1 3 Microsyst Technol DOI 10.1007/s00542-017-3468-8 TECHNICAL PAPER UV-NIL replication of microlens arrays on flexible fluoropolymer substrates Dalius Jucius 1 · Algirdas Lazauskas 1 · Viktoras Grigaliu ¯nas 1 · Brigita Abakevic ˇiene ˙ 1 · Saulius Smetona 2 · Sigitas Tamulevic ˇius 1 Received: 31 March 2017 / Accepted: 9 June 2017 © Springer-Verlag GmbH Germany 2017 emitting diodes, liquid crystal displays, CCD cameras, con- focal microscopy, coupling of light from optical fibers etc. (Galeotti et al. 2013; Wu et al. 2014; Zaboub et al. 2016). Properly designed microlenses and microlens arrays can significantly increase efficiency of optical devices (Myers et al. 2012; Yang 2009) and are expected to play a major role in miniature optical systems in the future. Growing demand has stimulated development of various fabrication techniques suitable for the realization of high performance microlenses. Microlens arrays made of glass have been studied for a relatively long time compared to those made in other mate- rials (Ottevaere et al. 2006; Zappe 2012). Conventional method used for the production of glass microlens arrays for more than three decades is based on photolithography, photoresist thermal reflow and reactive ion etching (Savan- der 1994). The other techniques include focused ion beam milling, laser ablation combined with thermal treatment, and compression molding of optical quality glass at high temperatures (Delgado et al. 2016; Firestone and Yi 2005; Langridge et al. 2014). Fused silica and other SiO 2 -based glasses are highly transparent, stable and inert. Microlenses made of these materials exhibit a high structural quality as well as excellent optical and thermal properties. On the other hand, fabrication of glass microlens arrays is a chal- lenging process consisting of several expensive and criti- cal technological steps, especially in applications requiring large patterned surfaces. Polymers are good substitute for glasses in making micro-optical components, including microlenses, due to their low cost, wide diversity of properties and efficient production process (Ottevaere et al. 2006). In most cases above mentioned advantages outweigh disadvantages of plastic optical components e.g. lower chemical and weath- ering resistance as well as mechanical strength, greater Abstract This paper describes application of UV-NIL technique for the fabrication of hexagonal OrmoComp microlens arrays on flexible fluoropolymer substrates hav- ing exceptional chemical resistance, stability at elevated temperatures and high transmittance in the UV, visible, and infrared regions of the spectrum. Uniform and well-defined patterns of close-packed convex microlenses were formed in OrmoComp layers on H 2 plasma treated FEP and ETFE substrates by UV-NIL replication of the metalized and liq- uid paraffin antiadhesive coated negative OrmoComp rep- licas of the master mold. UV-NIL replication was success- fully performed at 7.1 kPa imprint pressure and 1100 mJ/ cm 2 exposure dose. Optical testing confirmed good uni- formity and strong focusing ability of the replicated micro- lenses across the entire surface of replicas. Fluoropolymer substrates are especially promising for the use in harsh environments as a cheaper and lightweight substitute for quartz and glass. Moreover, flexible substrates enable fur- ther development of the proposed technique for especially efficient roll-to-roll replication. 1 Introduction Over recent years, microlenses with diameters of a few micrometers to a few hundred micrometers have been widely used for variety of applications including light * Dalius Jucius dalius.jucius@ktu.lt 1 Institute of Materials Science, Kaunas University of Technology, Baršausko St. 59, LT-51423 Kaunas, Lithuania 2 Qorvo, 7628 Thorndike Road, Greensboro, NC 27409, USA