Fabrication of a thin-layer PTFE coating exhibiting superhydrophobicity by supercritical CO2.

A new process for deposition of a thin-layer coating of Poly(tetrafluoroethylene) (PTFE) on a glass substrate exhibiting superhydrophobicity using supercritical carbon dioxide (sc-CO 2 ) was reported. The process involved placing a PTFE source material and the glass substrate to be coated inside an autoclave in supercritical carbon dioxide (sc-CO 2 ), maintained at 300 °C temperature and 24 MPa, for a time period. The variations in the surface morphology and wetting characteristics of both the coated glass substrate and the PTFE source specimen with increasing time period of the process have been investigated. The morphology of the surfaces was investigated by scanning electron microscopy while the wetting characteristics by contact angle measurement. The surface of the glass substrates was found to be increasingly deposited with minute globulets of PTFE with increasing time of the process. The static water contact angle measured on the coated substrates increased with increasing coating time and the coated substrates showed superhydrophobicity when the coating time exceeds a certain time period. The PTFE source specimen surface became increasingly rough with micron-sized surface swellings and protrusions appearing on the surface with increasing time of the process and showed superhydrophobicity when exposed in the supercritical environment for certain time period. The method may find use in fabricating a thin-layer coating of PTFE for potential microelectronics, microfluidics and sensor applications. [ABSTRACT FROM AUTHOR]