Fabrication of a superhydrophobic and oleophobic PTFE membrane: An application to selective gas permeation

• Omniphobic PTFE was fabricated with FOTS by either dip-coating or vapor deposition.
• Vapor-deposited FOTS-PTFE lost initial oleophobicity due to its porous structure.
• Dip-coated FOTS blocked intrinsic pores of PTFE, resulting in a stable omniphobicity.
• Dip-coated FOTS-PTFE showed gas permeability towards CO2 and DMMP vapor.

A superhydrophobic and oleophobic film was fabricated on polytetrafluoroethylene (PTFE) using SiO2 nanoparticles and 1H,1H,2H,2H-perfluorooctyltrichlorosilane (FOTS). The surface of the bare PTFE sheet was first coated with SiO2 nanoparticles by the dip-coating method, and FOTS was subsequently deposited on the SiO2-coated PTFE by either dip-coating or vapor deposition. Both of the FOTS-coated PTFE samples prepared using either dip-coating or vapor deposition initially showed high repellence towards water and hexadecane droplets. The FOTS-PTFE prepared by vapor deposition gradually absorbed hexadecane. By contrast, the dip-coated FOTS-PTFE displayed a durable non-wetting property, even after exposure to acidic/basic solutions and UV light irradiation. Gas permeability of the prepared superhydrophobic and oleophobic PTFE sheets towards CO2 and dimethyl methylphosphonate (DMMP) vapor was also determined. We suggest that our superhydrophobic and oleophobic membrane could be used as the shielding layer of a gas sensor, to repel various liquids and only allow transmission of gases.

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