A Novel Approach for the Fabrication of Silica and Silica/Metal Hybrid Microtubes

This paper describes a novel and simple method to fabricate silica and silica/metal hybrid microtubes of very high aspect ratio via self-rolling of polymer layers. A trilayer of poly(dimethylsiloxane) (PDMS)/polystyrene (PS)/poly(4-vinylpyridine) (P4 VP) self-rolled into microtubes, when exposed to a solvent selective for P4 VP chains, because of the strain generated by the swelling of P4 VP layer. Oxidative pyrolysis of the polymer tubes at 700 degrees C removes all the organic part of the tube and converts PDMS into silica. Moreover, by depositing a metallic layer on the tripolymer layer, it was possible to obtain silica/metal hybrid tubes. The metallic layer can form the inner or outer wall of the tube by depositing it over or under the PDMS layer. The fabricated tubes were further characterized by optical microscopy, Fourier transform infrared (FTIR), high-resolution scanning electron microscopy (HRSEM), X-ray photoelectron spectroscopy (XPS), energy-dispersive analysis (EDX), Si-29 solid-state nuclear magnetic resonance (Si-29 NMR), and focused ion beam (FIB). The silica and silica/metal hybrid tubes have potential applications in micro- and nanofluidic devices, optoelectronic devices, and in catalysis.