3D Printed Freeform Lenses with Nanoimprinted
Moth-Eye Antireflective Structures
Amiya R. Moharana, Pavel Kulha, Michael J. Haslinger, Michael Mühlberger andDaniel Fechtig
PROFACTOR GmbH, Steyr, 4407, Austria
E-mail: amiya.moharana@profactor.at

Several studies point out the challenge to produce controlled patterned nanostructures on thesurface of complex 3D fabricated objects. Micromolding and soft lithography have been used togenerate micro and nanoscale topographical features on planar and non-planer substrates. Somedevelopments aim at structuring nanoscale features directly on the surface of 3D printed objects(e.g. chemical etching or plasma surface modification). Incorporating the Moth-Eye structures for
Anti-Reflection (AR) [1] effect on optical elements like 3D printed lenses, using Nanoimprint
lithography [2] can be an advantageous combination and is potentially cheap in the fabrication.
Compared to conventional AR-coatings, AR Moth-Eye structures has a broad-spectrum range.
However, structuring such features on a curved surface lens is rather challenging. In this work, wedescribe an effective and simple method for lens fabrication using 3D printing and also surface
patterning of the lens via soft UV Nano Imprint Lithography (UV-NIL) [3].
A precision Stratasys PolyjetTM printer [4] Objet500 was used for 3D printing of a lens core part,which produces smooth and accurate parts with microscopic layer resolution and accuracy down
to 16 µm. During the fabrication process, a liquid photopolymer is jetted onto the build tray, andtiny droplets are instantly cured by UV light (a process similar to inkjet printing can be seen infigure 1. Fine layers are accumulated on the build tray to create a precise 3D model of the lens.
Figure 2 shows a general 3D model of a plano-convex lens shape with a diameter of 54 mm andheight of 6 mm was printed out of a standard transparent UV curable acrylic polymer.
The 3D printed lens was post-processed by structuring nanofeatures using nanoimprint lithography.
A flexible stamp, exhibiting AR Moth-Eye structures, is used to achieve a conformal contact withthe surface to perform an imprint on both front and backside simultaneously. Process feasibility
has been investigated on several 3D objects with curvature in one or more direction. Figure 3 andFigure 4 shows the photographs of the printed lens with and without AR Moth-Eye structures.
Atomic Force Microscopy measurements at different positions on the 3D lens proves thereplication fidelity of the imprinted nanostructures. The potential of this simple and effective
process for nanostructuring of 3D-printed lens using UV-NIL will be presented.
The Austrian Federal Ministry for Transport, Innovation and Technology in the multiLINK projectand Minaelm (Eurostars-2 CoD 6 2016, 859127) project are gratefully acknowledged.
References:[1]E. A. Favret und N. O. Fuentes, Functional Properties of Bio-inspired Surfaces:
Characterization and Technological Applica-tions. World Scientific, 2009.
[2]
H. Schift, Nanoimprint lithography, J Vac Sci Technol B 26 (2008) 458.
[3]
T. Köpplmayr, L. Häusler, I. Bergmair, und M. Mühlberger, „Nanoimprint Lithography on
curved surfaces prepared by fused deposition modelling“, Surf. Topogr. Metrol. Prop., Bd. 3, Nr.
2, S. 024003, Juni 2015.
[4]
Stratasys PolyjetTM, http://www.stratasys.com/polyjet-technology

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:Figure 1. 3D printing process illustration for lensfabrication with PolyjetTM

Figure 2. 3D model of a Plano-convex lenswith a diameter of 54 mm and 6 mm height.

Figure 3. AR-Moth-Eye structure demonstrated on a Figure 4. Photographs of 3D printed lens
3D printed lens. The front and backside of the lens is before post processing without AR-Moth
imprinted with AR-Moth Eyes. The homogeneous Eyes structures.
imprint and coverage is shown by illuminating at avery flat angle of incidence.