Directed ion beam sputter etching of polytetrafluoroethylene (Teflon) using an argon ion source

Abstract

Polytetrafluoroethylene (Teflon) tubes of outside diameter 375–625 μm were perforated by bombarding the tubes with an argon ion beam. Holes of diameter 18 μm and 40 μm on a side and open-area ratios of 55% and 65% respectively were formed using electroformed nickel mesh masks. Scanning electron micrographs of the hole walls reveal that they are relatively smooth and that the holes go completely through the tubing walls. Holes with the smoothest walls and the sharpest definition were obtained by using low beam power densities and a tubing target temperature of less than 50°C. Volumetric flow rate measurements show that the flow rate through the perforated tubules is 0.2-0.5 cm 3 min -1 for a pressure drop across the tubes of 2.2 Torr. The perforated microtubules have an important application in medicine for sufferers of hydrocephalus, a malady which results in the build-up of cerebrospinal fluid in the brain. The perforated tubing is inserted into the ventricle and serves as a shunt by draining off the excess cerebrospinal fluid into another part of the brain, where the fluid is absorbed by normal processes.