title: Control of superhydrophilicity/superhydrophobicity using silicon nanowires via electroless etching method and fluorine carbon coatings.
abstract: Surface roughness is promotive of increasing their hydrophilicity or hydrophobicity to the extreme according to the intrinsic wettability determined by the surface free energy characteristics of a base substrate. Top-down etched silicon nanowires are used to create superhydrophilic surfaces based on the hemiwicking phenomenon. Using fluorine carbon coatings, surfaces are converted from superhydrophilic to superhydrophobic to maintain the Cassie-Baxter state stability by reducing the surface free energy to a quarter compared with intrinsic silicon. We present the robust criteria by controlling the height of the nanoscale structures as a design parameter and design guidelines for superhydrophilic and superhydrophobic conditions. The morphology of the silicon nanowires is used to demonstrate their critical height exceeds several hundred nanometers for superhydrophilicity, and surpasses a micrometer for superhydrophobicity. Especially, SiNWs fabricated with a height of more than a micrometer provide an effective means of maintaining superhydrophilic (<10°) long-term stability.
authors: Department of Mechanical Engineering, Yonsei University, 262, Seongsanno, Seodaemun-gu, Seoul 120-749, Korea.
authors: Beom Seok
authors: BS
authors: Kim
authors: Sangwoo
authors: S
authors: Shin
authors: Seung Jae
authors: SJ
authors: Shin
authors: Kyung Min
authors: KM
authors: Kim
authors: Hyung Hee
authors: HH
authors: Cho
mesh_terms: D002244:Carbon / Q000737:chemistry*; D005461:Fluorine / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D053770:Nanowires / Q000737:chemistry*; D012825:Silicon / Q000737:chemistry*
chemical_list: D005461:Fluorine; D002244:Carbon; D012825:Silicon