Scaling approach toward nano electro-discharge machining: Nanoscale patterning of carbon nanotube forests

• We found out an approach to pushing the resolution limit of μEDM down to the nanometer scale.
• A scaling effect of electrode size on decreasing working voltage was demonstrated both experimentally and theoretically.
• Reduction of discharge pulse energy due to the decreasing working voltage was achieved and improved the resolution of μEDM.
• Nano-scale structures were fabricated on carbon nanotube forests using reduced size of electrode.

Micro-electro-discharge machining (μEDM) is a versatile technique for micromachining of electrically conductive materials with resolutions limited within the micrometer scale. This paper reports an approach to pushing the resolution limit of μEDM down to the nanometer scale. EDM with different electrode tip sizes is performed on carbon nanotube forests and the results reveal a favorable scaling effect of the tip size on the working voltage required for the breakdown of the dielectric between the electrode and workpiece, suggesting that downsizing of the electrode tip assists in the reduction of the discharge pulse energy. Based on this finding, controlled patterning of grating-like structures with ~ 200 nm height is demonstrated on carbon nanotube forests with an estimated pulse energy of 1 nJ, achieved using a tungsten electrode with a tip radius of 3 μm. Theoretical analysis of this process setting shows a close match with the experimental results, further supporting the scaling effect. These results suggest the feasibility of the approach toward “nano-EDM” for an extensive range of potential applications in micro/nanodevice and nanotechnology areas.

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