Ultrasonic Nanocoining to Create Large Arrays of Sub-Wavelength Features

S. Furst
Smart Material Solutions, LLC,
United States

Keywords: Nano-fabrication, structured surfaces, anti-reflective, super-hydrophobic,

Summary:

Nanocoining is a novel manufacturing process that can rapidly coat a meter-square area hardened metal surface with features that are smaller than the wavelength of visible light (< 300 nm) by indenting them using a diamond die. The features can give a surface anti-reflective or enhanced/non-wetting properties. The technology can be used to indent features into a metal drum mold for roll-to-roll processes, facilitating massive scale-up into polymer films. Nano-features are indented into the metal surface using a 20x20 μm diamond die with 250 nm wide and 150 nm tall features created by FIB machining. The die presses into the surface 45,000 times per second using an ultrasonic resonant actuator mounted to a diamond turning lathe. At this rate, a 1 sq-meter area can be coated in 18 hrs. Current machining methods rely on scraping material away with a sharp tool and cannot create features on nano-scale. This is because any tool sharp enough to create such a small feature will be prohibitively fragile and susceptible to rapid wear. Indenting is fundamentally different and has been used for millennia to create coins. No material is removed; it is simply pushed aside, leaving behind the pattern on the die. Furthermore, indenting drastically reduces the abrasive wear process caused when a diamond tool slides against a metal work-surface. Nanocoining has the advantage of working at room temperature, and it offers the potential for higher through-put and less stringent process control than many other chemical or light-based nano-fabrication methods. This technology will provide a new nano-manufacturing method for industries including solar photovoltaics, LED/OLED, auto/residential glass, and optics.