Figure S2 from PEEK surface modification by fast ambient-temperature sulfonation for bone implant applications

Schematic diagram depicting a water droplet on (a) a smooth surface, (b) a rough surface in the Wenzel wetting state, adapted from reference [26] with permission. Red dashed line in (b) indicates the projected surface of the roughened wet surface on the apparent solid plane. θ and θ* are respectively the contact angle on smooth surface and the corrected contact angle on the rough surface based on the Wenzel equation. (c) Schematic diagram for calculating the roughened wet surface area.