These tubes can be made from many materials such as polymers, ceramics and metals that can be applied to a surface of...http://www.google.ca/patents/US5352512?utm_source=gb-gplus-sharePatent US5352512 - Microscopic tube material and its method of manufactureAdvanced Patent SearchPublication numberUS5352512 APublication typeGrantApplication numberUS 07/980,317Publication date4 Oct 1994Filing date16