Step and scanning lithography for patterning seamless microstructures on the inner surface of a hollow roller

This paper presents a step-and-repeat photolithography method for patterning seamless microstructures on the inner cylindrical surface of a hollow roller. The purpose is for subsequent replication of the microstructures onto the surface of another mold for roller imprinting. The processes include coating of a photoresist (PR) layer, ultraviolet (UV) exposing the PR layer with a photomask, and finally PR developing to obtain patterned microstructures on the inner cylindrical surface. To achieve seamless patterning, UV exposure process is first conducted locally on a narrow and slender area and then consecutively repeated. Through efforts on precision mechanical system design and using a collimated UV light source, consecutively exposed areas can be seamlessly stitched together to form a complete UV exposed pattern on the inner cylindrical surface. Experiments have been carried out using three photomasks with hexagonal arrays of hexagons and circles. Typical feature sizes are around ten to a few tens of micrometers. Details on the experimental results as well as future perspectives on the applications of this new type of lithography for roller imprinting will be addressed.