Special Issue "Nanoimprint Lithography Technology and Applications"

A special issue of Nanomaterials (ISSN 2079-4991). This special issue belongs to the section "Nanofabrication and Nanomanufacturing".

Deadline for manuscript submissions: closed (25 February 2021).

Special Issue Editor

Dr. Michael Mühlberger
E-Mail Website
Guest Editor
Functional Surfaces and Nanostructures, Profactor GmbH, Steyr-Gleink, Austria
Interests: nanoimprint lithography, additive micro- and nano-manufacturing, applications of nanoimprinting from optics to life sciences

Special Issue Information

Dear Colleagues,

Nanoimprinting and nanoimprint lithography have evolved tremendously since their beginnings in the mid-1990’s, and have had an impact on a wide application field, ranging from optics to life sciences, from organic electronics to photovoltaics. Today, we find nanoimprint processes in research as well as in industry, and the number of applications is growing constantly.

The variety of processes, materials, and applications is huge, and a sign of the enormous flexibility of the process, which allows for many different requirements to be fulfilled. There are processes working on full wafer-scale or even on display panel size or on curved surfaces. There are nanoimprint tools working in a step-and-repeat way and there are roll-to-roll or roll-to-plate processes. The nanoimprint processes can be based on light-curing materials, thermally curing materials, thermoplastic materials or can be material transfer processes like, for example, microcontact printing processes. Nanoimprint materials range from classical resists for pattern transfer processes like reactive ion etching, to permanent materials for optical or biological applications. Along with the different processes and material requirements come different stamp concepts and stamp materials.

All of this makes nanoimprinting a very versatile process and a fascinating and diverse field of R&D.

This Special Issue of Nanomaterials will attempt to cover the most recent advances and the state-of-the-art in the field of nanoimprinting and nanoimprint lithography as far as the processes, tools, materials, and applications are concerned. Contributions ranging from basic research to industrial applications will be considered. Papers dealing with applications addressing societal challenges like climate change are highly welcome.

Dr. Michael Mühlberger
Guest Editor

Manuscript Submission Information

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Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2200 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Nanoimprint lithography and its applications
  • Nanoimprint processes
  • Nanoimprint materials
  • Nanoimprint stamp fabrication
  • Nanoimprint stamp material
  • Nanoimprint equipment
  • Metrology for nanoimprint

Published Papers (10 papers)

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Research

Open AccessArticle
Nanoimprint Replication of Biomimetic, Multilevel Undercut Nanostructures
Nanomaterials 2021, 11(4), 1051; https://doi.org/10.3390/nano11041051 - 20 Apr 2021
Cited by 1 | Viewed by 300
Abstract
The nanoimprint replication of biomimetic nanostructures can be interesting for a wide range of applications. We demonstrate the process chain for Morpho-blue-inspired nanostructures, which are especially challenging for the nanoimprint process, since they consist of multilayer undercut structures, which typically cannot be replicated [...] Read more.
The nanoimprint replication of biomimetic nanostructures can be interesting for a wide range of applications. We demonstrate the process chain for Morpho-blue-inspired nanostructures, which are especially challenging for the nanoimprint process, since they consist of multilayer undercut structures, which typically cannot be replicated using nanoimprint lithography. To achieve this, we used a specially made, proprietary imprint material to firstly allow successful stamp fabrication from an undercut master structure, and secondly to enable UV-based nanoimprinting using the same material. Nanoimprinting was performed on polymer substrates with stamps on polymer backplanes to be compatible with roller-based imprinting processes. We started with single layer undercut structures to finally show that it is possible to successfully replicate a multilayer undercut stamp from a multilayer undercut master and use this stamp to obtain multilayer undercut nanoimprinted samples. Full article
(This article belongs to the Special Issue Nanoimprint Lithography Technology and Applications)
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Open AccessArticle
Mastering of NIL Stamps with Undercut T-Shaped Features from Single Layer to Multilayer Stamps
Nanomaterials 2021, 11(4), 956; https://doi.org/10.3390/nano11040956 - 09 Apr 2021
Cited by 1 | Viewed by 284
Abstract
Biomimetic structures such as structural colors demand a fabrication technology of complex three-dimensional nanostructures on large areas. Nanoimprint lithography (NIL) is capable of large area replication of three-dimensional structures, but the master stamp fabrication is often a bottleneck. We have demonstrated different approaches [...] Read more.
Biomimetic structures such as structural colors demand a fabrication technology of complex three-dimensional nanostructures on large areas. Nanoimprint lithography (NIL) is capable of large area replication of three-dimensional structures, but the master stamp fabrication is often a bottleneck. We have demonstrated different approaches allowing for the generation of sophisticated undercut T-shaped masters for NIL replication. With a layer-stack of phase transition material (PTM) on poly-Si, we have demonstrated the successful fabrication of a single layer undercut T-shaped structure. With a multilayer-stack of silicon oxide on silicon, we have shown the successful fabrication of a multilayer undercut T-shaped structures. For patterning optical lithography, electron beam lithography and nanoimprint lithography have been compared and have yielded structures from 10 µm down to 300 nm. The multilayer undercut T-shaped structures closely resemble the geometry of the surface of a Morpho butterfly, and may be used in future to replicate structural colors on artificial surfaces. Full article
(This article belongs to the Special Issue Nanoimprint Lithography Technology and Applications)
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Open AccessArticle
Novel Concept of Micro Patterned Micro Titer Plates Fabricated via UV-NIL for Automated Neuronal Cell Assay Read-Out
Nanomaterials 2021, 11(4), 902; https://doi.org/10.3390/nano11040902 - 01 Apr 2021
Viewed by 483
Abstract
The UV-nanoimprint lithography(UV-NIL) fabrication of a novel network of micron-sized channels, forming an open channel microfluidic system is described. Details about the complete manufacturing process, from mastering to fabrication in small batches and in high throughput with up to 1200 micro titer plates [...] Read more.
The UV-nanoimprint lithography(UV-NIL) fabrication of a novel network of micron-sized channels, forming an open channel microfluidic system is described. Details about the complete manufacturing process, from mastering to fabrication in small batches and in high throughput with up to 1200 micro titer plates per hour is presented. Deep insight into the evaluation of a suitable UV-curable material, mr-UVCur26SF is given, presenting cytotoxic evaluation, cell compatibility tests and finally a neuronal assay. The results indicate how the given pattern, in combination with the resist, paves the way to faster, cheaper, and more reliable drug screening. Full article
(This article belongs to the Special Issue Nanoimprint Lithography Technology and Applications)
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Open AccessArticle
UV Nanoimprint Lithography: Geometrical Impact on Filling Properties of Nanoscale Patterns
Nanomaterials 2021, 11(3), 822; https://doi.org/10.3390/nano11030822 - 23 Mar 2021
Viewed by 510
Abstract
Ultraviolet (UV) Nanoimprint Lithography (NIL) is a replication method that is well known for its capability to address a wide range of pattern sizes and shapes. It has proven to be an efficient production method for patterning resist layers with features ranging from [...] Read more.
Ultraviolet (UV) Nanoimprint Lithography (NIL) is a replication method that is well known for its capability to address a wide range of pattern sizes and shapes. It has proven to be an efficient production method for patterning resist layers with features ranging from a few hundred micrometers and down to the nanometer range. Best results can be achieved if the fundamental behavior of the imprint resist and the pattern filling are considered by the equipment and process parameters. In particular, the material properties and pattern size and shape play a crucial role. For capillary force-driven filling behavior it is important to understand the influencing parameters and respective failure modes in order to optimize the processes for reliable full wafer manufacturing. In this work, the nanoimprint results obtained for different pattern geometries are compared with respect to pattern quality and residual layer thickness: The comprehensive overview of the relevant process parameters is helpful for setting up NIL processes for different nanostructures with minimum layer thickness. Full article
(This article belongs to the Special Issue Nanoimprint Lithography Technology and Applications)
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Open AccessEditor’s ChoiceArticle
Optical Polymer Waveguides Fabricated by Roll-to-Plate Nanoimprinting Technique
Nanomaterials 2021, 11(3), 724; https://doi.org/10.3390/nano11030724 - 13 Mar 2021
Viewed by 343
Abstract
The paper reports on the properties of UV-curable inorganic-organic hybrid polymer multimode optical channel waveguides fabricated by roll-to-plate (R2P) nanoimprinting. We measured transmission spectra, refractive indices of the applied polymer materials, and optimized the R2P fabrication process. Optical losses of the waveguides were [...] Read more.
The paper reports on the properties of UV-curable inorganic-organic hybrid polymer multimode optical channel waveguides fabricated by roll-to-plate (R2P) nanoimprinting. We measured transmission spectra, refractive indices of the applied polymer materials, and optimized the R2P fabrication process. Optical losses of the waveguides were measured by the cut-back method at wavelengths of 532, 650, 850, 1310, and 1550 nm. The lowest optical losses were measured at 850 nm and the lowest average value was 0.19 dB/cm, and optical losses at 1310 nm were 0.42 dB/cm and 0.25 dB/cm at 650 nm respectively. The study has demonstrated that nanoimprinting has great potential for the implementation of optical polymer waveguides not only for optical interconnection applications. Full article
(This article belongs to the Special Issue Nanoimprint Lithography Technology and Applications)
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Open AccessEditor’s ChoiceArticle
Guiding Chart for Initial Layer Choice with Nanoimprint Lithography
Nanomaterials 2021, 11(3), 710; https://doi.org/10.3390/nano11030710 - 11 Mar 2021
Viewed by 402
Abstract
When nanoimprint serves as a lithography process, it is most attractive for the ability to overcome the typical residual layer remaining without the need for etching. Then, ‘partial cavity filling’ is an efficient strategy to provide a negligible residual layer. However, this strategy [...] Read more.
When nanoimprint serves as a lithography process, it is most attractive for the ability to overcome the typical residual layer remaining without the need for etching. Then, ‘partial cavity filling’ is an efficient strategy to provide a negligible residual layer. However, this strategy requires an adequate choice of the initial layer thickness to work without defects. To promote the application of this strategy we provide a ‘guiding chart’ for initial layer choice. Due to volume conservation of the imprint polymer this guiding chart has to consider the geometric parameters of the stamp, where the polymer fills the cavities only up to a certain height, building a meniscus at its top. Furthermore, defects that may develop during the imprint due to some instability of the polymer within the cavity have to be avoided; with nanoimprint, the main instabilities are caused by van der Waals forces, temperature gradients, and electrostatic fields. Moreover, practical aspects such as a minimum polymer height required for a subsequent etching of the substrate come into play. With periodic stamp structures the guiding chart provided will indicate a window for defect-free processing considering all these limitations. As some of the relevant factors are system-specific, the user has to construct his own guiding chart in praxis, tailor-made to his particular imprint situation. To facilitate this task, all theoretical results required are presented in a graphical form, so that the quantities required can simply be read from these graphs. By means of examples, the implications of the guiding chart with respect to the choice of the initial layer are discussed with typical imprint scenarios, nanoimprint at room temperature, at elevated temperature, and under electrostatic forces. With periodic structures, the guiding chart represents a powerful and straightforward tool to avoid defects in praxis, without in-depth knowledge of the underlying physics. Full article
(This article belongs to the Special Issue Nanoimprint Lithography Technology and Applications)
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Open AccessArticle
Fabrication of High Aspect Ratio Micro-Structures with Superhydrophobic and Oleophobic Properties by Using Large-Area Roll-to-Plate Nanoimprint Lithography
Nanomaterials 2021, 11(2), 339; https://doi.org/10.3390/nano11020339 - 29 Jan 2021
Cited by 1 | Viewed by 685
Abstract
Bio-inspired surfaces with superamphiphobic properties are well known as effective candidates for antifouling technology. However, the limitation of large-area mastering, patterning and pattern collapsing upon physical contact are the bottleneck for practical utilization in marine and medical applications. In this study, a roll-to-plate [...] Read more.
Bio-inspired surfaces with superamphiphobic properties are well known as effective candidates for antifouling technology. However, the limitation of large-area mastering, patterning and pattern collapsing upon physical contact are the bottleneck for practical utilization in marine and medical applications. In this study, a roll-to-plate nanoimprint lithography (R2P NIL) process using Morphotonics’ automated Portis NIL600 tool was used to replicate high aspect ratio (5.0) micro-structures via reusable intermediate flexible stamps that were fabricated from silicon master molds. Two types of Morphotonics’ in-house UV-curable resins were used to replicate a micro-pillar (PIL) and circular rings with eight stripe supporters (C-RESS) micro-structure onto polycarbonate (PC) and polyethylene terephthalate (PET) foil substrates. The pattern quality and surface wettability was compared to a conventional polydimethylsiloxane (PDMS) soft lithography process. It was found that the heights of the R2P NIL replicated PIL and C-RESS patterns deviated less than 6% and 5% from the pattern design, respectively. Moreover, the surface wettability of the imprinted PIL and C-RESS patterns was found to be superhydro- and oleophobic and hydro- and oleophobic, respectively, with good robustness for the C-RESS micro-structure. Therefore, the R2P NIL process is expected to be a promising method to fabricate robust C-RESS micro-structures for large-scale anti-biofouling application. Full article
(This article belongs to the Special Issue Nanoimprint Lithography Technology and Applications)
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Open AccessArticle
Transfer Durability of Line-Patterned Replica Mold Made of High-Hardness UV-Curable Resin
Nanomaterials 2020, 10(10), 1956; https://doi.org/10.3390/nano10101956 - 01 Oct 2020
Cited by 1 | Viewed by 984
Abstract
Ultraviolet nanoimprint lithography (UV-NIL) requires high durability of the mold for the mass production of nanostructures. To evaluate the durability of a line-patterned replica mold made of high-hardness UV curable resin, repetitive transfer and contact angle measurements of the replica mold were carried [...] Read more.
Ultraviolet nanoimprint lithography (UV-NIL) requires high durability of the mold for the mass production of nanostructures. To evaluate the durability of a line-patterned replica mold made of high-hardness UV curable resin, repetitive transfer and contact angle measurements of the replica mold were carried out. In the line patterns, as the contact angle decreases due to repeated transfer, capillary action occurs, and water flows along them. Therefore, it can be said that a mold with a line pattern exhibits an anisotropic contact angle because these values vary depending on the direction of the contact angle measurement. Subsequently, these anisotropic characteristics were investigated. It was determined that it was possible to predict the lifetime of line-and-space molds over repeated transfers. As the transcription was repeated, the contact angle along the line patterns decreased significantly before becoming constant. Moreover, the contact angle across the line pattern decreased slowly while maintaining a high contact angle with respect to the contact angle along the line pattern. The contact angle then decreased linearly from approximately 90°. The mold was found to be macroscopically defect when the values of the contact angle along the line pattern and the contact angle across the line pattern were close. Predicting the mold’s lifetime could potentially lead to a shortened durability evaluation time and the avoidance of pattern defects. Full article
(This article belongs to the Special Issue Nanoimprint Lithography Technology and Applications)
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Open AccessArticle
Plasmon-Assisted Direction- and Polarization-Sensitive Organic Thin-Film Detector
Nanomaterials 2020, 10(9), 1866; https://doi.org/10.3390/nano10091866 - 17 Sep 2020
Cited by 1 | Viewed by 768
Abstract
Utilizing Bragg surface plasmon polaritons (SPPs) on metal nanostructures for the use in optical devices has been intensively investigated in recent years. Here, we demonstrate the integration of nanostructured metal electrodes into an ITO-free thin film bulk heterojunction organic solar cell, by direct [...] Read more.
Utilizing Bragg surface plasmon polaritons (SPPs) on metal nanostructures for the use in optical devices has been intensively investigated in recent years. Here, we demonstrate the integration of nanostructured metal electrodes into an ITO-free thin film bulk heterojunction organic solar cell, by direct fabrication on a nanoimprinted substrate. The nanostructured device shows interesting optical and electrical behavior, depending on angle and polarization of incidence and the side of excitation. Remarkably, for incidence through the top electrode, a dependency on linear polarization and angle of incidence can be observed. We show that these peculiar characteristics can be attributed to the excitation of dispersive and non-dispersive Bragg SPPs on the metal–dielectric interface on the top electrode and compare it with incidence through the bottom electrode. Furthermore, the optical and electrical response can be controlled by the organic photoactive material, the nanostructures, the materials used for the electrodes and the epoxy encapsulation. Our device can be used as a detector, which generates a direct electrical readout and therefore enables the measuring of the angle of incidence of up to 60° or the linear polarization state of light, in a spectral region, which is determined by the active material. Our results could furthermore lead to novel organic Bragg SPP-based sensor for a number of applications. Full article
(This article belongs to the Special Issue Nanoimprint Lithography Technology and Applications)
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Open AccessArticle
Development, Processing and Applications of a UV-Curable Polymer with Surface Active Thiol Groups
Nanomaterials 2020, 10(9), 1829; https://doi.org/10.3390/nano10091829 - 14 Sep 2020
Viewed by 690
Abstract
We present here a novel resist formulation with active thiol groups at the surface. The material is UV curable, and can be patterned at the micro- and nanoscale by UV nanoimprint lithography. The resist formulation development, its processing, patterning and surface characterization are [...] Read more.
We present here a novel resist formulation with active thiol groups at the surface. The material is UV curable, and can be patterned at the micro- and nanoscale by UV nanoimprint lithography. The resist formulation development, its processing, patterning and surface characterization are presented here. In addition, a possible application, including its use to modify the electrical properties of graphene devices is shown. The cured material is highly transparent, intrinsically hydrophilic and can be made more hydrophilic following a UV-ozone or an O2 plasma activation. We evaluated the hydrophilicity of the polymer for different polymer formulations and curing conditions. In addition, a protocol for patterning of the polymer in the micro and nanoscale by nanoimprinting is given and preliminary etching rates together with the polymer selectivity are measured. The main characteristic and unique advantage of the polymer is that it has thiol functional groups at the surface and in the bulk after curing. These groups allow for direct surface modifications with thiol-based chemistry e.g., thiol-ene reactions. We prove the presence of the thiol groups by Raman spectroscopy and perform a thiol-ene reaction to show the potential of the easy “click chemistry”. This opens the way for very straightforward surface chemistry on nanoimprinted polymer samples. Furthermore, we show how the polymer improves the electrical properties of a graphene field effect transistor, allowing for optimal performance at ambient conditions. Full article
(This article belongs to the Special Issue Nanoimprint Lithography Technology and Applications)
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