US Patent 7419612 - Method of fabricating nanoporous polyimide film

http://www.freepatentsonline.com/7419612.html

This patent teaches a method of making nanoporous films of polyimide which is capable of maintaining favorable properties over an extended temperature range. Claim 6 reads:

6. A method of creating pores of nanometric to micrometric size in a thin sheet of polyimide, in which the sheet is subjected to the steps comprising:

an ion bombardment;

a radiation in the visible range of a halogen light emitting at wavelengths of between 450 and 530 nm for a period of about 10 hours to one week; and

a chemical etching.