(170e) Effect of Interfacial Energy and Geometry to Permeation of Liquid through Filter Pores

The permeation of liquids through filter pores is studied as a function of contact angle of liquid and pore geometry. While it is generally known that the increased wettability, thus lower contact angles, increases the permeability, the quantification of its effect on permeability lacks. In addition, the effect of the shape/geometry of the pores on the permeation is not investigated. Yet, the geometry, especially the angle of the pore wall would also control permeability because it would change the radius of curvature of the menisci that would form inside the pores. This causes the difference in Laplace pressure and the different areas for a liquid to wet. Therefore, the dependence on permeability as a function of contact angle and pore geometry is studied.

To do so, an equation was developed that enables the calculation of the pressure for a liquid species, i, to permeate through a pore with the wall angle at α_j and the contact angle of the species i on the filter material, θ_i.

To verify the effect from the contact angle of a species through pores, θ_i, a cylindrical hole was prepared using a 3D printer, after which it was coated with PDMS to decrease the roughness. The contact angle of water on PDMS was altered by exposing the pore to UV-ozone. A glass tube was placed upon the pore and water was added gradually to observe the height at which the liquid started to permeate. The results that related the height to permeate as a function of θ_i was found to have the same functional form as the equation developed. To investigate the effect of α_j, tapered holes with various α_j were printed and used without further altering the contact angle of water (θ_water = 61°). It is observed that the decrease in the angle increased the height to permeate.