With the rapid expansion of the Internet of Things (IoT), secure authentication has become paramount for safeguarding the digital ecosystem against spoofing attacks and privacy breaches. Optical and acoustic modalities currently dominate biometric authentication; however, they remain inherently vulnerable to environmental interference. Here, we report ultrathin (<50 nm), substrate-free gold nanoplatelet skins that conform intimately to finger-knuckle wrinkles, enabling dynamic and nontransferable wearable authentication. Unlike light- or sound-based systems, these nanocrystal skins generate unique resistive signatures that are insensitive to optical and acoustic perturbations. Fabricated from additive-free, polystyrene-capped gold nanoplatelets, the conformal films establish gapless skin-electronic interfaces that replicate knuckle microtopography with high fidelity. This intimate coupling is the key to converting bending-release motions into finger-specific electrical signatures that are unattainable with the corresponding substrate-supported, nonconformal system. Integrated with a deep-learning framework, the two-finger nanoplatelet skin achieves near-perfect authentication accuracy. Our findings indicate that substrate-free nanocrystal skins could enable next-generation wearable biometric authentication, advancing hardware-level security for the digital world.

Copper-based catalysts have been widely reported as remarkable candidates in reforming processes; however, they often suffer from poor stability, sintering, and deactivation over extended periods under high-temperature conditions. Hitherto, the information of the mechanism of the Cu precursor that induces the strong metal-support interaction over the Cu-based catalysts, the role of Cu0 and Cu sigma+ that engendered the reforming, and the stabilization of Cu facets remain limited in the literature. Here, we demonstrate that copper-acetate-based catalyst supported on CeO2 (Cu/CeO2(A)) is a promising candidate for glycerol reforming in terms of stability and reforming efficiency compared to sulphate and nitrate-based Cu/CeO2 catalysts. Through a series of characterization analyses (H2-TPR, H2-TPD, XPS, N2O, HRTEM, Raman spectroscopy, in-situ DRIFTS, and variabletemperature PXRD), the presence of Cu delta+ species in the Cu/CeO2 were found to be the main active sites for promoting the reforming and CO activation. Whereas the Cu0 and oxygen vacancies of CeO2 were to aid in facilitating the glycerol decomposition. Moreover, the in-situ synchrotron-FTIR microspectroscopy further shows that the ratio of Bronsted: Lewis acidic active sites ratio of Cu/CeO2(A) (in high spatial-resolution mode) remained stable between 0.17 and 0.18, for both physisorbed and chemisorbed, indicating that the main acidic sites promoting the glycerol dissociative and adsorption were on the LS sites. Notably, a remarkable performance of 95.1 % of glycerol conversion and 80.8 vol.% H2 production were obtained under the reaction condition of Cu species loading = 10 wt.%, reaction temperature 600 degrees C, glycerol concentration = 10 wt.%, and WHSV =1.953 h- 1.

Metasurfaces exhibit excellent performance in the regulation of optical field parameters, such as phase, amplitude, and polarization, by using nanounit structures. The characteristics of metasurface miniaturization and its combination with advanced semiconductor processes have attracted significant attention, and their design and applications have become the focus of researchers recently. The design of traditional metasurfaces often requires professional designers. Consequently, design work has become difficult and time-consuming with the increase in the complexity of metasurface design. The introduction of artificial intelligence (AI) in metasurface design work has resulted in its rapid development and simplification. Furthermore, metasurfaces have begun to play the role of hidden layers in optical neural networks, and their intelligent properties are gradually being identified. Based on the introduction of the metasurface control mechanism, this paper reviews its intelligent designs and progress. Additionally, the feasibility, necessity, and broad prospects of the combination of AI with metasurfaces are clarified.

Although two-dimensional (2D) materials have grown into an extended family that accommodates hundreds of members and have demonstrated promising advantages in many fields, their practical applications are still hindered by the lack of scalable high-yield production of monolayer products. Here, we show that scalable production of monolayer nanosheets can be achieved by a facile ball-milling exfoliation method with the assistance of viscous polyethyleneimine (PEI) liquid. As a demonstration, graphite is effectively exfoliated into graphene nanosheets, achieving a high monolayer percentage of 97.9% at a yield of 78.3%. The universality of this technique is also proven by successfully exfoliating other types of representative layered materials with different structures, such as carbon nitride, covalent organic framework, zeolitic imidazolate framework and hexagonal boron nitride. This scalable exfoliation technique for monolayer nanosheets could catalyze the synthesis and industrialization of 2D nanosheet materials.

Digital microfluidics, which relies on the movement of drops, is relatively immune to clogging problems, making it suited for micro-reactor applications. Here, graphene oxide paper of 100 μm thickness, fabricated by blade coating sedimented dispersions onto roughened substrates, followed by drying and mechanical exfoliation, was found to be relatively free of cracks and curling. It also exhibited high wettability and elasto-capillary characteristics. Possessing low enough stiffness, it could rapidly and totally self-wrap water drops of 20 μL volume placed 2 mm from its edge when oriented between 0 and 60° to the horizontal. This complete wrapping behavior allowed drops to be translated via movement of the paper over long distances without dislodgement notwithstanding accelerations and decelerations. An amount of 2 drops that were wrapped with separate papers, when collided with each other at speeds up to 0.64 m/s, were found to eschew coalescence. This portends the development of robust digital microfluidic approaches for micro-reactors.

A better understanding of the mechanics of condensation is needed to devise active bioaerosol samplers. Here, dropwise water condensation produced by directing humid air flow perpendicularly on ambient (25 C) and cooled (4 C) copper plate substrates was studied. Numerical data obtained from solving the two-dimensional incompressible Navier-Stokes equations with low Reynolds numbers (=40) showed significant vorticity strength developing at the edges of the copper plate. This resulted in a higher degree of aerosol deposition and an increased likelihood of drop nucleation at the impaction zone. When a drop is already present at the edge, simulations predicted that the high vorticity region shifted to the apexes of drops with concomitant increase in the magnitude of vorticity strength. These results explained the experimentally observed dropwise condensation of larger drops at the edges of the ambient substrate. Analyses of drop size distributions at the center and edges of ambient and cooled substrates showed that drop growth was enhanced by improved condensation on the cooled substrate surface in addition to the flow vorticity effect. Preliminary findings indicate that the recovery of viable aerosolized Escherichia coli from ambient and cooled substrate was found to be invariant, portending its utility for sampling when the electrical power available for cooling is limited.Copyright (c) 2023 American Association for Aerosol Research

The structural characteristics of biological specimens, such as wet proteins and fixed living cells, can be conveniently probed in their host aqueous media using soft X‐rays in the water window region (200–600 eV). Conventional X‐ray detectors in this area exhibit low spatial resolution, have limited sensitivity, and require complex fabrication procedures. Here, many of these limitations are overcome by introducing a direct soft X‐ray detector based on ultrathin tin mono‐sulfide (SnS) nanosheets. The distinguishing characteristic of SnS is its high photon absorption efficiency in the soft X‐ray region. This factor enables the fabricated soft X‐ray detectors to exhibit excellent sensitivity values on the order of 104 μCGyVac−1 cm−2 at peak energies of ≈600 eV. The peak signal is found to be sensitive to the number of stacked SnS layers, with thicker SnS nanosheet assemblies yielding a peak response at higher energies and with peak sensitives of over 2.5 × 104 μCGyVac−1 cm−2 at 1 V. Detailed current–voltage and temporal characteristics of these detectors are also presented. These results showcase the excellent performance of SnS nanosheet‐based soft X‐ray detectors compared to existing direct soft X‐ray detectors, including that of the emerging organic–inorganic perovskite class of materials.

Abstract The authors have requested that this preprint be removed from Research Square.

Highly wetting and nonwetting substrates have been widely used in fogwater collection systems for enhanced water harvesting. In this work, fog harvesting substrates comprising PVC strips of different wetting properties and widths ranging from 1-5 mm were vertically aligned and spaced apart at regular intervals to give the same solid area fraction of 0.8. Evaluation of the water collection efficiencies of the tested configurations revealed that 1 mm wide superhydrophilic strips was the most efficient, achieving double the amount of water harvested compared with 2.8 mm wide strips. This finding was attributed to the low Stokes numbers of the aerosol particle distribution of the fog which tended to result in them being brought by the flow streamlines toward the air gaps between the strips. Stagnant flow regions at the edges of each strip, revealed through potential flow calculations, then caused higher liquid imbibition and impaction there for water harvesting. It was also found that the Cassie nonwetting substrates that originally exhibited contact angles of 161° transformed to Wenzel wetting with zero contact angle within 60 min of fog interception. Optical profilometry revealed no obvious difference in surface roughness between the central region and edges of the strips, indicating that surface morphology was unlikely to be a contributing factor for enhanced water collection at the edges. The findings here indicated that highly wetting vertical strip architectures with narrow widths (1 mm) were favorable over wider strips for water harvesting provided that clogging and re-entrainment were not significant factors.

Size, shape, and chemical properties of nanoparticles are powerful tools to modulate the optical and physicochemical properties of a particle suspension. Despite having many methods to synthesize anisotropic nanoparticles, often there are challenges in terms of controlling the polydispersity, shape, size, or composition of anisotropic nanoparticles. This work has been inspired by the potential for developing a unique pathway to make different shaped monodispersed anisotropic nano- and microparticles with large flexibility in material choice. Compared to existing methods, this state-of-the-art nanolithographic method is fast, easy to prototype, and much simple in terms of its mechanical requirement. We show that this technique has been efficiently used to make a variety of anisotropic nano- and microparticles of different shapes, such as triangular prisms, ovals, disks, flowers, and stairs following the same pathway, at the same time showing the potential of being flexible with respect to the composition of the particles. The thermal scanning probe lithographic method in combination with dry reactive ion etching was used to make two-dimensional and three-dimensional templates for the fabrication of anisotropic nano- and microparticles. Deposition of different metal/metal oxides by the electron-beam evaporation method onto these templates allowed us to fabricate a range of nanomaterials according to the required functionality in potential applications. The particles were characterized by atomic force microscopy, He-ion microscopy, scanning electron microscopy, and dynamic light scattering to ensure that the developed method is reproducible, flexible, and robust in choosing the shapes for making monodispersed anisotropic nanoparticles with great control over shape and size.

Plasmonic color filters based on the hexagonal arrangement of coaxial hole array in aluminum have been demonstrated as a promising candidate for color filter development due to polarization and incident angle insensitivity. They also comprise a single nanometer thick metal film, demonstrate good line width, CMOS compatibility, and fine color tunability. However, the low transmittance of the coaxial hole array based filters limits their use in potential applications such as image sensors and displays. This paper introduces a new method to increase transmittance in coaxial hole array based filters by tuning localized surface plasmons and surface plasmon polaritons. In this method, coaxial holes of small diameters are filled along with a large size coaxial hole array to form a combined filter geometry with optimized parameters in aluminum film using computational techniques. The simulation results will have potential applications in CMOS image sensors, submicron pixel development, microdisplays, and liquid crystal over silicon devices.

The current commercially available glucagon formulations for the treatment of severe hypoglycemia must be reconstituted immediately prior to use, owing to the susceptibility of glucagon to fibrillation and aggregation in an aqueous solution. This results in the inconvenience of handling, misuse, and wastage of this drug. To address these issues, we synthesized a glycosylated glucagon analogue in which the 25th residue (Trp) was replaced with a cysteine (Cys) and a Br-disialyloligosaccharide was conjugated at the Cys thiol moiety. The resulting analogue, glycoglucagon, is a highly potent full agonist at the glucagon receptor. Importantly, glycoglucagon exhibits markedly reduced propensity for fibrillation and enhanced thermal and metabolic stability. This novel analogue is thus a valuable lead for producing stable liquid glucagon formulations that will improve patient compliance and minimize wastage.

Automotive Shredder Residue (ASR), a waste when metals are mostly removed from end-of-life vehicles, has constituents similar to municipal solid waste (MSW) consisting of plastics, rubber, textiles, and some metals. The processing of ASR is a challenge due to its heterogeneous nature, making feeding to a reactor difficult. In this work, a new procedure of ASR pretreatment is proposed to bring particulate nature in the sample for easier feeding during pyrolysis. The thermal breakdown characteristics of the pretreated ASR solids under slow pyrolysis conditions were assessed in a thermogravimetric analyser following the International Confederation for Thermal Analysis and Calorimetry (ICTAC) kinetics committee recommendations. The effect of particle sizes and heating rates were studied at temperatures up to 800 °C at different heating rates of 2, 5, and 10 °C/min for three particle sizes, 38–63 µm, 63–90 µm, and 90–106 µm, and the kinetic data were derived. The volatiles emitted during pyrolysis were characterized by Diffuse Reflectance Infrared Spectroscopy (DRIFTS). We also developed an algorithm for the selection of heating rate during the pyrolysis of the pretreated ASR. The DRIFTS results, kinetic data, and heating rate for the selected particle sizes are useful for the development of a pyrolysis process for pretreated ASR.

The use of superhydrophilic surfaces for superwetting applications can be hampered by their wetting degradation over time. In this work, superhydrophilic surfaces were fabricated by graphene oxide (GO) deposition on roughened polyvinyl chloride (PVC) substrates. These surfaces were found to exhibit zero contact angle when enhanced green fluorescent protein (EGFP) was deposited on the surface immediately after GO was applied. However, when the GO-coated substrate was stored for 3 h, the surface displayed a contact angle of 54.. The main contact line spreading of the EGFP drop was more easily discernible using normal (500 lx, low glare and shadow free) lighting than with blue LED lighting in the dark. The average radius of the spreading main contact line was found to follow a power-law relationship that increased at a faster rate with higher relative humidity. Confocal imaging revealed rings of EGFP deposition following superwetting that is attributable to pinning around the islands of GO accumulation. Substrate superhydrophilic and superwetting properties can be preserved by adequate control of relative humidity. Relative humidity of 80 % was easily maintained for 150 min by incorporating a 20 mu L water drop in a sealed 240-mL container.

The CMY colour camera is different from the RGB counterpart where the subtractive colours cyan, magenta and yellow are used. The CMY camera performs better than an RGB camera in low light conditions. However, conventional CMY colour filter technology made of pigments and dyes are limited in performance for next generation image sensors with submicron pixel sizes. This is because the conventional CMY filters cannot be fabricated in nanoscale as they use their absorption properties to subtract colours. This paper presents a CMOS compatible nanoscale thick CMY colour mosaic made of Al-TiO2-Al nanorods forming a total number of 0.82 million colour filter pixels with each filter pixel size of 4.4 mu m arranged in a CMYM pattern. The colour mosaic was then integrated on a MT9P031 image sensor to make a CMY camera and colour imaging is demonstrated using a 12 colour Macbeth chart. The developed technology will have applications in astronomy, low exposure time imaging in biology, and photography.

We demonstrate a highly sensitive tungsten diselenide (WSe2) field-effect transistor (FET) biosensor for label-free detection of early stage prostate cancer. We modified the FET channel by attaching the monoclonal antibody of prostate specific antigen (anti-PSA) through a multi-step process, followed by bovine serum albumin treatment, which ensures specific binding between anti-PSA and PSA. Our FET biosensor has a detection limit of 10 fg ml−1 PSA, the lowest concentration detected so far by any FET sensor. At this detection limit, the sub-threshold swing is 235mV dec−1 ; and the drain current ( Id ) in the FET increases by 70% compared to that in a pristine device. The FET sensor exhibits linear change in threshold voltage ( Vth ) and drain current ( Id ) over the detection range of 10 fg ml−1 –1 ng ml−1 PSA. Our demonstrated ultra-sensitive and fast WSe2 FET biosensors are promising for point-of-care diagnostics applications.

Tissues, which consist of groups of closely packed cell arrays, are essentially sheet-like biosynthesis plants. In tissues, individual cells are discrete microreactors working under highly viscous and confined environments. Herein, soft polystyrene-encased nanoframe (PEN) reactor arrays, as analogous nanoscale "sheet-like chemosynthesis plants", for the controlled synthesis of novel nanocrystals, are reported. Although the soft polystyrene (PS) is only 3 nm thick, it is elastic, robust, and permeable to aqueous solutes, while significantly slowing down their diffusion. PEN-associated palladium (Pd) crystallization follows a diffusion-controlled zero-order kinetics rather than a reaction-controlled first-order kinetics in bulk solution. Each individual PEN reactor has a volume in the zeptoliter range, which offers a unique confined environment, enabling a directional inward crystallization, in contrast to the conventional outward nucleation/growth that occurs in an unconfined bulk solution. This strategy makes it possible to generate a set of mono-, bi-, and trimetallic, and even semiconductor nanocrystals with tunable interior structures, which are difficult to achieve with normal systems based on bulk solutions.

Surface patterning of liquid metals (LMs) is a key processing step for LM-based functional systems. Current patterning methods are substrate specific and largely suffer from undesired imperfections-restricting their widespread applications. Inspired by the universal catechol adhesion chemistry observed in nature, LM inks stabilized by the assembly of a naturally abundant polyphenol, tannic acid, has been developed. The intrinsic adhesive properties of tannic acid containing multiple catechol/gallol groups, allow the inks to be applied to a variety of substrates ranging from flexible to rigid, metallic to plastics and flat to curved, even using a ballpoint pen. This method can be further extended from hand-written texts to complex conductive patterns using an automated setup. In addition, capacitive touch and hazardous heavy metal ion sensors have been patterned, leveraging from the synergistic combination of polyphenols and LMs. Overall, this strategy provides a unique platform to manipulate LMs from hand-written pattern to complex designs onto the substrate of choice, that has remained challenging to achieve otherwise.

This paper presents a novel technique to combine a plasmonic nanohole array with a dielectric multilayer to make narrow bandpass filters for multispectral imaging at near IR wavelengths.

In this work, the deposition of graphene oxide (GO) on roughened polyvinyl chloride (PVC) surfaces revealed contact angle changes from 16 degrees to zero within 3 s when a 50 mu L water drop was dispensed on them. When the water drop was dispensed 180 min after the surface was prepared, the contact angle changed from 32 degrees to 4 degrees after 35 s. Such time-dependent wetting transition was however not observed with GO deposited on glass nor on unroughened PVC surfaces. A mechanistic explanation for the observed temporal evolution of wetting properties was provided. Optical profilometry scans conducted provided insights on the effect of surface roughness on GO deposition characteristics after evaporation of the GO solution off the substrate surface. The substrate roughness and evaporation dependent temporal wetting transitions of graphene oxide (GO) coating found here is essential in various sensing, transporting, harvesting and actuating applications.