Hollow medical fibers are simply polymeric fibers that have a continuous hole running down the middle , which is created by introduction of air or other gas (nitrogen) in the polymer solution (in wet spinning process or by melt spinning through specially designed spinnerets , having a wide – ranging and precise control of wall thickness and diameter in the course of production
The Fibers must be porous in order to act as a filter. Porosity must be structured in the fibers. One method of doing this is to add a soluble particulate into the polymer before is made into a hollow fiber. This material is then dissolved out of the fiber by passing it through a leaching solution. This method is used for making hollow fibers from both melt spun or solution – spun precursors. In another method a hollow fiber is melt spun and then subject to a cryogenic gas that actually shatters the polymer to cause voids
Hollow Fiber with porous wall structure (hollow membranes with a very large surface / volume ratio in a smallest space have found increasing access to hemodialysis and they have replaced coil and laminate in dialyzer devices.