A new method to manufacture parylene microcapillaries
A new way to fabricate extremely long and uniform Parylene microcapillaries with a minimum inner diameter of 3 μm and a length exceeding 30 cm is reported here. The method starts with drawing sacrificial poly(ethylene carbonate) (PEC) fibers from its chloroform solution and then forms hollow capillaries by coating the fibers with Parylene and removing the sacrificial PEC at its thermolytic temperature. For the fiber drawing, the relation of fiber diameter to other parameters including drawing speed, fiber aspect ratio, solution viscosity and solvent evaporation rate are studied at 0 and 25 °C. It is found that 0 °C is near the optimal temperature in terms of fiber diameter uniformity. Finally, this work also reports a self-expelling mechanism of the molten PEC at its thermolytic temperature from inside the Parylene-coated PEC fibers, which greatly reduces the sacrificial time to only tens of minutes.