Silica coating of polymer nanowires produced via nanoimprint lithography from femtosecond laser machined templates.

In this paper we report on the fabrication of regular arrays of silica nanoneedles by deposition of a thin layer of silica on patterned arrays of polymer nanowires (or polymer nanohair). An array of high-aspect-ratio nanoscale diameter holes of depths greater than 10 µm was produced at the surface of a fused silica wafer by an amplified femtosecond laser system operated in single-pulse mode. Cellulose acetate (CA) film was imprinted into the nanoholes and peeled off to form a patterned array of standing CA nanowires, a negative replica of the laser machined nanoholes. The cellulose acetate replica was then coated with silica in a chemical vapor deposition process using silicon tetrachloride vapor at 65 °C. Field emission scanning electron microscopy, focused ion beam sectioning, energy dispersive x-ray analysis and Fourier-transform infrared spectroscopy were used to characterize the silica nanoneedles. Precisely patterned, functionalized arrays of standing silica nanoneedles are useful for a number of applications.