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It is well known that the twin boundary (TB) spacing plays an important role in controlling the strength of twinned metallic nanopillars. One of the reasons attributed to this strengthening behaviour is the force exerted by the TBs on dislocations. Since the TBs exert repulsive force on dislocations and the plasticity in nanopillars is surface controlled, it is interesting to know whether the TB position from the nanowire surface has any effect on the strength of twinned nanopillars. Using atomistic simulations, here we show that the TB position significantly influences the strength of twinned nanopillars. Atomistic simulations have been performed on nanopillar containing one and two TBs and their position is varied within nanopillar from the center to the surface. The results indicate that in nanopillar containing a single TB, the strength is maximum when the TB is located at the center of the nanopillar and it decreases as the TB is shifted towards the nanopillar surface. On the other hand in nanopillar containing two TBs, the maximum strength is observed when the twin boundaries are placed at distance of one fourth or one fifth the pillar size from the surfaces and it decreases when TBs are moved on either side. The present study demonstrates that the mechanical properties of the twinned nanopillars can be controlled by carefully tailoring the position of the TBs within the nanopillars., 13 Pages, 8 Figures, Journal Publication

Proficiency in light reflectance mitigation is the most crucial factor for high photodetector performance. In this respect light trapping mechanism based on nanostructures or microstructures such as nanopillars, nanocones, nanopyramids have emerged as the most promising candidate for reducing overall light reflectance. This could be attributed to its effective large irradiation area, multiple scattering of incident light as well as increased path length of incident rays in these nanostructures. This paper proposes an optical modelling of a GaAs/GaSb material based vertically oriented core-shell cone topped octagonal shaped nanopillar structure with periodical trapezoidal nanotexturization over it to be deployed over a circular planar detector’s surface of radius 50um. The geometrical analytical investigation of the proposed model exhibits a 0.999 overall absorbance and 0.995A/W photoresponsivity along with 87% EQE at 1um operating wavelength.

The degeneration or loss of skeletal muscles, which can be caused by traumatic injury or disease, impacts most aspects of human activity. Among various techniques reported to regenerate skeletal muscle tissue, controlling the external cellular environment has been proven effective in guiding muscle differentiation. In this study, we report a nano-sized graphene oxide (sGO)-modified nanopillars on microgroove hybrid polymer array (NMPA) that effectively controls skeletal muscle cell differentiation. sGO-coated NMPA (sG-NMPA) were first fabricated by sequential laser interference lithography and microcontact printing methods. To compensate for the low adhesion property of polydimethylsiloxane (PDMS) used in this study, graphene oxide (GO), a proven cytophilic nanomaterial, was further modified. Among various sizes of GO, sGO (

The demand for ever-smaller devices increases with the development of the semiconductor industry. High-resolution patterning based on lithography is significant to fabricate ultra-small nanostructures in various nanodevices. With the minimization of feature size down to nanometric scale, it is challenging to reliably define ultra-small features and structures through lithographic approaches. The ultra-small resist structures defined by lithography approaches usually suffer from mechanical instability behaviors during the development and drying process. The stable mechanical behaviors of lithography-defined resist nanopatterns are the important issue for reliable fabrication. Exploring the mechanical stability of resist patterns is of great importance both scientifically and technologically. Hydrogen silsesquioxane (HSQ) is a high-resolution negative-tone electron-beam resist for sub-10-nm fabrication. But, the ultra-small electron-beam exposed HSQ resist structures usually suffer from collapse and displacement after the development process. Hence, it is essential to understand the stability behavior of HSQ resist nanostructures to reliably fabricate various nanodevices. But, a systematic study of the stability behavior of HSQ is still lacking. To address this issue, we exposed the HSQ nanopillars on different substrates and dried them using different drying methods to probe the factors of critical dimensions, substrate adhesion, and dry methods for reliable HSQ nanopillars fabrication in this work. Through the analysis of experimental data, we found the adhesion dominates the mechanical stability of HSQ nanopillars at the ultra-small scale. By using finite element analysis, we systematically explored the role of the capillary effect in the two main unstable mechanics behaviors (collapse and displacement). To suppress the capillary forces, we optimized the drying process with the use of CO2 supercritical drying. We further provided an effective and facile method through spin-drying in the atmosphere to improve the stability of lithography-defined HSQ pillars.

Highly abundant serum proteins tend to mask the low- and ultralow-abundance proteins, making low-abundance species detection extremely challenging. While traditional highly abundant protein depletion techniques are effective, they suffer from nonspecific binding problems and laborious sample manipulation procedures, and the kinetics of release of current separation systems is inadequately long, causing dilution of the eluted low-abundance protein samples. Here, we introduce an on-chip light-controlled reusable platform for the direct and fast depletion of highly abundant proteins from serum biosamples. Our nanoarrays display fast and highly selective depletion capabilities, up to 99% depletion of highly abundant protein species, with no undesired depletion effects on the concentration of low-abundance protein biomarkers. Displaying an ultrahigh surface area, ∼3400 m2 g-1, alongside a light-triggerable ultrafast release, this platform allows for a high depletion performance, together with high-yield reusability capabilities. Furthermore, this nanostructured light-controlled separation device could easily be integrated with downstream analytical technologies in a single lab-on-a-chip platform.

Applications that require high resolution patterns are numerous, leading to an increasing demand for compact patterning tools and alternative lithographic concepts. For many scientific applications like biosensing or fabrication of metamaterials, or artificial crystals, the achievable resolution and the patterned area of the fabrication process are of main importance. In the field of high-volume manufacturing, there is a need for high-resolution patterning at the industrial exposure wavelength of 13.5 nm. The main industrial application for compact exposure tools is EUV photoresist development and its related process optimization. The overall patterned area is of minor interest. Instead, the focus is placed on the achievable resolution and quality of the intensity distribution used for the patterning tests. The realized EUV dual beamline allows to address both application fields in a single in-lab setup. By operating the source with an argon/xenon (Ar/Xe) gas mixture, a narrowband spectrum with a main wavelength of 10.9 nm is created without the need of spectral filtering. The resulting intensity of up to 2 mW/cm2 in wafer plane allows large area patterning with highest throughput of several mm2/min. Single exposure fields of 2 x 2 mm2 can be stitched together to achieve an overall patterned area of up to several cm² with minimal stitching borders of ~ 1 μm. By inserting a customized multilayer mirror into the beamline, the emission spectrum of the DPP source (operated with pure Xe gas) is in-band filtered to 13.5 nm, thus allowing qualification of industrial photoresists regarding sensitivity, contrast and resolution. The mask-wafer positioning system for the 13.5 nm beamline is designed for maximum rigidity to minimize relative movements between the mask and wafer that would lower the achievable resolution. Multi-field resolution test masks are created in-house and are exposed in a parallel manner to determine the achievable resist resolution in an efficient manner. Transmission mask designs are optimized by a rigorous simulation model. By tuning the pattern geometry on mask, different patterns like contact holes or nanopillars can be created on the wafer, tailored to the required application.

Surface‐Enhanced Raman Spectroscopy In article number 2100640, Yeon Sik Jung, In‐Hwan Lee, and co‐workers demonstrate detection of antibiotics present in aqueous solutions via surface‐enhanced Raman spectroscopy without using any Raman reporter molecules. Using the solvent‐assisted nanotransfer printing technique, ultrafine Ag nanowires are conformally printed on GaN nanopillars to form a metal/semiconductor hybrid structure, which achieves a significant improvement of Raman signals. [Image: see text]

Phononic crystals (PnCs) have attracted much attention due to their great potential for dissipation engineering and propagation manipulation of phonons. Notably, the excellent electrical and mechanical properties of graphene make it a promising material for nanoelectromechanical resonators. Transferring a graphene flake to a prepatterned periodic mechanical structure enables the realization of a PnC with on-chip scale. Here, we demonstrate a nanoelectromechanical periodic array by anchoring a graphene membrane to a 9 × 9 array of standing nanopillars. The device exhibits a quasi-continuous frequency spectrum with resonance modes distributed from ∼120 MHz to ∼980 MHz. Moreover, the resonant frequencies of these modes can be electrically tuned by varying the voltage applied to the gate electrode sitting underneath. Simulations suggest that the observed band-like spectrum provides an experimental evidence for PnC formation. Our architecture has large fabrication flexibility, offering a promising platform for investigations on PnCs with electrical accessibility and tunability.

Broadband achromatic metalens imaging is of great interest in various applications, such as integrated imaging and augmented/virtual reality display. Current methods of achromatic metalenses mainly rely on the compensation of a linear phase dispersion implemented with complex nanostructures. Here, we propose and experimentally demonstrate a polarization-insensitive achromatic metalens (PIA-ML) based on computational wavefront coding. In this method, simple circular or square nanopillars are individually coded such that the focal depths at wavelengths at both ends of the achromatic bandwidth overlap at the designed focal plane, which removes the limitation of requiring a linear phase dispersion. An optimized PIA-ML that works in the full optical communication band from 1300 to 1700nm was obtained using a particle swarm optimization algorithm. Experimental results show that both focusing and imaging of the fabricated metalens are consistent with theoretical predictions within the broadband wavelength range, which provides a new methodology for ultra-broadband achromatic imaging with simple-shaped nanostructures.

Bacterial associated infection is a threat in the medical field. Pseudomonas aeruginosa, one of the major causative agents for nosocomial infection, has developed resistance to almost all the classes of antibiotics. Recently, nanopillar-like structures were identified on the wings of insects such as cicada and dragonfly. Nanopillars both on natural surfaces and those mimicked on artificial surfaces were reported to possess bactericidal activity against a wide range of bacteria. An earlier study reported strain specific variation in the viability of P. aeruginosa on the nanopillar topography of a dragonfly wing under static condition. Here, we report the behavior of P. aeruginosa strains on a dragonfly wing under hydrodynamic conditions. The results of the study indicated that, under hydrodynamic conditions, P. aeruginosa PAO1 was attached in higher numbers to the wing surface than P. aeruginosa ATCC 9027 but killed in lower numbers. The plausible reason was identified to be the masking of nanopillars by the secreted extracellular polysaccharide. The shear rate of 1.0 s−1 showed a relatively higher bactericidal effect among the three tested shear rates.

Metal nanostructures exhibit specific optical characteristics owing to their localized surface plasmon resonance (LSPR) and have been studied for applications in various optical devices. The LSPR property strongly depends on the size and shape of metal nanostructures, thus, plasmonic devices must be designed and fabricated according to their uses. Nanoimprint lithography (NIL) is an effective process for repeatedly fabricating metal nanostructures with controlled sizes and shapes and require optical properties. NIL is a powerful method for mass-producible, low-cost, and large-area fabrication. However, the process lacks flexibility in adjusting the size and shape according to the desirable optical characteristics because the size and shape of metal nanostructures are determined by a single corresponding mold. Here, we conducted a re-shaping process through the air-plasma etching of a polymer’s secondary mold (two-dimensional nanopillar array made of cyclo-olefin polymer (COP)) to modulate the sizes and shapes of nanopillars, then, we controlled the spectral characteristics of the imprinted plasmonic devices. The relationship between the structural change of the mold, which was based on etching time, and the optical characteristics of the corresponding plasmonic device was evaluated through experiments and simulations. According to evaluation results, the diameter of the nanopillar was controlled from 248 to 139 nm due to the etching time and formation of a pit structure. Consequently, the spectral properties changed, and responsivity to the surrounding dielectric environment was improved. Therefore, plasmonic devices based on the re-shaped COP mold exhibited a high responsivity to a refractive index of 906 nm/RIU at a wavelength of 625 nm.

In this paper, a highly sensitive biosensor based on partially immobilized silver nanopillars is proposed. The working frequency of this sensor is in the terahertz band, and the range of the detected refractive index is 1.33 to 1.38. We set air holes of two different sizes on the cross-section of the optical fiber and arranged them into a hexagon. In order to improve the sensitivity, silver nanopillars were immobilized on part of the surface of the fiber cladding. The method for detecting the change of refractive index of the bio-analyte was based on local surface plasmon resonance properties of noble metal. The research recorded valuable data about the values of loss peak and full width at half maximum as well as resonance frequency shift under different setting conditions. The data present the biosensor’s final sensitivity as 1.749 THz/RIU.

A great focus is pondered over the electrochemical anodization method, which offers a less intense synthesis process and results in uniform coverage of Titanium foil with titania nanotubes. After the different structural templates were prepared by different techniques, the surface morphology was done by Field Emission Scanning Electron Microscopy. Thereafter, the PDMS thin coating was done on the template by the spin coating method. To prepare a thick pattern of PDMS, the continuous layering of a dilute solution is done after drying it in an interval of time. After that, the sample was heated in an oven for a few hrs. to prepared molds. Then easily the PDMS mold was peeled off. titania template leaves an impression of the pore on the PDMS substrate and the nano impression of PDMS molds work as a top-electrode application.

Diamond, which was previously believed to exhibit almost no plasticity at room temperature, has been found to exhibit limited plastic behavior by compressing diamond nanopillars and analyzing the resulting dislocation behavior through combined experimental and theoretical studies.

The contribution of water to gecko and gecko-inspired adhesion remains a debate. Here, by investigating the adhesion performances of gecko-inspired nanopillar arrays in humid environments, the func...

The effect of systematically varied mechanical properties and nano- and microscale surface topography on the adhesion and proliferation of human pancreatic cancer cells on fibronectin-functionalized poly(vinyl alcohol) (PVA) hydrogels was studied to understand the impact of these properties of the cell microenvironment on cell attachment and spreading. The mechanical properties of PVA, as assessed by atomic force microscopy (AFM) nanoindentation, were varied by the number of freezing-thawing cycles in the physical cross-linking process used for the generation of the hydrogels. Nano- and micropatterned hydrogel surfaces exposing nanosized PVA pillars and cuboids were fabricated by replicating ordered cylindrical nanopores of anodic aluminum oxide (AAO) and poly(dimethylsiloxane) (PDMS) templates, respectively. Softer PVA hydrogels, functionalized covalently with fibronectin, showed enhanced cell adhesion and proliferation of PaTu 8988t cells in comparison to stiffer hydrogels. In addition, PaTu 8988t cells favored the nanopatterned surfaces over micropatterned and flat hydrogels.

Nanopillar arrays structure deployed over a top photodetector surface exhibits high light coupling efficiency which is attributed to their unique optical and structural properties. The paper presents a proposed GaAs material based periodic pyramidal cut nanopillar structure array model deployed over a 50 µm × 50 µm detector’s surface area. From the geometric analysis of the proposed model structure a maximum 99.8% light absorption has been achieved. Enhanced detector’s performance in terms of 0.75 A/W responsivity, as well as 56.8% external quantum efficiency for a narrow 0.5 µm depletion width, has also been demonstrated.

Background Nanoscale surface roughness has been suggested to have antibacterial and antifouling properties. Several existing models have attempted to explain the antibacterial mechanism of nanoscale rough surfaces without direct observation. Here, conventional and liquid-cell TEM are implemented to observe nanoscale bacteria/surface roughness interaction. The visualization of such interactions enables the inference of possible antibacterial mechanisms. Methods and results Nanotextures are synthesized on biocompatible polymer microparticles (MPs) via plasma etching. Both conventional and liquid-phase transmission electron microscopy observations suggest that these MPs may cause cell lysis via bacterial binding to a single protrusion of the nanotexture. The bacterium/protrusion interaction locally compromises the cell wall, thus causing bacterial death. This study suggests that local mechanical damage and leakage of the cytosol kill the bacteria first, with subsequent degradation of the cell envelope. Conclusion Nanoscale surface roughness may act via a penetrative bactericidal mechanism. This insight suggests that future research may focus on optimizing bacterial binding to individual nanoscale projections in addition to stretching bacteria between nanopillars. Further, antibacterial nanotextures may find use in novel applications employing particles in addition to nanotextures on fibers or films.

Surface micro- and nano-patterning techniques are often employed to enhance the optical interface to single photoluminescent emitters in diamond, but the utility of such surface structuring in applications requiring ensembles of emitters is still open to investigation. Here, we demonstrate scalable and fault-tolerant fabrication of closely packed arrays of fluorescent diamond nanopillars, each hosting its own dense, uniformly bright ensemble of near-surface nitrogen-vacancy centers. We explore the optimal sizes for these structures and realize enhanced spin and photoluminescence properties resulting in a 4.5 times increase in optically detected magnetic resonance sensitivity when compared to unpatterned surfaces. Utilizing the increased measurement sensitivity, we image the mechanical stress tensor in each diamond pillar across the arrays and show that the fabrication process has a negligible impact on in-built stress compared to the unpatterned surface. Our results represent a valuable pathway toward future multimodal and vector-resolved imaging studies, for instance in biological contexts.

Following the recent demonstration of the sensitivity of grazing-incidence X-ray fluorescence to the lateral structure of periodic nano-patterned devices, a computational scheme for the simulation of experimental data is presented. This can be used for the element-selective analysis of 3D atomic distributions in nano-patterned structures., Following the recent demonstration of grazing-incidence X-ray fluorescence (GIXRF)-based characterization of the 3D atomic distribution of different elements and dimensional parameters of periodic nanoscale structures, this work presents a new computational scheme for the simulation of the angular-dependent fluorescence intensities from such periodic 2D and 3D nanoscale structures. The computational scheme is based on the dynamical diffraction theory in many-beam approximation, which allows a semi-analytical solution to the Sherman equation to be derived in a linear-algebraic form. The computational scheme has been used to analyze recently published GIXRF data measured on 2D Si3N4 lamellar gratings, as well as on periodically structured 3D Cr nanopillars. Both the dimensional and structural parameters of these nanostructures have been reconstructed by fitting numerical simulations to the experimental GIXRF data. Obtained results show good agreement with nominal parameters used in the manufacturing of the structures, as well as with reconstructed parameters based on the previously published finite-element-method simulations, in the case of the Si3N4 grating.

Solar harvesting materials or structures, with broadband optical absorption, high-temperature tolerance, and scalable fabrication processes, have attracted much attention for real-life optical appl...

The deformation response of nanoporous gold nanopillars under compression, with varying nanopillar and ligament diameters, is analyzed from a series of molecular dynamics simulations. We have measured the ligament size-dependent elastic modulus of nanoporous nanopillars from the elastic region of stress–strain curves, showing that the elastic modulus at a given solid fraction depends on both the geometrical characteristics of the nanopillars and topology of the ligament structure. We modified the Gibson–Ashby scaling law for nanopillars, to predict the size-dependency found in the simulations. To compare the modified model and the simulation results, we have developed a method to estimate the average number of load-bearing ligaments by employing a unique post-processing technique. The comparison between the scaling law and the simulation results lead us to the conclusion that the elastic response of the nanopillars is predominantly due to the compression of ligaments. The size effect due to the new dimensionality vanishes at larger nanopillar diameter and eventually, the scaling laws resemble the classical laws, which is a function of solid fraction only. Besides the size effect, the need to generate nanoporous nanopillars with different topologies and to ensemble average over the various topologies is discussed.

Heteroepitaxial oxide-based nanocomposite films possessing a variety of functional properties have attracted tremendous research interest. Here, self-assembled vertically aligned nanocomposite (Pr0.5Ba0.5MnO3)1-x:(CeO2)x (x = 0.2 and 0.5) films have been successfully grown on single-crystalline (001) (La,Sr)(Al,Ta)O3 substrates by the pulsed laser deposition technique. Self-assembling behavior of the nanocomposite films and atomic-scale interface structure between Pr0.5Ba0.5MnO3 matrix and CeO2 nanopillars have been investigated by advanced electron microscopy techniques. Two different orientation relationships, (001)[100]Pr0.5Ba0.5MnO3//(001)[1-10]CeO2 and (001)[100]Pr0.5Ba0.5MnO3//(110)[1-10]CeO2, form between Pr0.5Ba0.5MnO3 and CeO2 in the (Pr0.5Ba0.5MnO3)0.8:(CeO2)0.2 film along the film growth direction, which is essentially different from vertically aligned nanocomposite (Pr0.5Ba0.5MnO3)0.5:(CeO2)0.5 films having only (001)[100]Pr0.5Ba0.5MnO3//(001)[1-10]CeO2 orientation relationship. Both coherent and semi-coherent Pr0.5Ba0.5MnO3/CeO2 interface appear in the films. In contrast to semi-coherent interface with regular distribution of interfacial dislocations, interface reconstruction occurs at the coherent Pr0.5Ba0.5MnO3/CeO2 interface. Our findings indicate that epitaxial strain imposed by the concentration of CeO2 in the nanocomposite films affects the self-assembling behavior of the vertically aligned nanocomposite (Pr0.5Ba0.5MnO3)1-x:(CeO2)x films.

In this work, we demonstrate Mn-promoted growth of oxide nanostructures standing on a single-crystal MgAl2O4 substrate after heat treatment. Unlike the short truncated spinel pyramids under Au seeds, the addition of Mn produces spinel nanopillars with lengths of 100–300 nm and pyroxene nanowires up to 10 μm. Compared to Au seeds, Au/Mn seeds have different adsorption behavior and therefore provide an additional mass transfer path along seed surfaces that promotes the growth of nanostructures. This vaporization approach has a potential of being applicable to a wide range of complicated oxides.

The surface morphology of the substrate is one of the decisive factors for ion-desorption efficiency in surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS). Understanding the ...

Nanostructured glass with subwavelength hollow nanopillars of diameters of sub-65 nm was fabricated, showing high optical transmittance and ultralow diffuse reflectance. A simple process involving single-step plasma etching was used on a glass slide coated with a SiO2 sacrificial film. First, SiO2 nanodot structures were formed using plasma-induced anisotropic etching with CF4 plasma. The SiO2 nanodot array then became a secondary etching mask to form hollow nanopillars on the glass. The hollow structures formed at the upper part reaching up to the apex of the nanopillar had a lower solid fraction, while the lower part had a higher fraction. The refractive index (RI) gradually increased from 1.09 (near the value for air) to 1.42 (near the value for glass). Geometry-induced RI gradient enhanced light transmi, while it significantly reduced diffuse reflectance, particularly in the shorter wavelengths, thus suppressing the haziness or milky appearance of the nanostructured glass. Superhydrophilic and antifog...

Nanostructured materials offer the potential to drive future developments and applications of electrochemical devices, but are underutilized because their nanoscale cavities can impose mass transfer limitations that constrain electrochemical signal generation. Here, we report a new signal-generating mechanism that employs a molecular redox capacitor to enable nanostructured electrodes to amplify electrochemical signals even without an enhanced reactant mass transfer. The surface-tethered molecular redox capacitor engages diffusible reactants and products in redox-cycling reactions with the electrode. Such redox-cycling reactions are facilitated by the nanostructure that increases the probabilities of both reactant-electrode and product-redox-capacitor encounters (i.e., the nanoconfinement effect), resulting in substantial signal amplification. Using redox-capacitor-tethered Au nanopillar electrodes, we demonstrate improved sensitivity for measuring pyocyanin (bacterial metabolite). This study paves a new way of using nanostructured materials in electrochemical applications by engineering the reaction pathway within the nanoscale cavities of the materials.

Solar water splitting directly converts solar energy into H2 fuel that is suitable for storage and transport. To achieve a high solar-to-hydrogen (STH) conversion efficiency, elaborate strategies yielding a high photocurrent in a tandem configuration along with sufficient photovoltage should be developed. We demonstrated highly efficient solar water splitting devices based on emerging low-cost Sb2Se3 photocathodes coupled with semitransparent perovskite photovoltaics. A state-of-the-art Sb2Se3 photocathode exhibiting efficient long-wavelength photon harvesting enabled by judicious selection of junction layers was employed as a bottom absorber component. The top semitransparent photovoltaic cells, i.e., parallelized nanopillar perovskites using an anodized aluminum oxide scaffold, allowed the transmittance, photocurrent, and photovoltage to be precisely adjusted by changing the filling level of the perovskite layer in the scaffold. The optimum tandem device, in which similar current values were allocated to the top and bottom cells, achieved an STH conversion efficiency exceeding 10% by efficiently utilizing a broad range of photons at wavelength over 1000 nm.

We fabricated a highly water-repellent quartz nanopillar (NP) structure to investigate the effect of varying the contact angle (CA) by using 10-nm-order gaps and 10-nm-diameter NPs. Gaps from 15 to 30 nm led to CAs of more than 100°, showing hydrophobicity, to a maximum of 105°. The mechanism of repelling water on quartz could be explained by the Cassie-Baxter model with a filling factor. A gap of more than 30 nm fills with water due to capillarity, but a gap of less than 30 nm causes water to be repelled by air. We were able to repeatedly fabricate a quartz NP structure with a controllable gap by using a combination of a bio-template and neutral-beam etching and found this structure to be highly water-repellent. The structure has high durability and optical transparency. As a result, we conclude that it can be used in sensors and lenses on various devices such as cameras and radars.

Bactericidal nanopillar arrays on cicada wings represent a non-toxic antimicrobial technology as they work through physical cell rupture instead of a chemical mechanism. Here, we reported iron-based nanopillar arrays (FeOOH and Fe2O3) that can grow on various substrates by a simple solution method. These surfaces showed good structure-based antimicrobial activity. Even more simply, we have prepared urchin-type FeOOH and Fe2O3 particles, which can be easily coated onto various substrates to create structure-based disinfection surfaces. This work provides a simple and general methodology to apply this killed-by-structure technology for real world uses.

Here, we applied direct laser-induced periodic surface structuring to drive the phase transition of amorphous silicon (a-Si) into nanocrystalline (nc) Si imprinted as regular arrangement of Si nanopillars passivated with a SiO2 layer. By varying the laser beam scanning speed at a fixed pulse energy, we successfully tailored the resulting unique surface morphology of the formed LIPSSs that change from ordered arrangement of conical protrusions to highly uniform surface gratings, where sub-wavelength scale ripples decorate the valleys between near-wavelength scale ridges. Along with the surface morphology, the nc-Si/SiO2 volume ratio can also be controlled via laser processing parameters allowing the tailoring of the optical properties of the produced textured surfaces to achieve anti-reflection performance or partial transmission in the visible spectral range. Diverse hierarchical LIPSSs can be fabricated and replicated over large-scale areas opening a pathway for various applications including optical sensors, nanoscale temperature management, and solar light harvesting. By taking advantage of good wettability, enlarged surface area and remarkable light-trapping characteristics of the produced hierarchical morphologies, we demonstrated the first LIPSS-based surface enhanced fluorescent sensor that allowed the identification of metal cations providing a sub-nM detection limit unachievable by conventional fluorescence measurements in solutions.

In annealing of yttria-stabilized tetragonal zirconia (YSTZ), {011}-specific twins and sub-surface defects are often observed, however their effects on the martensitic phase transformation and deformation behavior of YSTZ have never been investigated. In this work, the roles of twin boundaries (TBs) and pre-existing defects in determining the mechanical properties and subsequent deformation mechanisms of YSTZ nanopillars are studied. Using large-scale molecular dynamics simulations, we show that Young’s modulus and strength of YSTZ decrease with the increase of TB density, but the ductility of YSTZ pillars increases. Phase transformation behavior is found to be correlated to TB density. The sensitivity of mechanical responses of twinned structures to pre-existing defects is also studied. A competitive mechanism between TB-induced phase transformation and void-induced phase transformation is observed. When the diameter of a pre-existing void is smaller than a critical value, only TB-induced phase transformation occurs, which leads to void-insensitive mechanical properties.

A novel technique is demonstrated for the fabrication of silicon nanopillar arrays with high aspect ratios. Our technique leverages on an “antenna effect” present on a chromium (Cr) hard mask during ion-coupled plasma (ICP) etching. Randomly distributed sharp tips around the Cr edge act as antennas that attract etchant ions, which in turn enhance the etching of the Cr edge. This antenna effect leads to a smaller Cr mask size and thus a smaller nanopillar diameter. With optimized SF6 and CHF3 gas flow during ICP etching, we could achieve nanopillar arrays with sub-30 nm diameter, over 20 aspect ratio, and steep sidewall without collapse. The proposed technique may help break the limit of traditional nanopillar array fabrication, and be applied in many areas, such as Surface-Enhanced Raman Scattering (SERS). A series of SERS simulations performed on nanopillar arrays fabricated by this technique show an obvious Raman spectrum intensity enhancement. This enhancement becomes more obvious when the diameter of the nanopillar becomes smaller and the aspect ratio becomes higher, which may be explained by a high light absorption, the lightning-rod effect, and a greater number of free electrons available at the surface due to the higher density of the surface state.

Nanoarrays have been emerging as popular nanostructure platforms to investigate both cell behaviors and biological functions, due to the cell architecture respondence to the biointerface of nanostructures. Herein, we developed a series of aspect ratio tunable nanoarrays through a metal-assisted chemical etching method. Nanoarrays including nanoneedles, nanopillars, and nanoclusters were fabricated with a controllable aspect ratio. We found that nanostructures with a high aspect ratio (>10) induced significant alterations of cell physiological behaviors such as surface attachment, architecture deformation, viability, proliferation and motility. The cells on nanostructures with a high aspect ratio exhibited reorganized actin stress fibers and vimentin filaments, as well as reduced focal adhesion. This research enlarges the diversity of nanostructures on nano-bio interface investigation, provides a new insight for the surface-dependent architecture of cells, and offers unbiased understanding of factors influencing cell physiology.

Integration of highly anisotropic multiferroic thin films on silicon substrates is a critical step towards low-cost devices, especially high-speed and low-power consumption memories. In this work, an oxide–metal vertically aligned nanocomposite (VAN) platform has been used to successfully demonstrate self-assembled multiferroic BaTiO3–Fe (BTO–Fe) nanocomposite films with high structural anisotropy on Si substrates. The effects of various buffer layers on the crystallinity, microstructure, and physical properties of the BTO–Fe films have been explored. With an appropriate buffer layer design, e.g. SrTiO3/TiN bilayer buffer, the epitaxial quality of the BTO matrix and the anisotropy of the Fe nanopillars can be improved greatly, which in turn enhances the physical properties, including the ferromagnetic, ferroelectric, and optical response of the BTO–Fe thin films. This unique combination of properties integrated on Si offers a promising approach in the design of multifunctional nanocomposites for Si-based memories and optical devices.

A Nanopillar based n-CdS/p-CdTe solar cell has been simulated using TCAD device simulator SILVACO. Both the electrodes have been realized on the same plane and at the backside of the device. Detailed study has shown that there is a significant improvement in the extracted parameters of interest for the proposed device in comparison with its equivalent planar p-n junction counterpart. Besides, effective carrier collection by the Nanopillar, has also resulted improvement in the parameters of interests such as maximum power generated, fill factor and conversion efficiency. The parameters of interests have also been improved with the increase of the height of the Nanopillar.

Based on localized surface plasmon resonance (LSPR) enhanced quantum dot (QD) emission in a sandwich assay of “capture PCT antibody/PCT/detection PCT antibody labelled with QD” on a gold nanoarray chip, a fully automated point-of-care (POC) system for quick quantitative analysis of procalcitonin (PCT) for sepsis diagnostics was developed. The core technology of the system is to design and fabricate gold nanostructures that can generate plasmonics at resonant wavelength coincident with excitation wavelength of the fluorescent dyes. Gold nanopillar arrays at the size of 140 nm square and 320 nm pitch were found to be good candidates for the desired dye emission. Gold nanochip fabricated by e-beam lithography or nanoimprinting was integrated into a microfluidic chip, with analyte sampling and bioassay reagent flow controlled by LabVIEW program. To detect QD emission of the bioassay from the chip, a CCD camera and a laser source controlled by LabVIEW were incorporated to form a user-friendly and fully-automated POC system for on-site detection of PCT in clinics. Upon detection, the microfluidic chip is inserted into the POC system, where the processes of blood sample loading, detection antibody recognition, fluorescent dye labelling, fluorescent detection, and data analysis are conducted automatically in the device within 30 min at a test sensitivity of 0.5 ng/ml, which fulfills the clinical needs for diagnosis of sepsis through PCT biomarker.

Absorption of the solar radiation over a wide spectral range is of utmost importance to applications related to the harvesting of solar energy. We numerically demonstrate broadband solar absorption enhancement employing a metamaterial in the form of arrays composed of subwavelength silicon truncated inverted cones, henceforth referred to as light funnel (LF) arrays. We show that the broadband absorption efficiency of an unoptimized LF array is 36% greater compared with an optically-maximized NP array. We show that photon trapping in LF arrays is motivated by proximity effects related to the optical overlap between LFs. We make the distinction between two types of optical overlap: weak overlap in which the coupling between the sparse array modes and the impinging illumination increases with array densification, and strong overlap where the array densification introduces new highly absorbing modes. We show that in nanopillar (NP) arrays the optical intensity inside the NPs decreases upon densification and the overall increase in absorptivity is due to increase in filling ratio (as was also shown by others), while the densification of LF arrays increases the optical intensity inside the individual LF and with the concurrent increase in filling ratio concludes light trapping much superior to that of NP arrays. Light trapping governed by strong proximity effects was not reported to date, and we believe it is an important paradigm for miniaturized lab-on-chip technologies.

Photoelectrochemical water splitting provides a promising strategy for converting solar energy into chemical fuels and has attracted extensive interest. Herein, Bi2MoO6 nanopillars with large surface areas were fabricated on an ITO-coated glass substrate and their photoelectrochemical properties are enhanced through appropriate manipulation of ferroelectric polarization. The Bi2MoO6 photoanode with polarization orientation toward ITO shows an enhanced photocurrent density of 250 μA cm-2 at 1.23 V vs. reversible hydrogen electrode, which is 28% higher than that of pristine Bi2MoO6 nanopillars without macroscopic polarization. The corresponding depolarization electric field benefits the separation of light-excited electron-hole pairs, thus minimizing the recombination of charge carriers and further enhancing the photocurrent current density. Our work offers a new strategy of Bi2MoO6-based photoelectrochemical devices with great potential of application in the conversion of solar energy into chemical fuels.

Inducing new phases in thick films via vertical lattice strain is one of the critical advantages of vertically aligned nanocomposites (VANs). In SrTiO3 (STO), the ground state is ferroelastic, and the ferroelectricity in STO is suppressed by the orthorhombic transition. Here, we explore whether vertical lattice strain in three-dimensional VANs can be used to induce new ferroelectric phases in SrTiO3:MgO (STO:MgO) VAN thin films. The STO:MgO system incorporates ordered, vertically aligned MgO nanopillars into a STO film matrix. Strong lattice coupling between STO and MgO imposes a large lattice strain in the STO film. We have investigated ferroelectricity in the STO phase, existing up to room temperature, using piezoresponse force microscopy, phase field simulation and second harmonic generation. We also serendipitously discovered the formation of metastable TiO nanocores in MgO nanopillars embedded in the STO film matrix. Our results emphasize the design of new phases via vertical epitaxial strain in VAN thin films.

Developing large-area semitransparent solar modules is an essential step in the commercialization of semitransparent photovoltaic technologies. However, it has not yet benefited from the significant scientific advances in the field of perovskite solar cells, probably owing to the difficulties in achieving a highly uniform and large-scale semitransparent light absorber. Herein, a semitransparent solar module comprising anodized aluminum oxide (AAO) template-derived vertically aligned one-dimensional nanopillar CH3NH3PbI3−xClx perovskite is reported, which has a uniform semitransparent absorber with a large area of 40.8 cm2 and exhibits a geometrical fill factor of 95.6%. The AAO scaffold facilitates the formation of a homogeneous perovskite morphology and allows for reduced light reflection. The uniform nanopillar-structured perovskite-based device exhibits enhanced electrical properties owing to the restricted carrier path. Our optimized nanopillar-based semitransparent solar module with nine sub-cells shows a power conversion efficiency of 9.04% and an average visible-light transmittance of 30.2%, clearly exhibiting potential for practical power-generating window applications.

In recent years, nanostructured materials have been deeply investigated for field emission applications. The exploitation of different geometries and morphologies is a key ingredient for the realization of proficient field emitter devices. In this work, we highlight the features of two differently shaped nanostructured materials such as molybdenum disulphide and gallium oxide. We show that Mo S 2 nanoflowers and β-Ga2O3 nanopillars can achieve different field emission performance in terms of maximum current density, turn-on field and field enhancement factor.

Adjusting the morphology and composition of Pd-based materials is a promising strategy to improve their performance for the electrocatalytic formic acid oxidation reaction (FAOR). In this work, we report the preparation of B-doped PdRu nanopillar assemblies (B-PdRu NPAs) by a two-step method using NaBH4 as the boron dopant. On combining the hyper-branched structure and the multi-component synergistic effect, B-PdRu NPAs achieve a high mass activity of 1.09 mA μg-1Pd for the FAOR and retain 73.19% of the initial activity after 500 cycles, which is superior to undoped counterparts. The proposed synthesis strategy provides a simple method for the synthesis of metal-nonmetal nanomaterials with desired composition and design structure for electrocatalytic fields.

We present a coherent spin-torque nano-oscillator (STNO) with spectral linewidths ≤ 10 MHz based on a nanopillar spin-valve device in which an in-plane magnetic free layer (FL) is excited by a combined out-of-plane and in-plane spin-polarized current under external magnetic fields, approximately cancelling the average in-plane dipolar field. The STNO exhibits enhanced nonlinear effective damping (Γeff) in the coherent region, resulting from the torque competition from the two spin polarizers and the spatial variation of the anti-damping effectiveness. This effectively reduces the nonlinear coupling (υ) between the amplitude and the phase fluctuations.

Due to environmental concerns and the increasing drive towards miniaturization of electronic circuits and devices, lead-free ferroelectric films with low leakage current and robust ferroelectric and piezoelectric properties are highly desired. The preferred alternative, BaTiO3, is non-toxic and has ferroelectric properties, but its high leakage current, poor ferroelectricity and piezoelectricity and low Curie temperature of ∼130 °C in thin film form are obstacles for high-temperature practical applications. Here, we report that a negative-pressure-driven enhancement of ferroelectric Curie temperature and effective piezoelectric coefficient are achieved in (111)-oriented BaTiO3 nanocomposite films. The enhanced ferroelectric and piezoelectric properties in the emergent monoclinic BaTiO3 are attributed to the sharp vertical interface and 3D tensile strain that develops upon interspersing stiff and self-assembled vertical Sm2O3 nanopillars through the film thickness. Our work also demonstrates that fabricating oxide films through (111)-oriented epitaxy opens up new avenues for the creation of new phase components and exploration of novel functionalities for developing oxide quantum electronic devices.

One of the most important research topic in optics and photonics is the design of metasurfaces to substitute conventional optical elements that demonstrate unprecedented merits in terms of performance and form factor. In this context, full-space control of metasurfaces that makes it possible to manipulate scattered light in transmission and reflection spaces simultaneously, is proposed as the next-generation scheme in optics, with a potential for applications such as 360° holographic images and novel optical systems. However, previously designed metasurfaces lacked functionality because the desired operation occurs under preconditioned light; therefore, they are difficult to use in real applications. Here, we present a design method that enables polarization-dependent full-space control, in which two independent and arbitrary phase profiles can be addressed to each space. Upon introducing a phase gradient value to realize the critical angle condition, conversion of transmissive into reflective operation is realized. Then, rectangular nanopillars are utilized to facilitate polarization beam splitting with the desired phase. Three samples were fabricated and measured based on the proposed scheme.

Bacterial attachment and proliferation on surfaces threaten human health and negatively impact the medical, food processing, and marine industries. In this study, we synthetically produced bioinspi...