There is no such thing as “surface tension of solid surface”. Surface Tension is for a pair of surfaces. You need an interface between two surfaces to define a. However, quite often, the surface energy is determined using the contact angle measurement. In such a case, the surface tension of the liquid used enters into. A recently developed, Gibbsian-based correlation between interfacial tensions and individual surface tensions was used to calculate the.
Illustration of capillary rise and contact angle in a capillery. Measuring methods Many measuring methods have been described in the literature but only a few of them have been found to be widely applicable.
The Sessile Drop Method The most frequently used is the goniometer-telescope measurement of sessile-drop contact angles. Commercial contact angle goniometers employ a microscope objective to view the angle directly.
In the static method a drop is deposited on a surface and the contact angle can be measured by looking at the drop through a goniometer an instrument that measures contact angles.
The dynamic method is similar to the static one but the drop of liquid which is deposited on a surface is modified. Volume is then removed to produce the smallest possible angle, which is called the receding angle.
Contact Angles - Chemistry LibreTexts
The difference between those two measured angles is called contact angle hysteresis. The contact angle is obtained directly form the height trough: It was discovered however that dynamic advancing contact angle is generally larger than the static one, even for a total wetting liquid and as a result this method can be erroneous.
Seibold et al, suggested a way to overcome this problem. It was observed that this constant term varies as a function of the liquid used, in contradiction with the Washburn approach which uses Hexane as a completely wetting liquid in order to find the radius of the pores.
The intercept at zero velocity gives the value of r. This finding was transformed into a method to calculate or measure the contact angle at zero velocity.
Applications The interest in contact angles is because it plays a significant role in a number of technological, environmental and biological phenomena.
Water imbibition into porous media theory has been shown to have a multidisciplinary validity in food, soil physics, geology, printings and more. Imbibition of a liquid by a porous solid is a phenomenon highly dependent on wetting.
Capillary imbibition is a mechanism that plays a significant role during rehydration of dry food particles that are considered as porous media. Older systems used a microscope optical system with a back light.
Current-generation systems employ high resolution cameras and software to capture and analyze the contact angle. Angles measured in such a way are often quite close to advancing contact angles. Equilibrium contact angles can be obtained through the application of well defined vibrations.
Surface tension and contact angle
This complexity is further amplified when one attempts to incline the surface. Experimental apparatus to measure pendant drop contact angles on inclined substrates has been developed recently. An automated system allows for tilting the substrate and analysing the images for the calculation of advancing and receding contact angles. The dynamic sessile drop method[ edit ] Main article: Sessile drop technique The dynamic sessile drop is similar to the static sessile drop but requires the drop to be modified.
A common type of dynamic sessile drop study determines the largest contact angle possible without increasing its solid—liquid interfacial area by adding volume dynamically.
This maximum angle is the advancing angle. Volume is removed to produce the smallest possible angle, the receding angle. The difference between the advancing and receding angle is the contact angle hysteresis.