Nanoimprint Research Articles

Defect-insensitive cylindrical surface lattice resonance array and its batch replication for enhanced immunoassay.

Surface lattice resonances (SLR) have been demonstrated to enhance the sensitivity and reduce the full width at half maximum (FWHM) of the plasmonic resonances. However, their widespread application in immunoassays has been hindered by limitations of high structural defect sensitivity and fabrication costs. Here, we design a novel three-layer cylindrical SLR array that exhibits high tolerance against structural defects, which would facilitate straightforward fabrication. By integrating metal evaporation and nanoimprint lithography, we demonstrate the replication of the SLR array with exceptional quality. Theoretical simulations indicate that the resonance dips of these arrays exhibit are not sensitive to various structural defects. The experimental results reveal that the FWHM of these arrays can be as low as 5.1 nm while maintaining robust resonance characteristics. Furthermore, we demonstrated the high spectral sensitivity of the SLR array, which enabled the detection of immunoglobulin G (IgG) at concentrations as low as 609 pg/mL. These findings emphasize the potential of the defect-insensitive SLR array as a highly scalable immunoassay platform with exceptional performance.

Agarose Micro/Nanostructured Surfaces: A Step Toward an Innovative Solution for Platelet Storage Bags

AbstractIn addressing the critical limitations associated with platelet storage, the study investigates an innovative solution aimed at preventing the unwanted activation of platelets within storage bags. This activation is a key factor that currently restricts the shelf life of platelet products to only 72 h, leading to extreme waste production and high costs. Here, highly effective surfaces are identified for minimizing surface‐induced platelet activation. Using thermal nanoimprint lithography (T‐NIL), a new method is demonstrated for patterning reproducible agarose micro/nanostructures (a natural hydrogel with anti‐platelet adhesive properties) including dots, chains, pills, and squares. The agarose (3%) structured surfaces displayed outstanding flexibility and hydrophilic behavior that prevented platelet adhesion as confirmed by confocal microscopy. Importantly, pill‐shaped structures effectively maintained their ability to prevent platelet adhesion, even after a long cell‐contacting duration. Atomic force microscopy indicated that the effectiveness of dampening platelet adherence is determined by the shape, size, height, and aspect ratio of the structures. A model is provided to explain how the different shapes affect wettability and thereby hinder platelet adherence. The developed anti‐adhesive agarose structured surfaces show promise to revolutionize platelet storage, provide vital insights into biomaterials research, and demonstrate the potential of tailored agarose surfaces in biomedical applications.

Nanoimprinting and backside ultraviolet lithography for fabricating metal nanostructures with higher aspect ratio

This paper introduces an innovative approach to increasing the aspect ratio of metal nanostructures fabricated using nanoimprint lithography (NIL). Although conventional NIL and metal lift-off processes can fabricate metal nanostructures, the achievable aspect ratio is often limited by the inherent constraints of NIL. In this study, we demonstrate that for an ultraviolet (UV) transparent substrate, metal nanostructures patterned via NIL can serve as a photomask. A negative-tone photoresist (PR) layer was then deposited on top of the patterned metal nanostructures. By illuminating the substrate from the backside with UV light and subsequently developing the PR, PR structures complementary and self-aligned to the metal layer were obtained. This enabled a second round of metal deposition and lift-off, thereby increasing the height of the metal structures and enhancing the aspect ratio. Experimentally, we demonstrated that this method can improve the aspect ratio from less than 1.0 to as high as 2.1. This paper also addresses the further developments and potential applications of this technique.

Fabrication of Ultrafine L10-FePt-Based Magnetic Patterns Enabled by Single-Step Nanoimprint-Assisted Block Copolymer Self-Assembly.

The bit islands in magnetic patterns play a crucial role in advancing magnetic recording density, but the trade-off issues between miniaturization and scalable production are still challenging. Here we present a two-in-one technique of nanoimprint lithography (NIL)-assisted self-assembly using a specially engineered FePt-containing block copolymer (BCP), offering a simple one-step fabrication for L10-FePt bit-patterned media with high throughput. This method combines top-down NIL with bottom-up self-assembly to precisely control the ultrafine magnetic bits in the nanoscale patterns. The FePt-derived BCPs, designed with an equal atomic ratio of Fe and Pt, ensure the preparation of homogeneously dispersed L10-FePt nanoparticles (NPs). Subsequent BCP pyrolysis results in NPs with enhanced magnetic properties, significantly advancing high-density data storage devices. This strategy offers a novel approach to drive the innovative creation of ordered magnetic metal alloy NPs arrays for practical applications.

Inverse-Designed Polarization-Insensitive Metasurface Holography Fabricated by Nanoimprint Lithography

Inverse-Designed Polarization-Insensitive Metasurface Holography Fabricated by Nanoimprint Lithography

Photocurable Thiol-Ene/Nanocellulose Elastomeric Composites for Bioinspired and Fluorine-Free Superhydrophobic Surfaces.

Artificially prepared superhydrophobic surfaces toward a self-cleaning "lotus effect" and anticontamination performance have become critically important in the past few years. However, most approaches to create the required topology with a hierarchical roughness comprise several manufacturing steps of varying practicality. Moreover, the desired low surface energy is in most cases achieved with fluorinated moieties that are currently criticized due to biological and environmental hazards. In this work, rapidly photocuring but weak thiol-ene resins were reinforced with cellulose nanofibrils (CNFs) to replicate lotus leaves via one-step UV nanoimprint lithography. The CNFs were surface-modified using countercation exchange of carboxyl groups and grafting of thiol and methacrylate functionalities. The formulation methodology resulted in free-flowing, shear-thinning composite resins without surfactants or dispersants. The rheological and photo-cross-linking behavior of the resins, the thermal stability, the mechanical performance, and the hydrophobicity of the cured composites were characterized. Notably, the surface modifications increased the as received fibril diameter (1.9 ± 0.6 nm) by 1.6-2.3 nm and raised the fibril-resin compatibility. The resins underwent rapid polymerization and the high thermal stability of thiol-enes was retained. The methacrylated nanofibrils (10 vol %) significantly strengthened the rubbery network, outperforming the neat thiol-ene polymer in terms of hardness (3.4×), reduced modulus (5.8×), and wear resistance (>100×). Moreover, the surface of lotus-texturized composites was superhydrophobic with a water contact angle of 155°, higher than that of the neat polymer (147°), and was self-cleaning. These CNF composite resins are compatible with fast-cure processes such as 3D printing and roll-to-roll processing, are exempt of fluorine or any other hydrophobization treatment, and are extremely wear-resistant.

Formation of Multiscale Porous Surfaces via Evaporation-Induced Aggregation of Imprinted Nanowires with Highly Viscous Photocurable Materials

AbstractNumerous structures at the nano and microscale manifest distinctive properties with far-reaching implications across diverse fields, including electronics, electricity, medicine, and surface engineering. Established methods such as nanoimprint lithography, photolithography, and self-assembly play crucial roles in the fabrication of nano- and microstructures; however, they exhibit limitations in generating high-aspect-ratio structures when utilizing high-viscosity photocurable resins. In response to this inherent challenge, we propose a highly cost-effective approach facilitating the direct replication of high-aspect-ratio structures, specifically nanowires, through the utilization of anodized aluminum substrates. This study elucidates the streamlined fabrication process for multiscale porous surfaces achieved through the evaporation-induced integration of solid nanowires printed with high-viscosity photocurable resin.

Amorphous to Crystalline Transition in Nanoimprinted Sol-Gel Titanium Oxide Metasurfaces.

Crystalline titanium dioxide (TiO2) (anatase and rutile) possesses a higher refractive index than amorphous TiO2 and near-zero absorption in the visible region, making them an ideal material for visible metasurfaces. However, fabrication limitations hinder their implementation into flat optics. In this work, a wafer-scale manufacturing platform is proposed for crystalline TiO2 metasurfaces. Sol-gel TiO2 is developed as a printable material in which its material phase can be precisely controlled to produce amorphous, anatase, or rutile, depending on the crystallization temperature. Therefore, anatase or rutile metalenses can be fabricated on a wafer scale using thermal nanoimprint lithography and sintering process. The high refractive index of the crystalline TiO2 contributes to the enhanced conversion efficiency of the fabricated metalenses. The fabricated metalenses exhibit diffraction-limited focusing and imaging capabilities, comparable to the theoretically ideal lenses.

Dynamic and Wavelength‐Dependent Optical Transmission Control with Uniform Bending and Recovery of Shape Memory Nanopillars

AbstractIn this paper, the fabrication, characterization, and investigation of the optical properties of high aspect ratio shape memory polymer (SMP) nanopillars are presented. The SMP nanopillars are fabricated using nanoimprint lithography and double‐replication techniques, resulting in well‐defined structures with a height of 1.3 µm and a diameter of 270 nm that can be uniformly bent across a large area. The optical transmission spectra of both straight and bent SMP nanopillars are studied. Experimental measurements, along with finite‐difference time‐domain simulations, reveal significant alterations in the transmission spectra due to the presence of the nanopillars. The SMP nanopillars provide a smart optical power splitting effect, enabling wavelength‐dependent splitting of incident light by controlling the SMP nanopillar bending angle and direction dynamically with temperature. These findings highlight the potential of SMP nanopillars as versatile components for manipulating light in wavelength‐dependent optical devices.

Fabrication and characterization of zinc oxide nanorods-modified electrodes using nanoimprint lithography for electrochemical sensing of heavy metal ions

This paper uses the nanoimprint lithography (NIL) technique to present the fabrication and characterization of Zinc oxide nanorods (ZnONRs)-modified electrodes. Characterization of the resulting electrode involved X–ray diffraction, Field Emission Scanning Electron Microscope and Transmission electron microscopy. The electrode surface was modified with ZnONRs using the NIL technique to increase the sensitivity of the electrochemical sensor for detecting small quantities of heavy metal ions, which remain a major concern due to their toxicity and environmental harm. Electrochemical measurements and sensing performance evaluations were conducted to analyze the electrochemical properties and sensitivity of the ZnONRs - modified electrodes. The results demonstrated increased sensitivity towards cadmium ions present in aqueous solutions, and the limit of detection is found to be 20.88 ± 0.9 µM.

Large-Area Perovskite Nanocrystal Metasurfaces for Direction-Tunable Lasing.

Perovskite nanocrystals (PNCs) are attractive emissive materials for developing compact lasers. However, manipulation of PNC laser directionality has been difficult, which limits their usage in photonic devices that require on-demand tunability. Here we demonstrate PNC metasurface lasers with engineered emission angles. We fabricated millimeter-scale CsPbBr3 PNC metasurfaces using an all-solution-processing technique based on soft nanoimprinting lithography. By designing band-edge photonic modes at the high-symmetry X point of the reciprocal lattice, we achieved four linearly polarized lasing beams along a polar angle of ∼30° under optical pumping. The device architecture further allows tuning of the lasing emission angles to 0° and ∼50°, respectively, by adjusting the PNC thickness to shift other high-symmetry points (Γ and M) to the PNC emission wavelength range. Our laser design strategies offer prospects for applications in directional optical antennas and detectors, 3D laser projection displays, and multichannel visible light communication.

Фотонные кристаллы: оптимизация характеристик и перспективы оптических приложений

Background: Photonic crystals (PCs) have emerged as a new material for light manipulation, providing unprecedented control over light-matter interaction. This unique capacity is due to their periodic dielectric structure, which may produce photonic band gaps that impact photon transmission. Objective: The article summarizes current advances in photonic crystal design and use, focusing on their significance in creating next-generation optical systems. Methods: The article performed a complete literature analysis, concentrating on the most recent PC production and characterization approaches. Innovative techniques like 3D printing, nanoimprint lithography, self-assembly, and advanced computational modelling were studied in depth to optimize their optical characteristics. Results: Recent studies show that PC manufacturing accuracy has increased significantly, allowing for more effective light manipulation and enhanced optical device functioning. Applications such as ultrasensitive sensors, improved optical fibers, and innovative laser designs demonstrate PCs' rising value. Conclusion: The ongoing advancement of photonic crystal technology is laying a solid basis for the next generation of optical devices. These developments improve existing applications and provide opportunities to investigate new functionality in optical and other electromagnetic systems. Incorporating PCs into numerous technical sectors holds the prospect of significant advances in both commercial and scientific fields.

Nanoporous amorphous carbon nanopillars with lightweight, ultrahigh strength, large fracture strain, and high damping capability

Simultaneous achievement of lightweight, ultrahigh strength, large fracture strain, and high damping capability is challenging because some of these mechanical properties are mutually exclusive. Here, we utilize self-assembled polymeric carbon precursor materials in combination with scalable nano-imprinting lithography to produce nanoporous carbon nanopillars. Remarkably, nanoporosity induced via sacrificial template significantly reduces the mass density of amorphous carbon to 0.66 ~ 0.82 g cm−3 while the yield and fracture strengths of nanoporous carbon nanopillars are higher than those of most engineering materials with the similar mass density. Moreover, these nanopillars display both elastic and plastic behavior with large fracture strain. A reversible part of the sp2-to-sp3 transition produces large elastic strain and a high loss factor (up to 0.033) comparable to Ni-Ti shape memory alloys. The irreversible part of the sp2-to-sp3 transition enables plastic deformation, leading to a large fracture strain of up to 35%. These findings are substantiated using simulation studies. None of the existing structural materials exhibit a comparable combination of mass density, strength, deformability, and damping capability. Hence, the results of this study illustrate the potential of both dense and nanoporous amorphous carbon materials as superior structural nanomaterials.

Nondestructive Demolding of Structure-Designable High-Aspect-Ratio Nanoimprint Template.

Demolding is a crucial step in nanoimprint lithography (NIL) for successfully transferring template structures onto resist materials. The process, however, is often hindered by the adhesion and friction between the template and resist, leading to inevitable defects on the replicas and posing challenges in replicating templates with high-aspect-ratio (HAR) structures. Here, we introduce a novel approach using the dissolvable template method to achieve the nondestructive demolding of structure-designable HAR nanoimprint templates. The templates were fabricated by the 3D lithography technology, employing a positive photoresist that can be easily dissolved in alkaline solutions after exposure to ultraviolet (UV) radiation. By implementing this method, we successfully transferred dense arrays of pillars with a minimal diameter of 1.2 μm and a significant aspect ratio of 18, as well as a microlens array diffuser with randomly distributed structural parameters. The dissolvable template method paves the way for stress-free demolding, broadening NIL's application range.

Comparative Analysis of Positive Photoresist and Negative Photoresist in Nanoimprint Lithography Technology

Comparative Analysis of Positive Photoresist and Negative Photoresist in Nanoimprint Lithography Technology

SERS detection of dopamine in artificial cerebrospinal fluid and in Parkinson’s disease-induced mouse cortex using a hybrid ZnO@Ag nanostructured platform

Rapid, direct, and sensitive detection of metabolites or clinically relevant biomarkers in complex biological samples is still challenging. We report a label-free surface-enhanced Raman scattering (SERS)-based approach for highly sensitive detection of dopamine (DA) in artificial cerebrospinal fluid (aCSF) and mouse brain tissue samples. The hybrid SERS-active sensing platform was designed to maximize the hot spot distribution. It encompasses a network of flexible and polymeric nanotrenches and nanogaps fabricated by nanoimprint lithography (NIL) covered by thin films of zinc oxide (ZnO) and silver (Ag) deposited using pulsed laser deposition (PLD) and direct current magnetron sputtering (DC-MS), respectively. The growth of the ZnO and Ag thin films was assessed by scanning electron microscopy (SEM) technique. The proposed SERS substrate benefits from the interlayered semiconductor–metal contribution in SERS enhancement, leading to a versatile sensing platform with improved detection sensitivity through the increased hot spots distribution. Using this strategy, the proposed assay can achieve an ultralow DA determination at the nM level, a short testing time (<30 min), and high signal reproducibility (RSD 11 %). We also assessed the sensing attributes of our in house developed SERS platform to detect DA in spiked aCSF samples, and a limit of detection (LOD) of 10 μM was achieved. Additionally, after in vivo inducing Parkinson’s disease (PD) in mice, relevant biological samples (striatum and cortical brain tissue) were investigated by SERS and ELISA. Given its good stability and accuracy in complex samples, the SERS-ELISA analysis has great potential to be a powerful tool for the reliable detection of DA in remote conditions.

Sculpting the Electronic Nano-Terrain on a Perovskite Film for Efficient Charge Transport.

Nanopatterned halide perovskites have emerged to improve the performance of optoelectronic devices by controlling the crystallographic and optical properties via morphological modification. However, the correlation between the photophysical property and morphology transformation in nanopatterned perovskite films remains elusive, which hinders the rational design of nanopatterned halide perovskites for optoelectronic devices. In this study, we employed nanoimprinting lithography on a perovskite film to exert a precise control over grain growth and manipulate electronic structures at the level of individual grains. Surface-selective fluorescence lifetime imaging microscopy (FLIM) analyzes the spatiotemporally disentangled geometrical variations in carrier recombination rate and band structure modulation according to different pattern morphologies. Consequently, the stereoscopic mechanism of confined grain growth was unveiled, highlighting the quantitative grain size-based parameters that are crucial for nanoscale material engineering. Notably, the pattern-induced reduction of effective charge mass enabled exclusive control over the subdiffusive carrier transport dynamics on perovskite surfaces, ultimately realizing the surface-selective perovskite photodetectors. The implications of this study are expected to provide valuable guidelines, inspiring innovative design protocols for advancing the next-generation optoelectronic technologies.

Oxygen desorption enabled visible light sensing in embossed TiO2 nanogratings fabricated via thermal nanoimprinting

In this work, the fabrication of the nanoimprinted titanium dioxide (TiO2) gratings via thermal nanoimprinting lithography method (T-NIL) and its visible light response are studied. A polydimethylsiloxane (PDMS) primary mould, which in turn made via pattern transfer of micro/nano tracks present in the optical discs is used in T-NIL process. A transparent TiO2 film on a FTO substrate was subjected to pattern transfer from the PDMS mould. The imprinted TiO2 was post annealed to obtain anatase phase. The optical properties and photo response behaviour of plain and nanoimprinted TiO2 films were measured and compared. Raman spectroscopy measurements indicated the surface enhanced Raman scattering in imprinted samples. The imprinted TiO2 showed reduced reflectance compared to plain TiO2 films due to the increased light path length because of multiple reflections leading to in coupling of light. Photo response was observed under visible light illumination conditions, wherein imprinted TiO2 films showed appreciable photocurrent, which is otherwise very minimal in plain TiO2. The visible light photosensing in imprinted TiO2 occur due to the oxygen adsorption-desorption during the post deposition annealing and under illumination respectively. This work makes use of low-cost PDMS primary mould and T-NIL at favourable temperature and pressure conditions with a promising outlook for fabricating imprinted TiO2 with photo sensing ability and adaptability for large area upscaling.

Bioinspired Hierarchical T Structures for Tunable Wettability and Droplet Manipulation by Facile and Scalable Nanoimprinting.

Developing surfaces that effectively repel low-surface-tension liquids with tunable adhesive properties remains a pivotal challenge. Micronano hierarchical re-entrant structures emerge as a promising solution, offering a robust structural defense against liquid penetration, minimizing area fraction, and creating narrow gaps that generate substantial upward Laplace pressure. However, the absence of an efficient, scalable, and tunable construction method has impeded their widespread applications. Here, drawing inspiration from springtail epidermal structures, octopus suckers, and rose petals, we present a scalable manufacturing strategy for artificial micronano hierarchical T-shaped structures. This strategy employs double-transfer UV-curing nanoimprint lithography to form nanostructures on microstructured surfaces, offering high structural tunability. This approach enables precise control over topography, feature size, and arrangement of nano- and microscale sections, resulting in superamphiphobic surfaces that exhibit high contact angles (>150°) and tunable adhesive forces for low-surface-energy liquids. These surfaces can be applied to droplet-based microreactors, programmable droplet-transfer systems, and self-cleaning surfaces suitable for various liquids, particularly those with low surface tension. Remarkably, we have also succeeded in fabricating the hierarchical structures on flexible and transparent substrates. We demonstrate the advantages of this strategy in the fabrication of hierarchical micronanostructures, opening up a wide range of potential applications.

Precursor-Derived Sensing Interdigitated Electrode Microstructures Based on Platinum and Nano Porous Carbon.

Interdigital electrodes were prepared using nanoimprint lithography and piezoelectric inkjet printing. These processes are simpler and more cost-effective than the industrially used electron beam lithography because of their purely mechanical process step. For the investigation of material dependence, platinum as well as carbon electrodes were fabricated. Afterwards electrodes with various line widths and spacings were tested for the application as a chemiresistive sensor for ferrocenyl-methanol and the influence of the gap-width and conductor cross-section on the sensitivity was investigated. The general suitability of the systems for the production of such structures could be confirmed. Structures with a limit of detection (LOD) down to 1.2 μM and 35.9 μM could be produced for carbon and platinum, respectively, as well as a response time of 3.6 s was achieved.