Patterning of Microstructures on SU-8 Coated Flexible Polymer Substrate Using Roll-to-roll Ultraviolet Nanoimprint Lithography

In the present work, 2.2μm-wide line gratings are continuously patterned onto a SU-8 coated flexible polymer substrate using an in-house designed roll-to-roll ultraviolet nanoimprint lithography (R2R-UV-NIL) system. A master mold was first produced by patterning the silicon wafer coated with Microresist s ma-N2410 electron sensitive negative photopolymer with line grating patterns using electron beam lithography (EBL) process. A flexible replica of the master mold was then produced using heat-curable poly-dimethyl-siloxane (PDMS) via cast molding process to be used as the flexible mold in the imprint lithography process. Using a commercially available 50 μm-thick polyethylene terephthalate (PET) film as the flexible substrate and fast curing SU8-2002 UV-curable negative photopolymer as the imprint resist, continuous patterning of the line grating structures has been carried out at the speeds of 50, 100 and 150 mm min^–1 using the R2R-UV-NIL imprinting tool. The atomic force microscopy (AFM) measurements of the imprints showed good pattern quality and reproducibility for all three speeds. This work has demonstrated that R2R-UV-NIL is a promising technique and tool for fabricating microstructures on flexible substrate for future applications.