Wetting and Adhesion Force Measurements

To gain a better understanding of what contact angles are measuring, Samuel, Zhao, and Law [26] measured the wetting (attractive) and adhesion force between water and surface 1-20 directly using a microbalance inside a tensiometer. A schematic of the measurement procedure is shown in Fig. 5.4, and details of the instrumentation 

Briefly, a 5 mg water droplet was first deposited onto a platinum ring, which is attached to a microbalance. The surface of interest is placed on a stage where it can move up and down steadily at a slow rate (10 pm/s) by a computer-controlled stepping motor. Prior to the measurement, the microbalance is set to zero. When the water drop first touches the surface (Fig. 5.4 step b), an attractive snap-in force 

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