Advanced application of atmospheric-pressure plasma jet using a surgical needle to microfabrication

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Atmospheric-pressure microplasma jets (AP μ PJs) of Ar, Ar/0_2 and air were generated from the tip of a stainless steel surgical needle having outer and inner diameter of 0.4 and 0.2 mm, respectively, with a rf excitation of 13.56 MHz. The steel needle functions both as a powered electrode and gas nozzle. The operating power is 1-6 W and the corresponding peak-to-peak voltage is about 1.5 kV. The AP μ PJ was applied to the localized etching of a polyamide-imide insulator film (thickness of 10 μ m) of a copper winding wire of 90μ m diameter. The insulator film around the copper wire was completely removed by the irradiated plasma from a certain direction without fusing the wire. The removal time under the Ar AP μ PJ irradiation was only 3 s at a rf power of 4 W. Fluorescence microscopy and scanning electron microscope images reveal that good selectivity of the insulator film to the copper wire was achieved.Vertically aligned bundles of multiwalled carbon nanotubes (MWNTs) were grown on the tip of a φ 0.5 mm Ni wire using an AP μ PJ generated by a RF-powered surgical needle. A CH_4/H_2 gas mixture was used for the source gas, and the Ni wire used as the substrate was negatively biased to heat it by ion bombardment. At a ratio of CH_4:H_2=1:35,a RF power of 6 W, a DC bias voltage of-100 V and a growth time of 2 min, the tip of the Ni wire was covered by bamboo-like MWNT bundles, whose diameter and length were about 600 nm and 2-3μm, respectively. Each bundle consisted of about 1500 tubes with diameters of 10-25 nm. The growth temperature of the MWNT bundles was approximately 500℃.