A Simple Method for obtaining Perforated Supporting Membranes for Electron Microscopy

Abstract

SUPPORTING membranes with holes are usually used for testing the axial astigmatism of the objective lens in electron microscopy. In the case of specimens which are difficult to focus they facilitate the focusing. Supporting membranes with a large percentage of open area are of great advantage for mounting thin sections, because the gain in contrast is considerable¹. It applies also to specimens for testing the resolving power of the electron microscope or high-resolution work, when a very thin film of collodion can be mounted on these perforated membranes². The holes will then enable not only the focusing but also a continuous control of the axial astigmatism. Several methods for obtaining holes in supporting membranes have been described^3–5. Mostly ‘Formvar’ film is used; but to obtain reproducible results the methods are relatively complicated.