Direct fabrication of microlens arrays with high numerical aperture by ink-jetting on nanotextured surface

This work presents an economic method for fabricating solid microlens array (MLA) of high numerical aperture (NA) from UV-curable polymer by micro-droplet jetting. The prepolymer is ink-jet on a substrate with an omniphobicity enhanced by nanotexturing and octafluorobutane (C4F8) coating, leading to a significantly increased contact angle, therefore, an increased droplet curvature. ZnO nanopillars (NPs), which can grow economically on the substrate with a well-controlled morphology, are generated to serve the nanotexturing. Meanwhile, the ZnO NPs can effectively suppress total reflection of incidence light without introducing obviously spectral changes and directionality, which is positive for the performance of MLAs fabricated on it. Since the micro droplets can be arrayed precisely with a uniform volume, after the solidification, high quality MLAs of NA = 0.52 with smooth surface, good uniformity and reproducibility are fabricated.