Surface Energy Study of UV-Curable Patterned Surface Involved Nano Silica Treated with Perflourosilane

Wettability of a surface are characterized by the static contact angle, made between a water droplet and surface. A surface is hydrophilic if the contact angle is less than 90° and the surface is hydrophobic if the value of the contact angle is greater than 90°. Surfaces with the contact angle between 150° and 180° are called superhydrophobic. The contact angle is related to several factors, such as surface energy, roughness, the surface preparation process, and surface cleanliness [1-4]. Hydrophobic surfaces are used for several purposes such self cleaning [5, 6], anti adhessive coatings [7], textile [8], biomedicine [9] and so on.

Water-repellent surfaces can be prepared by using low surface energy materials. The hydrophobicity of a surface can also be increased by increasing the surface area. Increasing surface roughness creates air pockets and causes increasing surface area. Air may be trapped in the holes of rough surface, resulting in a composite solid–air–liquid interface, as opposed to the homogeneous solid–liquid interface [10-13].

Hydrophilic behavior is generally observed by surfaces with critical surface tensions greater than 45dynes/cm. As the critical surface tension increases, the expected decrease in contact angle is accompanied with stronger adsorptive behavior and with increased exotherms associated with the adsorption. Hydrophobic behavior is generally observed by surfaces with critical surface tensions less than 35dynes/cm.