Experimental and Numerical Modeling of the Controllable Wettability Gradient on Poly(propylene) Created by SF₆ Plasma

A continuous and scalable wettability gradient of water contact angle (WCA) (20–135°) were successfully prepared on poly(propylene) film by applying O 2 plasma for pretreatment followed by SF 6 plasma treatment under a specially designed mask. Moreover, the role of mass transfer processes in the plasma treatment leading to the gradient formation was clearly described in mathematical terms. By mathematical analyses, a mass transfer coefficient calculated from the sample of 1 cm was employed for scaling‐up process to create gradients on sample length of 5 cm and 7 cm. ESCA analysis revealed that the incorporation of C–F bonds resulted in hydrophobicity on the surface and the formation of the gradient. The wide‐range wettability gradient was demonstrated as an effective tool for screening cell behaviors as demonstrated by culturing L‐929 fibroblast cells on the gradient. magnified image