Elliptical vibration chiseling: a novel process for texturing ultra-high-aspect-ratio microstructures on the metallic surface

High-aspect-ratio metallic surface microstructures are increasingly demanded in breakthrough applications, such as high-performance heat transfer enhancement and surface plasmon devices. However, the fast and cost-effective fabrication of high-aspect-ratio microstructures on metallic surfaces remains challenging for existing techniques. This study proposes a novel cutting-based process, namely elliptical vibration chiseling (EV-chiseling), for the high-efficiency texturing of surface microstructures with an ultrahigh aspect ratio. Unlike conventional cutting, EV-chiseling superimposes a microscale EV on a backward-moving tool. The tool chisels into the material in each vibration cycle to generate an upright chip with a high aspect ratio through material deformation. Thanks to the tool's backward movement, the chip is left on the material surface to form a microstructure rather than falling off. Since one microstructure is generated in one vibration cycle, the process can be highly efficient using ultrafast (>1 kHz) tool vibration. A finite element analysis model is established to explore the process mechanics of EV-chiseling. Next, a mechanistic model of the microstructured surface generation is developed to describe the microstructures' aspect ratio dependency on the process parameters. Then, surface texturing tests are performed on copper to verify the efficacy of EV-chiseling. Uniformed micro ribs with a spacing of 1-10 mu m and an aspect ratio of 2-5 have been successfully textured on copper. Compared with the conventional EV-cutting that uses a forward-moving tool, EV-chiseling can improve the aspect ratio of textured microstructure by up to 40 times. The experimental results also verify the accuracy of the developed surface generation model of microstructures. Finally,the effects of elliptical trajectory, depth of cut, tool shape, and tool edge radius on the surface generation of micro ribs have been discussed.