High‐Speed Roll‐to‐Roll Hot Embossing of Micrometer and Sub Micrometer Structures Using Seamless Direct Laser Interference Patterning Treated Sleeves

Rank, Andreas; Lang, Valentin; Lasagni, Andrés Fabían

doi:10.1002/adem.201700201

Cited by 31 publications

(29 citation statements)

References 41 publications

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“…Other authors report similar fluence values for ablation of nickel. 0.36 J/cm 2 was used for DLIP with a laser of 1064 nm wavelength and 10 ps pulse duration 47 . Using longer pulses of 6 ns and 1053 nm wavelength, 2.2 J/cm 2 fluence was selected by 48 .…”

Section: Discussionmentioning

confidence: 99%

Dot-Matrix Hologram Rendering Algorithm and its Validation through Direct Laser Interference Patterning

Tamulevičius¹,

Juodėnas²,

Klinavičius³

et al. 2018

Sci Rep

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The fight against forgery of valuable items demands efficient and reasonably priced solutions. A security tag featuring holographic elements for anti-counterfeiting is one of them. However, the content and colours of a diffraction image that would be seen by an observer are often counterintuitive in the design stage. Here, we propose an original algorithm based on the conical diffraction formalism, which can be used to describe the variations of a diffraction image with respect to all aspects of observation. We validate the output of the algorithm by comparing it to test holograms, which we have produced by employing direct laser interference patterning (DLIP) in electrochemically grown nickel foil. We have employed a motorized femtosecond laser system to micro-machine arrays of 65 µm × 65 µm sized diffraction gratings with a defined orientation and pitch on the order of 1 µm. Based on completed diffraction efficiency measurements, we determined optimal ablation parameters, i.e. 57.4 mJ/cm2 fluence per pulse and 1100 pulses/pixel. Furthermore, we show how accurate the proposed algorithm is through measured diffraction spectra as well as captured diffraction images of test holograms produced using the obtained parameters. Finally, we showcase anti-counterfeiting tag prototypes with complex holographic effects, i.e. colour reconstruction, animation effects, and image multiplexing. The proposed algorithm can severely shorten the time between design and production of a holographic tag, especially when realizing it via a competitive origination technology—DLIP.

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Section: Discussionmentioning

confidence: 99%

Dot-Matrix Hologram Rendering Algorithm and its Validation through Direct Laser Interference Patterning

Tamulevičius¹,

Juodėnas²,

Klinavičius³

et al. 2018

Sci Rep

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show abstract

“…For instance, it serves as an indicator that during the hot embossing process, even the deepest cavities of the sleeve could be filled by the soft polymer. [37,38] In addition, it is demonstrated that the obtained foil has a hierarchical topography with threelevel scales, namely the DLIP-produced grooves and the selforganized LSFL and HSFL. The optical effects of these microand nanostructures are addressed in the following sections.…”

Section: Patterned Polyethylene Terephthalate Foilsmentioning

confidence: 96%

“…[33][34][35][36] In contrast to these methods, direct laser interference patterning (DLIP) is a one-step processing technique able to structure seamless sleeves with feature sizes below 1 μm and at processing speeds already reaching 57 cm 2 min À1 . [37][38][39] In this method, two or more coherent laser beams are overlapped on the sample surface resulting in a periodical intensity distribution within the interference volume. If the absorbed laser energy is high enough, the material is locally removed, producing a repetitive surface pattern with a spatial period in the typical range from 500 nm to 10 μm.…”

Section: Introductionmentioning

confidence: 99%

Toward High‐Throughput Texturing of Polymer Foils for Enhanced Light Trapping in Flexible Perovskite Solar Cells Using Roll‐to‐Roll Hot Embossing

et al. 2020

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A path to further increase the power conversion efficiency of perovskite solar cells is maximizing sunlight absorption using patterned substrates with enhanced light-trapping capabilities. However, to be competitive with traditional solar cells, especially in niche markets, low-cost texturing methods have to be developed. Herein, a roll-to-roll hot embossing method to pattern flexible polyethylene terephthalate (PET) foils is presented as a proof of concept. The cylindrical mold for the embossing process is structured with periodic grooves by picosecond direct laser interference patterning (DLIP). The optical characterization of the textured PET shows a tenfold increase in the haze factor (diffuse-to-global transmittance ratio) compared with flat PET due to the high-intensity diffracted beams. Flexible triple cation perovskite cells deposited onto these patterned substrates show on average an 8% (relative) higher efficiency than similar devices deposited on a reference flat PET substrate. This enhancement can be attributed to the increase in light trapping provided by the textured substrate. Finally, a cost analysis model shows that the additional cost of integrating the proposed hot embossing step into a perovskite solar module manufacturing facility will represent less than 0.35% of the initial fabrication cost.

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“…Mold texturing for injection molding applications requires a high speed and flexibility [24]. Laser patterning has been proven effective for the fast-engraving of highly uniform micro-structured surfaces on a large variety of materials, including steel [25][26][27]. Furthermore, throughputs as high as 1 cm 2 per 10 s have been reported for metals when producing self-organized sub-micron structures [28].…”

Section: Introductionmentioning

confidence: 99%

Functionalization of Plastic Parts by Replication of Variable Pitch Laser-Induced Periodic Surface Structures

et al. 2020

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Surface functionalization of plastic parts has been studied and developed for several applications. However, demand for the development of reliable and profitable manufacturing strategies is still high. Here we develop and characterize a new process chain for the versatile and cost-effective production of sub-micron textured plastic parts using laser ablation. The study includes the generation of different sub-micron structures on the surface of a mold using femtosecond laser ablation and vario-thermal micro-injection molding. The manufactured parts and their surfaces are characterized in consideration of polymer replication and wetting behavior. The results of the static contact angle measurements show that replicated Laser-Induced Periodic Surface Structures (LIPSSs) always increase the hydrophobicity of plastic parts. A maximum contact angle increase of 20% was found by optimizing the manufacturing thermal boundary conditions. The wetting behavior is linked to the transition from a Wenzel to Cassie–Baxter state, and is crucial in optimizing the injection molding cycle time.

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High‐Speed Roll‐to‐Roll Hot Embossing of Micrometer and Sub Micrometer Structures Using Seamless Direct Laser Interference Patterning Treated Sleeves

Cited by 31 publications

References 41 publications

Dot-Matrix Hologram Rendering Algorithm and its Validation through Direct Laser Interference Patterning

Dot-Matrix Hologram Rendering Algorithm and its Validation through Direct Laser Interference Patterning

Toward High‐Throughput Texturing of Polymer Foils for Enhanced Light Trapping in Flexible Perovskite Solar Cells Using Roll‐to‐Roll Hot Embossing

Functionalization of Plastic Parts by Replication of Variable Pitch Laser-Induced Periodic Surface Structures

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