Microlens arrays fabricated by a direct ink-jet printing of UVcurable hybrid polymer are reported. A periodic pattern of polymer drops was ink-jet printed on the surface-treated glass substrate and cured in the UV-light. Using this simple technique, we demonstrated periodic arrays of almost semi-spherical microlenses of 50 µm diameter size and a focal distance of 48µm. The optical characteristics of solitary µ-lenses and arrays comprising up to 64x64 microlenses are measured both in the near-and farfield zones. Large numerical aperture and short focal distance make the inkjet printing of microlenses very attractive for applications in optical interconnects, large 2D VCSEL arrays and pixelated imagine sensors utilizing CCD or SPAD arrays, offering thus an efficient, simple and a cheap alternative to the conventionally used photolithography technique.
An epoxy‐based negative‐tone photoresist, which is known as a suitable material for high‐aspect‐ratio surface micromachining, is functionalized with red‐light‐emitting CdSe@ZnS nanocrystals (NCs). The proper selection of a common solvent for the NCs and the resist is found to be critical for the efficient incorporation of the NCs in the epoxy matrix. The NC‐modified resist can be patterned by standard UV lithography down to micrometer‐scale resolution, and high‐aspect‐ratio structures have been successfully fabricated on a 100 mm scaled wafer. The “as‐fabricated”, 3D, epoxy‐based surface microstructures show the characteristic luminescent properties of the embedded NCs, as verified by fluorescence microscopy. This issue demonstrates that the NC emission properties can be conveniently conveyed into the polymer matrix without deteriorating the lithographic performance of the latter. The dimensions, the resolution, and the surface morphology of the NC‐modified‐epoxy microstructures exhibit only minor deviations with respect to that of the unmodified reference material, as examined by means of microscopic and metrologic investigations. The proposed approach of the incorporation of emitting and non‐bleachable NCs into a photoresist opens novel routes for surface patterning of integrated microsystems with inherent photonic functionality at the micro‐ and nanometer‐scale for light sensing and emitting applications.
Inkjet technology is a compelling method for the flexible and cost-effective printing of functional inks. We show that nanocomposite solutions based on polystyrene and differently sized core/shell-type nanocrystals (NCs) formed by a CdSe core coated with a shell of ZnS (CdSe@ZnS) in a single solvent, chloroform, can be reliably dispensed into luminescent, multicolor pixel arrays. This study demonstrates the relevance of parameters like polymer concentration and nozzle diameter, highlighting how the optimal conditions to print NCs embedded in 5 wt% polystyrene nanocomposite are given by a 70-mmdiameter nozzle. The obtained structures show that the bright size-dependent emission of the NCs in the nanocomposite is retained in the printed pixels.
This paper describes a novel method to fabricate polymer MEMS based on the inkjet printing of SU-8, with a special emphasis on integrated micro-optical lens arrays. Inkjet control parameters are optimized in order to enable a stable and reproducible ejection of SU-8 drops in both continuous and drop-on-demand (DOD) modes. Arbitrary patterns of single and multiple polymer drops and arrays of convex microlenses are printed on different substrates. The influence of surface wetting properties on the size and the shape of the printed patterns is investigated. The optical properties of the microlenses are investigated in details. A model for inkjet printing of high-viscous functional materials for polymer MEMS has been used.
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