Energy Barrier Confined Electrohydrodynamic Printing Microlens Arrays with Wide Range Tunability of Numerical Aperture and Record-High Resolution.

Microlens arrays (MLAs) are integral to a wide range of optical applications such as displays and sensors. Printing-based approaches offer distinct merits in MLAs fabrication including design flexibility, efficient material usage, and superior surface quality. However, existing MLAs printing technologies remain constrained by the fundamental droplet-substrate coupling that fixes the contact angle, restricting the tunability of the curvature and numerical aperture (NA) of microlenses. Here, we introduce an energy-barrier-confined electrohydrodynamic (EHD) printing approach that enables programmable geometric control of MLAs morphology. By introducing energy barrier construction through precisely patterned wettability contrast, the robust constraint of the droplet radius is accomplished. The multilevel tuning in curvature is achieved through the precise control of dosing volume and landing position during EHD printing, which supports wide NA tunability (0.2 to 0.508) in MLAs, and further enables the fabrication of complex multifocal MLAs, as experimentally demonstrated. The fabricated MLAs exhibit ultrasmooth surfaces and record-high imaging resolution of 23091 ppi. This study shows a roadmap for precise geometric programming of high-performance MLAs, with promising potential for use in integral imaging and high-resolution displays.