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Static measurements yield values in-between the advancing and receding contact angle depending on deposition parameters (e.g. velocity, angle, and drop size) and drop history (e.g. evaporation from time of deposition). Contact angle hysteresis is defined as θ A – θ R although the term is also used to describe the expression cos θ R – cos ...
As with the tilt method, the difference between the advancing and receding contact angles is the contact angle hysteresis. Most researchers prefer the tilt method; the add/remove method requires that a tip or needle stay embedded in the drop which can affect the accuracy of the values, especially the receding contact angle.
A contact angle less than 90° (low contact angle) usually indicates that wetting of the surface is very favorable, and the fluid will spread over a large area of the surface. Contact angles greater than 90° (high contact angle) generally mean that wetting of the surface is unfavorable, so the fluid will minimize contact with the surface and ...
Contact angle is a measure of static hydrophobicity, and contact angle hysteresis and slide angle are dynamic measures. Contact angle hysteresis is a phenomenon that characterizes surface heterogeneity. [15] When a pipette injects a liquid onto a solid, the liquid will form some contact angle.
Contact angle is a measure of static hydrophobicity, and contact angle hysteresis and slide angle are dynamic measures. Contact angle hysteresis is a phenomenon that characterizes surface heterogeneity. [16] When a pipette injects a liquid onto a solid, the liquid will form some contact angle.
An ideal solid surface is flat, rigid, perfectly smooth, and chemically homogeneous, and has zero contact angle hysteresis. Zero hysteresis implies the advancing and receding contact angles are equal. Figure 1: Contact angle for a liquid droplet on a solid surface. In other words, only one thermodynamically stable contact angle exists. When a ...
A low contact angle indicates a high solid surface energy or chemical affinity, and a high or sometimes complete degree of wetting. For example, a contact angle of zero degrees will occur when the droplet has turned into a flat puddle; this is called complete wetting .
Figure 3: Figure demonstrating the meaning of contact angle inside a capillary as well as the radius of curvature for a meniscus. Contact angle , or wetting angle , is a very important parameter in real systems where perfect wetting ( θ {\displaystyle \ \theta } = 0 o ) is hardly ever achieved.