Fabrication of multi-scale micro-lens arrays on hydrophobic surfaces using a drop-on-demand droplet generator

•We provide a simple drop on demand droplet generator for fabricating the microlens.•We fabricate the microlens with variety of sizes and radii on different substrates.•The numerical aperture of the microlens can be controlled ranging from 0.09 to 0.47.

A simple method was demonstrated for the fabrication of multi-scale polymer microlenses (µ-lenses) and microlens arrays (MLAs) using a drop-on-demand (DOD) droplet generator. A ultraviolet (UV) curable polymer used as the ink was DOD printed on the hydrophobic surfaces with different wetting conditions and cured by a UV lamp. The high quality µ-lenses and MLAs with good geometrical uniformity were fabricated. The shapes of the µ-lenses and MLAs were controlled by the different surface wetting conditions, and these shape changes affected the optical properties of the µ-lenses and MLAs, such as the numerical aperture (NA), focal distance (f) and the f-number (f#). The surface roughness of the µ-lens was measured by a white light interferometer (VSI mode) and atomic force microscope (AFM) and proved satisfactory. The influences of the surface wetting conditions on imaging and light gathering characteristics of the MLAs were evaluated by an optical microscope.