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Cloth, treated to be hydrophobic, shows a high contact angle. The theoretical description of contact angle arises from the consideration of a thermodynamic equilibrium between the three phases: the liquid phase (L), the solid phase (S), and the gas or vapor phase (G) (which could be a mixture of ambient atmosphere and an equilibrium concentration of the liquid vapor).
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 ...
The captive bubble method is a method for measuring the contact angle between a liquid and a solid, by using drop shape analysis. [1] In this method, a bubble of air is injected beneath a solid, the surface of which is located in the liquid, instead of placing a drop on the solid as in the case of the sessile drop technique.
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.
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. [17] When a pipette injects a liquid onto a solid, the liquid will form some contact angle.
If water has a contact angle between < <, then the surface is classed as hydrophilic, whereas a surface producing a contact angle between < < is hydrophobic. In the special cases where the Contact angle is 150 ∘ < θ {\displaystyle 150^{\circ }<\theta } , then it is known as superhydrophobic.
Liquids 1 and 2 fully wet the surface as shown by their low contact angles, so they should be neglected when first drawing the line of best fit to find the critical liquid surface tension needed to effectively wet the PC surface, γ C, which is simply the x-intercept of the best fit line for the Zisman Plot.
A University of Nebraska-Lincoln team recently devised a computational approach that can relate the molecular hydrophobicity scale of amino-acid chains to the contact angle of water nanodroplet. [39] The team constructed planar networks composed of unified amino-acid side chains with native structure of the beta-sheet protein.