Imaging of filtration channels in track membranes by the Schwarzschild X-ray microscope

Abstract

Nowadays, one of the most widespread technological processes for separation of complex mixtures is membrane filtration. Among the materials used in this process, an important role is played by track membranes (nuclear filters) manufactured by means of irradiating polymeric films by high-energy ion beams with the subsequent etching tracks until pores have been obtained [1]. The distinctive features of track membranes compared to traditional ones are their high selectivity with respect to particles to be filtered, low adhesion ability, and inertial behavior with respect to a large number of compounds—including also biological objects. The track membranes are used in the processes of purification, concentration, and filtration of viruses, for purging vaccines of medicine solutions [2], etc. These membranes are also promising in developing means for protecting respiratory organs against unfavorable actions. Determining the geometrical dimensions of filtration channels in track membranes is rather significant for using them efficiently. Meanwhile, the solution of this problem is not evident in the case of pore diameters smaller than 0.5 μ m. Standard methods of optical microscopy make it impossible to resolve such sizes, while electron and X-ray microscopy (wavelengths of 0.05 to 0.3 nm) require additional processing of the surface for materials under study.