Method and device for measuring surface properties

A method of determining a reduced contact angle of liquid on a test article, the method comprising:

• positioning an imaging sensor at a known vantage point to a surface of a test article;
• depositing, with a liquid dispenser, a first liquid as liquid droplets along a trajectory toward the surface to form and to impact energy to a liquid drop, wherein each droplet imparts an amount of energy to the liquid drop to increase the volume of the drop having a drop perimeter, said energy being sufficient for the drop perimeter to expand beyond its equilibrium diameter for that volume;
• and
• after a time interval after a selected droplet for allowing the drop perimeter to retract as the excess energy is dissipated and the liquid drop to form a reduced contact angle with the surface, detecting via the imaging sensor a geometric characteristic of the liquid drop that is related to a reduced contact angle of the liquid drop to the surface;
• and
• determining with a data generator the reduced contact angle based at least in part upon the geometric characteristic.

A method for obtaining equilibrium contact angles of liquids on surfaces, the method comprising:

• depositing a liquid in a manner whereby the volume of the drop is increased through stepwise addition of smaller liquid volume elements,
• whereby each increment of volume growth causes the perimeter of the drop to advance across the surface,
• whereby the incremental liquid volume elements impart sufficient energy to expand a liquid drop perimeter of the growing drop beyond an equilibrium diameter for a volume of the growing drop, and
• whereby the drop perimeter will tend to contract between volume additions as the excess energy is dissipated;
• and
• determining the equilibrium contact angle between the incremental volume additions.