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Surface roughness has a strong effect on the contact angle and wettability of a surface. The effect of roughness depends on if the droplet will wet the surface grooves or if air pockets will be left between the droplet and the surface. [10] If the surface is wetted homogeneously, the droplet is in Wenzel state. [11]
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 ...
Wettability is a measure of how well a liquid spreads and how complete the contact of the liquid is across the surface of a solid interface. A small contact angle indicates good wettability, while a large contact angle indicates poor wettability. The critical surface tension is the highest liquid surface tension that can completely wet a ...
Contact angles are important as they quantify a surface's wettability, the nature of solid-fluid intermolecular interactions. [2] Cassie's law is reserved for when a liquid completely covers both smooth and rough heterogeneous surfaces.
The most common way to measure surface energy is through contact angle experiments. [1] In this method, the contact angle of the surface is measured with several liquids, usually water and diiodomethane. Based on the contact angle results and knowing the surface tension of the liquids, the surface energy can be calculated. In practice, this ...
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 ...
The simplest way of measuring the contact angle of a sessile drop is with a contact angle goniometer, which allows the user to measure the contact angle visually. A droplet is deposited by a syringe which is positioned above the sample surface, and a high resolution camera captures the image from the profile or side view.
Washburn's equation is also used commonly to determine the contact angle of a liquid to a powder using a force tensiometer. [ 5 ] In the case of porous materials, many issues have been raised both about the physical meaning of the calculated pore radius r {\displaystyle r} [ 6 ] and the real possibility to use this equation for the calculation ...