Seamless micro and nanopatterned drum molds based on ultrasonic indentation

Roll-to-roll nanoimprint lithography offers a method to scale functional micro and nanopatterned surfaces for a wide array of applications. However, creating a sufficiently large, seamless drum mold is still often prohibitively expensive or impossible. This patterning becomes especially difficult when the periodicity of the pattern is smaller than half the wavelength of visible light, the limit for UV interference lithography. High-speed indentation via a novel process called “Nanocoining” has been demonstrated to overcome this issue. Thus far, Nanocoining has been used to create cylindrical molds up to 6.5 inches in diameter and 6 inches in length with a patterning rate of more than one square inch per minute. The process has been demonstrated with features between 250 nm and 5 μm in pitch (center-to-center distance) and aspect ratios (height:pitch) of up to 0.6, and the resulting molds have successfully embossed into more than 500 linear feet of film. In this proceeding, we will present the background and state of the art of this technology as well as recent efforts to control feature shape for applications like microlens arrays. We’ll also introduce new concepts, including using indentation to create seamless, cylindrical photomasks for roll-to-roll patterning of resists without the residual layer that is typically left behind by nanoimprint lithography.