Basics of track-etching

First step of track-etching process consists in the beaming of a thin polymer film with energetic heavy particles leading to the creation of linear damaged tracks across the polymer.

• ECR heavy ion source to generate a plasma and to selectively extract charged ions.
• Cyclotron to accelerate beams of selected ions (Ar, Kr, Xe).
• Under vacuum chamber for the continuous beaming of rolls of polymer films.

The density of tracks (number of tracks per unit area of film) is defined by the ion beam intensity and by the linear speed of the film. Linear tracks created during the beaming are mainly characterized by macromolecular chain scissions, highly hydrophilic chemical groups and free vacuum. Tracks are therefore more sensitive to chemicals than surrounding bulk polymer and can be selectively etched leading to their revelation into pores (second step of track-etching process).

Specifications of pores (pore diameter and pore shape) are defined by etching conditions (chemicals, temperature, duration, …).