We show that, in Parylene films fabricated by Parylene-on-liquid-deposition (POLD), the side in contact with the liquid during deposition develops a porous surface. Because of the liquid nature of such a deposition substrate, the molecules of Parylene monomer can diffuse into and polymerize inside the liquid, which is probably the main cause of this effect. We also found that the dimension of the characteristic features on such a surface as well as the thickness of the porous domain becomes larger when a liquid with larger molecular weight is used. We demonstrate three applications using this interaction between liquids and Parylene: POLD films as gas exchange membranes, POLD as a method to modify the hydrophobicity of Parylene surface, and in pattern-selective deposition of POLD films.

References :
Nguyen Binh-Khiem, Kiyoshi Matsumoto, and Isao Shimoyama, "Porous Parylene And Effects of Liquid on Parylene Films Deposited on Liquid,”IEEE 24th International Conference on Micro Electro Mechanical Systems (MEMS '11), pp. 513-516, Cancun, Mexico, Jan. 23-27, 2011． [Proceedings]