manuals to do this estimation.
- Badges
- Science topic
- Similar topics
- Engineering
- Thermal Engineering
- Thermofluid
- Fluid Mechanics