Abstract
Plano-convex microlens arrays of organic-inorganic polymers with tailored optical properties are presented. The fine-tuning of each microlens within an array is achieved by confining inkjet printed drops of the polymeric ink onto pre-patterned substrates. The lens optical properties are thus freely specified, and high numerical apertures from 0.45 to 0.9 and focal lengths between 10 μm and 100 μm are demonstrated, confirming theoretical predictions. Combining nanoimprint lithography approaches and inkjet printing enables using the same material for the microlenses and their substrates, improving the optical performances. Microlens arrays with desired specifications are printed reaching yields up to 100% and high lens reproducibility with standard deviations of the apparent contact angle under 1° and of the numerical apertures and focal lengths under 6%. Microlens arrays involving lenses with different characteristics, e.g. multi focal length, and thus focal planes separated by only few microns are printed with the same reproducibility.
Highlights
The demand of micro optical elements, such as microlens arrays (MLA) with specific and precise lens features, has increased in the last decades in very broad fields of application such as Light-Emitting Diode (LED) displays [1], Shack-Hartmann wave front sensors, photolithography [2], biomedical technologies [3], optical interconnects [4] and more recently optical security features [5]
In this work we present polymeric MLAs with precise and reproducible single and multiple lens characteristics developed by means of Inkjet printing (IJP)
We demonstrate that by printing a specific ink volume on a pre-patterned platform, microlenses with targeted and specific geometries as well as optical characteristics could be printed
Summary
The demand of micro optical elements, such as microlens arrays (MLA) with specific and precise lens features, has increased in the last decades in very broad fields of application such as Light-Emitting Diode (LED) displays [1], Shack-Hartmann wave front sensors, photolithography [2], biomedical technologies [3], optical interconnects [4] and more recently optical security features [5]. Based on IJP dispensing, the minimum rim height of protrusive platforms with vertical side walls allowing liquid confinement has been demonstrated to be slightly lower than 1 μm [23] This principle has been successfully applied for the fabrication of arrays of plano-convex lens-like structures with controlled spherical profiles [22,24]. Controlled volumes of InkOrmo are locally deposited and confined onto such platforms by drop-on-demand IJP to form the microlenses This allows a fine control of each microlens profile, of their optical specifications, achieving MLAs with highly repetitive characteristics from lens to lens. It is proven that lenses with different concrete specifications can be printed on the same MLA with high optical quality and low technological complexity
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