Contact angle Cassie-Baxter

The second set of equations come from Cassie and Baxter - l. Cassle eonsidered a smooth, but chemically patchwlse heterogeneous solid surface, composed of fractions and with ideeil contact angles and a, respectively. For the average he wrote the Cassie equatiorfi ... 

In 1944, Cassie and Baxter derived an equation describing contact angle hysteresis for composite smooth solid surfaces with varying degrees of heterogeneity ... 

When air pockets are present on a rough surface, the Cassie-Baxter equation can also be applied to the contact angle estimate of a water drop on such a surface. Since the contact angle of water in air is equal to 180°, by taking 02 = 180°, which corresponds to (cos ft = -1), Equation (676) then becomes... 

The modified Cassie-Baxter equation was successfully used to interpret some of the contact angle data reported for heterogeneous surfaces. 

The effect of roughness on the wettability of an idealized sinusoidal surface has been studied with a digital computer. The equations of Wenzel and of Cassie and Baxter are discussed in relation to the model. The heights of the energy barriers between metastable states of a drop are seen to be of utmost importance in determining the magnitude of contact angle hysteresis. 

Maximum and minimum possible angles Most probable contact angles, 0 Lower. Calculated from Wenzel s equation Upper. Calculated from Cassie and Baxter s equation Possible curve of receding angles Possible curve of advancing angles... 

Fig. 6. Effect of roughness on contact angle A, maximum and minimum angle B, Wenzel equation (lower) and Cassie and Baxter equation (upper) 6, and 6 possible receding and advancing angles (Ref. )...

Fig. 9. Effect of surface chemical heterogeneity (0, = 120°, 0j = 0°) on contact angle hysteresis A, Cassie and Baxter angle, curves 1-4 represent effect of assumed energy barriers (Ref.

A treatment similar to Wenzel s has been given by Cassie and Baxter [69] for chemically heterogeneous surfaces. For the case of a surface consisting of two types of patches, for which the intrinsic contact angles are 0] and 02, respectively, minimization of the system free energy leads to the Cassie-Baxter equation ... 

Wetting, Lotus effect, super-hydrophobicity, water repellence, contact angle, Wenzel equation, Cassie-Baxter equation, roU-off angle... 

The earliest theoretical work to model the apparent contact angle of drops on rough surfaces can be attributed to Wenzel [13] and Cassie and Baxter [14]. Wenzel... 

---