Fabrication of metallic microtubes using self-rolled polymer tubes as templates

We present a novel approach for fabricating single and bimetallic (gold, titanium) (Au, Ti, Au/Ti) microtubes with very high aspect ratio from self-rolled polymer templates. The polymer microtubes used as the template were generated by self-rolling of thin polymer bilayer films (polystyrene/poly(4-vinylpyridine) (PS/P4VP) gradually released from a solid substrate. The self-rolling was introduced in the polymer bilayer by swelling the bottom P4VP layer in dodecylbenzenesulfonic acid (DBSA) solution, which was opposed by a stiff top PS layer. The inner wall of the tube was metallized by depositing a thin layer of desired metal on top of the bilayer by physical vapor deposition. The polymer template was then removed by pyrolysis, resulting in pure metal microtubes, which were characterized by optical microscopy, scanning electron microscopy (SEM), infrared spectroscopy (IR), energy-dispersive X-ray (EDX), and X-ray photoelectron spectroscopy (XPS). The tube diameter was tailored by changing the metal layer thickness on the polymer bilayer. The approach described here is general and could be used to fabricate any type of single or multimetallic tube. The metal microtubes reported in this method have potential application in drug delivery systems, microelectronics, microfluidic devices, enzyme bireaction, and chemical and biochemical sensing devices.