Method and device for measuring minute volume of liquid

A liquid dispensing apparatus calibration system comprising:

• a calibrating reference surface that is previously tested with a test volume of liquid imparted with a test amount of kinetic energy that defines a deposition condition to determine a characteristic contact angle of the calibrating reference surface;
• a liquid dispensing apparatus that that dispenses a drop of the liquid, having an assumed volume to be measured, in a non-perpendicular trajectory that separates from the liquid dispensing apparatus prior to being deposited onto the calibrating reference surface the test amount of kinetic energy that is substantially the same as the deposition condition;
• and
• a testing apparatus for intermittent confirmation and adjustment of the liquid dispensing apparatus, the testing apparatus comprising:
• a dimension determining component that determines one or more dimensions of the liquid drop deposited on the calibrating reference surface;
• and
• a processor component communicatively coupled to the dimension determining component and which:
• determines an assumed volume to be dispensed by a liquid dispensing apparatus based on pressurizing a liquid to a defined pressure that is dispensed by controlling a nozzle valve orifice to open for a defined interval of time to dispense a droplet having kinetic energy comprising a velocity related to flow rate of the liquid;
• determines the known characteristic contact angle for the calibrating reference surface based at least in part on the velocity of the liquid drop;
• determines an actual calculated volume of the drop of liquid based on the one or more dimensions of the drop of liquid and the known characteristic contact angle;
• determines the difference between the assumed volume and the calculated actual volume of the drop of liquid;
• and
• adjusts the liquid dispensing apparatus to correct for the difference between the calculated actual volume and the assumed volume for a subsequently dispensed drop of liquid.

A method of determining a volume of a droplet of liquid dispensed from a liquid dispensing apparatus, the method comprising:

• determining an assumed volume to be dispensed by a liquid dispensing apparatus based on pressurizing a liquid to a defined pressure that is dispensed by controlling a nozzle valve orifice to open for a defined interval of time to dispense a droplet having kinetic energy comprising a velocity of the drop related to flow rate of the liquid;
• depositing an assumed volume of liquid to be measured from the liquid dispensing apparatus as a drop that separates from the liquid dispensing apparatus prior to being deposited onto a calibrating reference surface, wherein the calibrating reference surface provides for a known contact angle with the drop of liquid under the deposition conditions used comprising the velocity of the drop that is non-perpendicular to the calibrating surface;
• establishing a known contact angle with the drop of liquid selected from the group consisting of:
• (i) an advancing contact angle, (ii) a receding contact angle, and (iii) an intermediate contact angle;
• measuring a dimension of the drop of liquid, wherein the dimension measured is selected from the group consisting of (i) a maximum height of the drop, (ii) a diameter of the contact patch, (iii) radius of curvature, and (iv) cross sectional area;
• and
• calculating the actual volume of the drop of liquid from the relationship of the known contact angle to the measured dimension, wherein (i) an advancing contact angle, (ii) a receding contact angle, and (iii) an intermediate contact angle are established by varying the kinetic energy imparted to the deposited liquid drop.