R2R-UV-nanoimprinting as a powerful mean forlarge-area fabrication of freeform
micro-optical elements
Dieter Nees1, Barbara Stadlober1, Claude Leiner1, Anja Haase1, Ursula Palfinger1,Ladislav Kuna1, Stephan Ruttloff1, Martin Smolka1, Jan Hesse1,Max Sonnleitner2, Christian Sommer1
Joanneum Research Forschungsgesellschaft mbH
Franz-Pichler Straße 30, 8160 Weiz, Austria1
Genspeed Biotech GmbH
Gewerbepark 2, 4261 Rainbach, Austria2
dieter.nees@joanneum.at

R2R-UV-nanoimprinting sets new benchmarks for the fabrication of miniaturized, low-cost andlow-weight freeform micro-optical elements applicable in lighting, display, medical diagnostics,etc. We demonstrate the related process chain, combining optical design, direct laser lithographymastering, S&R- and R2R-UV-imprinting.
Recently, R2R-UV nanoimprinting has proven to be very useful and unrivalled for the largearea fabrication of high-resolution, hierarchical structures at reasonable throughput for therealization of mechanically flexible functional surfaces useable in bionic applications like dragreducing films or transparent conductive electrodes [1], [2].
Here we report on the utilization of UV-NIL for the manufacturing and upscaling of opticalcomponents in lighting and µ-fluidic applications. One key prerequisite for a versatile
deployment of UV-nanoimprinting is the adjustability of the imprint resin towards the targeted
application scenario. It should be tunable in terms of elasticity and surface tension to account foreasy demolding and wettability and it should have low enough viscosity to allow for large-areacoating. For optical polymer components such as freeform micro-lenses or light out-coupling /reflecting structures the tunability of the refractive index and optical dispersion is particularlyimportant.
Another important aspect is the master fabrication and its upscaling to large-area imprint tools.
Here we introduce a Step & Repeat UV-NIL technique allowing for a high-precision nearlystitch-free multiplication of small scale masters onto polymer films resulting in large andflexible imprint stamps that are readily mounted around the imprint roller.
With these ingredients we R2R-fabricated complex freeform µ-optical element (FF-MOE)
designs with small height that enable a tailored redirection of light from discrete LED sources.
These FF-MOEs were used to demonstrate ultra-thin direct lit luminaires with a very
homogenous illumination over an area with a pore-defined shape [3]. Another application offilm based R2R-imprinted FF-MOE was realized for the improved outcoupling of thechemiluminescence signal of in-vitro diagnostic chips for the detection of diverse pathogens.
The biosensor signal was increased by a factor of ~1.7 as tested in a portable read-out device ofa commercial chip testing platform.

Fig. 1. R2R pilot line and rolls with sawtooth-like micro-optical structures for improved outcouplingof the chemiluminescence light.

Reference:[1] M. Leitgeb et al., “Multilength Scale Patterning of Functional Layers by Roll-to-Roll
Ultraviolet-Light Assisted Nanoimprint Lithography”
ACS Nano 10 (5), 4926 (2016)[2] D. Nees et al., “Experiments towards Establishing of Design Rules for R2R-UV-NIL withPolymer Working Shims”
Proc. of SPIE Vol. 9777, 97770D, doi: 10.1117/12.22181 (2016).
[3] P. Hartmann et al., “Roll-to-Roll UV Nanoimprint Lithography for Large-Area Nano- andMicro-Structuring of Flexible Substrates”
LpR 67, p. 50 (2018)