Contact angle hysteresis mechanism

With 7 = 0.072 Nm-1 and 5 = 10 nm the effective pressure is of the order of P = 72 x 10s Pa. Such a high pressure can change the surface structure, cause mechanical deformation at the moving wetting line [250], and can lead to contact angle hysteresis [251-253], especially on soft polymer surfaces. 

Regarding the mechanism, of capillary condensation, it is possible that more than one is viable, depending on the nature of the pores. As long ago as 1911 Zslgmundi J recognized the phenomenon he attributed it to contact angle hysteresis. 

Chen, Y. L., Helm, C. A., and Israelachvili, J. N. Molecular mechanisms associated w ith adhesion and contact angle hysteresis of monolayer surfaces. ]. Phys. Chem., 95, 10736 (1991). 

The non-slip boundary condition is discussed in an excellent paper by Huh and Scriven They take note of the fact that, previous workers seem not to have been well informed by fluid mechanics , in aUuding to the essentially surface chemical analyses of spreading dynamics. Another point they address is that except for very smooth surfaces and non-adsorbing hquids the advancing or receding of the contact line proceeds in a slip-stick and discontinuous fashion a fact which is the focus of attention in current analyses of contact angle hysteresis using the theory of random fluctuations... 

Our steering results are demonstrated using an experimentally validated numerical model [20] of droplet motion inside the UCLA electrowetting system [21, 22], This model of EWOD fluid dynamics includes surface tensimi and electrowetting interface forces, viscous low Reynolds two-phase fluid flow, and the essential loss mechanisms due to contact angle saturatimi, triple point line pinning, and the related mechanism of contact angle hysteresis. 

Contact angle hysteresis can be attributed to a departure from the conditions of ideality of the solid, namely, surface roughness, chemical inhomogeneities, or contamination, or the presence of solute (polymers or surfactants) deposits on the surface [2]. Figure 7 shows a plan view illustration of the hysteresis mechanism in which the receding contact line of a drop is locally pinned when the drop moves over a localized surface inheterogeneity which is more hydrophilic than... 

A-PEO-A V-PDMS-V Cohydrosilylation Sol fraction, DS in hexane and water, contact angle hysteresis, oxygen permeability, TGA, mechanical properties 86... 

Contact angle hysteresis is one mechanism that hinders motion of fluid drops in a porous medium. Find an expression for the pressure drop... 

Some theoretical studies have investigated the structure of the mechanical energy functional of ideal three-phase systems on surfaces with ordered patterns of wettability. ° Energy barriers in that functional arise from the heterogeneity of the surface and trap the contact line in metastable positions. This gives rise to contact angle hysteresis. 

Chen YL, Helm CA, IsiaelachviUe JN (1991) Molecular mechanisms associated with adhesion and contact angle hysteresis of monolayer siutfaces. J Phys Chem 95 10736-10747... 

Effect of phase state of monolayers of hexadecylsiloxane supported on oxidized PDMS-hysteresis in interfacial energetics as determined by contact mechanics and contact angles... 

H, particularly when contact angles are in the range of intermediate wettability. Consequently, each mechanism should be expected to play a role in GDM capillary behavior. For instance, the attribution of capillary pressure hysteresis entirely to hysteresis of the contact angle in the sense of Eq. (3)59 can be correct only if GDMs are composed of bundles of tubes of cylindrical cross section.60... 

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