Patterning of multi-leveled microstructures on flexible polymer substrate using roll-to-roll ultraviolet nanoimprint lithography

The recent developments of flexible electronics, biochips, optical devices and micro/nano-electro-mechanical-systems (MEMS/NEMS) have featured various complex three-dimensional or multileveled micro/ nano structures in its designs. However, fabricating these structures using the existing technologies such as photolithography and electron beam lithography (EBL) are time consuming and involved high process costs. Nevertheless, the production of these microstructures at high volume manufacturing scale has led to the demand for a simpler, low-coat and high-throughput technique for patterning process. In the present work, multi-level microstructures (3-levels) with minimum feature size of approximately 50 µm are continuously patterned onto flexible polymer substrate using in-house designed roll-to-roll ultraviolet nanoimprint lithography (R2R-UV-NIL) system. Using a commercially available 50µm-thick polyethylene terephthalate (PET) film as the flexible substrate and SU8-2002 photopolymer as the imprint resist, continuous patterning of the multi-level structures has been demonstrated at speed of 100 mm/min using R2R-UV-NIL imprinting tool. Ten imprints were produced consecutively, where the confocal laser scanning microscopy (CLSM) measurements of the imprints demonstrated the potential of the R2R-UV-NIL technique to replicate multi-level structures, albeit the pattern waviness or plane flatness issue due to the deformation of the soft PDMS mold. With further process optimization and usage of a harder mold material, the R2R-UV-NIL is a promising technique and tool for fabricating complex 3D and multi-level microstructures on flexible substrate for future applications.