Drop-on-Demand Electrohydrodynamic Jet Printing of Microlens Array on Flexible Substrates

Abstract

The inkjet-printing technique is regarded as an efficient method to fabricate microlens arrays used in digital cameras, medical endoscopes, displays, optical communication, and light source devices. The diameter, height, and aspect ratio of the microlens are the major contributors to these optical properties. Hence, the optical characteristics of the microlens array can vary with the type of inkjet-printing method. In this study, by employing electrohydrodynamic (EHD) jet printing with the drop-on-demand strategy, we fabricated microlenses and microlens arrays using a UV-curable photopolymer liquid on flexible poly(3,4-ethylenedioxythiophene):polystyrenesulfonate-coated poly(ethylene terephthalate). By controlling the number of printing drops, which is regarded as an efficient approach to control the dimension of the microlens, lenses with diameters of 11.9 ± 0.2 and 24.4 ± 0.5 μm and aspect ratio ranging from 0.22 to 0.33 were constructed. It was found that the focal length (15.44–26.79 μm), numerical aperture (0.39–0.46), and f-number (1.3–1.1) varied with the number of printing drops. The results demonstrate that the EHD-printed microlenses have a much shorter focal length, higher numerical aperture, and smaller f-number than the previously reported printed lenses. Hence, the EHD-printed microlens can be utilized to produce wide-angle-of-view applications and capture accurate images with insufficient light intensity. In addition, the proposed EHD-printing method may provide a cost-effective and simple route for manufacturing microlens arrays.