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The scalable synthesis and transfer of large-area graphene underpins the development of nanoscale photonic devices ideal for new applications in a variety of fields, ranging from biotechnology, to wearable sensors for healthcare and motion detection, to quantum transport, communications, and metrology. We report room-temperature zero-bias thermoelectric photodetectors, based on single- and polycrystal graphene grown by chemical vapor deposition (CVD), tunable over the whole terahertz range (0.1-10 THz) by selecting the resonance of an on-chip patterned nanoantenna. Efficient light detection with noise equivalent powers

The EMDrive is a proposed propellantless propulsion concept claiming to be many orders of magnitude more efficient than classical radiation pressure forces. It is based on microwaves, which are injected into a closed tapered cavity, producing a unidirectional thrust with values of at least 1 mN/kW. This was met with high scepticism going against basic conservation laws and classical mechanics. However, several tests and theories appeared in the literature supporting this concept. Measuring a thruster with a significant thermal and mechanical load as well as high electric currents, such as those required to operate a microwave amplifier, can create numerous artefacts that produce false-positive thrust values. After many iterations, we developed an inverted counterbalanced double pendulum thrust balance, where the thruster can be mounted on a bearing below its suspension point to eliminate most thermal drift effects. In addition, the EMDrive was self-powered by a battery-pack to remove undesired interactions due to feedthroughs. We found no thrust values within a wide frequency band including several resonance frequencies and different modes. Our data limit any anomalous thrust to below the force equivalent from classical radiation for a given amount of power. This provides strong limits to all proposed theories and rules out previous test results by at least two orders of magnitude.

The structuring of liquid-liquid and liquid-air interfaces may play an important role in novel microfabrication platforms and biotechnologies, from the spontaneous formation of microfilaments from liquid droplets and the 3D printing of liquids, to the culture of stem cells on emulsions. Understanding the mechanical anisotropy of associated liquid interfaces is essential for the development of such systems. Models of AFM indentation at liquid interfaces, based on the Young-Laplace model, currently do not allow the quantification of interfacial mechanical properties of associated molecular films. This report presents such a model and compares its predictions to interfacial mechanical properties characterised via interfacial shear rheology. An extreme reversal of mechanical anisotropy of liquid-liquid interfaces is observed, upon self-assembly of protein nanosheets, by 5 orders of magnitude. Results indicate that, although interfacial rheology is more sensitive than AFM indentation to the mechanics of molecular films in the low range of interfacial mechanics, AFM indentation allows the quantification of mechanical properties of stiffer molecular films, and remains better adapted to the characterisation of small samples and enables the characterisation of local heterogeneity.

Since the first experimental observation of optical Airy beams, various applications ranging from particle and cell micromanipulation to laser micromachining have exploited their non-diffracting and accelerating properties. The later discovery that Airy beams can self-heal after being blocked by an obstacle further proved their robustness to propagate under scattering and disordered environment. Here, we report the generation of Airy beams on an integrated silicon photonic chip and demonstrate that the on-chip 1D Airy beams preserve the same properties as the 2D beams. The 1D meta-optics used to create the Airy beam has the size of only 3 by 16 microns, at least three orders of magnitude smaller than the conventional optic. The on-chip self-healing beams demonstrated here could potentially enable diffraction-free light routing for on-chip optical networks and high-precision micromanipulation of bio-molecules on an integrated photonic chip.

The theoretical Shockley-Queisser limit of photon-electricity conversion in a conventional p-n junction could be potentially overcome by the bulk photovoltaic effect that uniquely occurs in non-centrosymmetric materials. Using strain-gradient engineering, the flexo-photovoltaic effect, that is, the strain-gradient-induced bulk photovoltaic effect, can be activated in centrosymmetric semiconductors, considerably expanding material choices for future sensing and energy applications. Here we report an experimental demonstration of the flexo-photovoltaic effect in an archetypal two-dimensional material, MoS2, by using a strain-gradient engineering approach based on the structural inhomogeneity and phase transition of a hybrid system consisting of MoS2 and VO2. The experimental bulk photovoltaic coefficient in MoS2 is orders of magnitude higher than that in most non-centrosymmetric materials. Our findings unveil the fundamental relation between the flexo-photovoltaic effect and a strain gradient in low-dimensional materials, which could potentially inspire the exploration of new optoelectronic phenomena in strain-gradient-engineered materials.

Optical tweezers enable the manipulation of micro- and nanodielectric particles through entrapment using a tightly focused laser. Generally, optical trapping of submicron size particles requires high-intensity light in the order of MW/cm2. Here, we demonstrate a technique of stable optical trapping of submicron polymeric beads on nanostructured titanium surfaces (black-Ti) without the use of lasers. Fluorescent polystyrene beads with a diameter d = 20-500 nm were successfully trapped on black-Ti by low-intensity focused illumination of incoherent light at λ = 370 m from a Hg lamp. Light intensity was 5.5 W/cm2, corresponding to a reduced light intensity of 6 orders of magnitude. Upon switching off illumination, trapped particles were released from the illuminated area, indicating that trapping was optically driven and reversible. Such trapping behavior was not observed on nonstructured Ti surfaces or on nanostructured silicon surfaces. Thus, the Ti nanostructures were demonstrated to play a key role.

Ceramic piezoelectric materials have orders of magnitude higher piezoelectric coefficients compared to polymers. However, their brittleness precludes imposition of large strains in mechanical energy harvesting applications. We report here that ice templating affords low bulk modulus lead-free aerogel piezoelectric nanogenerators (PENG) with unprecedented combination of flexibility and high piezoelectric response (voltage and power density). A modified ice templating protocol was used to fabricate piezoelectric nanocomposites of surface modified BaTiO3 (BTO) nanoparticles in crosslinked polyethylene imine. This protocol allowed incorporating a significantly high fraction of BTO particles (up to 83 wt %) in the aerogel, while retaining remarkably high compressibility and elastic recovery up to 80% strain. The output voltage, at an applied compressive force of 20 N (100 kPa), increased with BTO loading and a maximum output voltage of 11.6 V and power density of 7.22 μW/cm2 (49.79 μW/cm3) was obtained for PENG aerogels containing 83 wt% BTO, which is orders of magnitude higher than previously reported values for foam-based piezoelectric energy harvesters. The BTO/PEI PENGs also showed cyclic stability over 900 cycles of deformation. PENGs with higher porosity showed better elastic recovery and piezoelectric properties than lower porosity and higher BTO content aerogels. To the best of our knowledge, this is the first report to demonstrate the piezoelectric properties of high ceramic content aerogels having very high compressibility and elastic recovery.

By continuously varying the structure of graphene oxide paper (PRGP) using Joule heating annealing, we are able to tune its electrical conductivity (σ) and thermal diffusivity (α) in a very wide range: more than three orders of magnitude for σ (186–503009 S/m) and 10-fold for α (8.31 × 10−7 m2/s to 9.31 × 10−6 m2/s). Excellent coherency-linear relationship between σ and α is discovered although they are sustained by different carriers: electrons and phonons. Such coherency exists over two sections: σ > 2 × 104 S/m, and 103

In plasmon-mediated photocatalysis it is of critical importance to differentiate light-induced catalytic reaction rate enhancement channels, which include near-field effects, direct hot carrier injection, and photothermal catalyst heating. In particular, the discrimination of photothermal and hot electron channels is experimentally challenging, and their role is under keen debate. Here we demonstrate using the example of CO oxidation over nanofabricated neat Pd and Au50Pd50 alloy catalysts, how photothermal rate enhancement differs by up to 3 orders of magnitude for the same photon flux, and how this effect is controlled solely by the position of catalyst operation along the light-off curve measured in the dark. This highlights that small fluctuations in reactor temperature or temperature gradients across a sample may dramatically impact global and local photothermal rate enhancement, respectively, and thus control both the balance between different rate enhancement mechanisms and the way strategies to efficiently distinguish between them should be devised.

When dealing with reactions of a liquid reactant and a solid catalyst, macroreactors with vigorous stirring equipment may be dangerous and cause wastage of energy. Reducing the diffusion distance and promoting reactants to reach the catalyst surface for efficient reaction remain the key challenges. Here, inspired by capillary-driven water motion in plants, we propose to implement a self-driven multiplex reaction (SMR) in nanocatalyst-loaded microchannels. Unlike the classical capillary rise, the droplet in SMR has variable pressure difference, leading to tunable flow velocity for controlling the reaction rate without any auxiliary equipment. The SMR in microchannels contributes to an increase in the reaction rate by more than 2 orders of magnitude compared to that in macroreactors. Specifically, this strategy reduces the reaction volume by 170 times, the catalyst usage by about 12 times, and the energy consumption by 50 times. This apparatus with a small volume and less catalyst content promises to provide an efficient strategy for the precise manipulation of chemical reactions.

Development of memory devices with ultimate performance has played a key role in innovation of modern electronics. As a mainstream technology nonvolatile memory devices have manifested high capacity and mechanical reliability, however current major bottlenecks include low extinction ratio and slow operational speed. Although substantial effort has been employed to improve their performance, a typical hundreds of micro- or even milli- second write time remains a few orders of magnitude longer than their volatile counterparts. We have demonstrated nonvolatile, floating-gate memory devices based on van der Waals heterostructures with atomically sharp interfaces between different functional elements, and achieved ultrahigh-speed programming/erasing operations verging on an ultimate theoretical limit of nanoseconds with extinction ratio up to 10^10. This extraordinary performance has allowed new device capabilities such as multi-bit storage, thus opening up unforeseen applications in the realm of modern nanoelectronics and offering future fabrication guidelines for device scale-up., Comment: Preprint version, to be published in Nature Nanotechnology (Submitted on August 16th, 2020)

The availability of portable analytical devices for on-site monitoring and rapid detection of analytes of forensic, environmental, and clinical interest is vital. We report the development of a portable device for the detection of biochemiluminescence relying on silicon photomultiplier (SiPM) technology, called LuminoSiPM, which includes a 3D printed sample holder that can be adapted for both liquid samples and paper-based biosensing. We performed a comparison of analytical performance in terms of detectability with a benchtop luminometer, a portable cooled charge-coupled device (CCD sensor), and smartphone-integrated complementary metal oxide semiconductor (CMOS) sensors. As model systems, we used two luciferase/luciferin systems emitting at different wavelengths using purified protein solutions: the green-emitting P. pyralis mutant Ppy-GR-TS (λmax 550 nm) and the blue-emitting NanoLuc (λmax 460 nm). A limit of detection of 9 femtomoles was obtained for NanoLuc luciferase, about 2 and 3 orders of magnitude lower than that obtained with the portable CCD camera and with the smartphone, respectively. A proof-of-principle forensic application of LuminoSiPM is provided, exploiting an origami chemiluminescent paper-based sensor for acetylcholinesterase inhibitors, showing high potential for this portable low-cost device for on-site applications with adequate sensitivity for detecting low light intensities in critical fields.

Raman optical activity (ROA) is effective for studying the conformational structure and behavior of chiral molecules in aqueous solutions and is advantageous over X-ray crystallography and nuclear magnetic resonance spectroscopy in sample preparation and cost performance. However, ROA signals are inherently minuscule; 3–5 orders of magnitude weaker than spontaneous Raman scattering due to the weak chiral light–matter interaction. Localized surface plasmon resonance on metallic nanoparticles has been employed to enhance ROA signals, but suffers from detrimental spectral artifacts due to its photothermal heat generation and inability to efficiently transfer and enhance optical chirality from the far field to the near field. Here we demonstrate all-dielectric chiral-field-enhanced ROA by devising a silicon nanodisk array and exploiting its dark mode to overcome these limitations. Specifically, we use it with pairs of chemical and biological enantiomers to show >100x enhanced chiral light–molecule interaction with negligible artifacts for ROA measurements., Raman optical activity (ROA) is useful for studying conformational structure and behavior of chiral molecules, but is limited by the weak signals. Here, the authors demonstrate 100x signal enhancement via an all-dielectric approach, using a silicon nanodisk array and exploiting its dark mode.

Electro-optic modulation based on a graphene nanoelectromechanical system (NEMS) with superlubricity is proposed and systematically theoretical investigated. We demonstrate that the superlubricity greatly improve the performance of photoelectric modulators based on graphene NEMS due to its extremely low coefficient of friction. The modulation voltage of graphene NEMS electro-optic modulation with superlubricity can be reduced to 200 mV, which is 1–3 orders of magnitude larger lower than that of the traditional electro-optical modulator, giving rise to a dramatic reduction of the power consumption of the modulator by approximately 3 orders of magnitude. The modulation response speed can reach nanoseconds, which is 4 orders of magnitude higher than the speed of traditional mechanical electro-optic modulation. At the same time, this modulator has a very wide modulation wavelength range and is not sensitive to the angle of incident light. Two-dimensional material devices, incorporated with mechanical modulation and superlubricity, will have important applications in optoelectronics and optical communication.

Since modern propulsion systems are insufficient for large-scale space exploration, a breakthrough in propulsion physics is required. Amongst different concepts, the EMDrive is a proposed device claiming to be more efficient in converting energy into propulsive forces than classical photon momentum exchange. It is based on a microwave resonator inside a tapered cavity. Recently, Taylor suggested using a laser instead of microwaves to boost thrust by many orders of magnitude due to the higher quality factor of optical resonators. His analysis was based on the theory of quantised inertia by McCulloch, who predicted that an asymmetry in mass surrounding the device and/or geometry is responsible for EMDrive-like forces. We put this concept to the test in a number of different configurations using various asymmetrical laser resonators, reflective cavities of different materials and size as well as fiber-optic loops, which were symmetrically and asymmetrically shaped. A dedicated high precision thrust balance was developed to test all these concepts with a sensitivity better than pure photon thrust, which is the force equivalent to the radiation pressure of a laser for the same power that is used to operate each individual devices. In summary, all devices showed no net thrust within our resolution at the Nanonewton range, meaning that any anomalous thrust must be below state-of-the-art propellantless propulsion. This puts strong limits on all proposed theories like quantised inertia by at least 4 orders of magnitude for the laboratory-scale geometries and power levels used with worst case assumptions for the theoretical predictions.

An atomic diffusion model is developed to predict the thickness of intermetallic compounds (IMCs) at the interface of aluminum/magnesium alloys in dissimilar friction stir welding. Both the temperature and the strain rate associated with dislocation density at the checking point are used to determine the diffusion coefficients. The variations of the diffusion coefficients and the thickness of IMCs are quantitatively analyzed at selected characteristic time instants during welding process. It is found that the dislocation density can increase the diffusion coefficient and plays a dominant role in the IMCs formation during the plastic deformation stage. Especially in magnesium alloy and Al12Mg17, the diffusion coefficient is increased by two orders of magnitude or even nearly three orders of magnitude by considering the dislocation density. The temperature is the main influencing factor after the end of plastic deformation. The model is validated by comparing the predicted thickness of IMCs with the experimentally measured results.

Radio frequency (RF) microelectromechanical systems (MEMS) based on Al1-xScxN are replacing AlN-based devices because of their higher achievable bandwidths, suitable for the fifth-generation (5G) mobile network. However, overheating of Al1-xScxN film bulk acoustic resonators (FBARs) used in RF MEMS filters limits power handling and thus the phone's ability to operate in an increasingly congested RF environment while maintaining its maximum data transmission rate. In this work, the ramifications of tailoring of the piezoelectric response and microstructure of Al1-xScxN films on the thermal transport have been studied. The thermal conductivity of Al1-xScxN films (3-8 W m-1 K-1) grown by reactive sputter deposition was found to be orders of magnitude lower than that for c-axis-textured AlN films due to alloying effects. The film thickness dependence of the thermal conductivity suggests that higher frequency FBAR structures may suffer from limited power handling due to exacerbated overheating concerns. The reduction of the abnormally oriented grain (AOG) density was found to have a modest effect on the measured thermal conductivity. However, the use of low AOG density films resulted in lower insertion loss and thus less power dissipated within the resonator, which will lead to an overall enhancement of the device thermal performance.

While ionic flow over graphenic structures creates electromotive potential, there is a need to understand the local carrier density induced in graphene without any electrode-induced Fermi-level pinning. Here, we show the electrolyte-flow induced localized doping in graphene via inspecting its Raman phononic energy. Graphene's Fermi energy level has a logarithmic dependence to the flow velocity over 2 orders of magnitude of velocity (∼100 μm s-1 to 10 mm s-1). A theoretical model of the electric double layer (EDL) during ionic transport is used to correlate the Fermi level of graphene with the flow rate and the electronic structure (HOMO-LUMO levels) of the ionic species. This correlation can allow us to use graphene as a reliable, non-invasive, optical flow-sensor, where the flow rates can be measured at high spatial resolution for several lab-on-a-chip applications.

In this issue of Chem, Hess et al. describe a droplet-based microfluidic platform for the acquisition of transient kinetic data of enzyme-catalyzed reactions. Compared with conventional equipment, their platform reduces assay volumes by up to six orders of magnitude and allows up to 9,000 reactions to be screened per minute.

The review contains information on the properties of phase-change materials (PCM) and the possibilities of their use as the basis of thermal energy storage. Special attention is given to PCMs with a phase transition temperature ranging between 20 and 80°C since such materials can be effectively used to reduce temperature variations in residential and industrial rooms. Thus, the application of PCMs in the construction industry enables one to considerably reduce the power consumption and reduce the environmental impact of industrial facilities. Thermophysical characteristics of the main types of PCMs are presented. The heat balance for a room with walls made of PCM-added materials is estimated. The predictions demonstrate that such structures can stabilize the temperature in practical applications as a result of usage of such materials. The potential of wide application of PCMs as a basis for thermal energy storage is limited due to very low conductivity (less than 1 W/(m K)) specific for these materials. Hence, the option of increasing the material conductivity by adding some carbon nanotubes whose thermal conductivity is four to five orders of magnitude greater than that of the base material is examined. The numerical predictions of the heat-conduction enhancement in a PCM doped with carbon nanotubes and the preliminary experiments indicate that a PCM with approximately 20% carbon nanotubes can enhance the material heat conductivity by two to four times.

Lisää oa-julkaisu, kun saatavilla. A sensitive photoacoustic detection approach employing a silicon cantilever is investigated for power measurement of electromagnetic radiation. The technique which is actuated by pressure waves generated through radiation-induced heat depicts high sensitivity for a considerably large spectral range from 325 nm to 1523 nm. The implemented method shows linear response in the measurement of radiation power from 15 nW to 6 mW demonstrating a dynamic range of almost six orders of magnitude. A numerical model has been developed to analyze and optimize the measurement sensitivity. The model allows studying different dimensions of the cantilever which is one of the key components of the radiation detection process. The numerical results are in good agreement with experimental results. The electromagnetic power detection technique shows future potential for industrial applications and scientific studies.

Understanding electronic and ionic transport across interfaces is crucial for designing high-performance electric devices. The adjustment of work functions is critical for band alignment at the interfaces of metals and semiconductors. However, the electronic structures at the interfaces of metals and mixed conductors, which conduct both electrons and ions, remain poorly understood. This study reveals that a Schottky barrier is present at the interface of the Nb-doped SrTiO3 metal and a LiCoO2 mixed conductor and that the interfacial resistance can be tuned by inserting an electric dipole layer. The interfacial resistance significantly decreased (by more than 5 orders of magnitude) upon the insertion of a 1 nm thick insulating LaAlO3 layer at the interface. We apply these techniques to solid-state lithium batteries and demonstrate that tuning the electronic energy band alignment by interfacial engineering is applicable to the interfaces of metals and mixed conductors. These results highlight the importance of designing positive electrode and current collector interfaces for solid-state lithium batteries with high power density.

Present GaN technology consists primarily of heteroepitaxial, lateral high electron mobility transistors; however, high-power devices would be much more efficiently manufactured with a vertical geometry due to better blocking voltage scaling. This technology has yet to be realized due to the inconsistency of GaN wafer properties. These inconsistencies can be detected with several long-range, non-destructive techniques including Raman spectroscopy, optical profilometry, and photoluminescence mapping. In particular, Raman spectroscopy is an effective tool for determining the carrier concentration of GaN substrates and whether the wafers are uniform or inhomogeneous. In this work, vertical p-i-n GaN diodes are fabricated using both uniform and inhomogeneous wafers determined by using the A1 Raman peak position to monitor carrier concentration. The inhomogeneous samples have regular patterns of varying conductivity as a result of electron-donating defects brought about by changes in crystal stress. By avoiding these defects, we have found that diode performance improves by increasing the +/− 10 V rectification ratio by up to a factor of 5X and reducing the 200 V reverse bias leakage current by several orders of magnitude. Using the higher quality substrates with uniform electron carrier concentrations can improve the rectification ratio by another order of magnitude.

Dual-color photodetection can increase detection accuracy due to the specific information from different wavelengths. Traditional dual-color detectors are based on double optical modules or photovoltage devices, which suffer from huge system weight or low gain. In this Letter, a novel dual-color photodetector with Ge/Graphene/CdS sandwich profile is proposed. While visible and infrared light is mainly absorbed by the CdS and Ge layers, respectively, photoelectrical signals from two wavelengths both conducted by graphene are extracted on time-sequence with different sampling frequencies. Based on a tailored interface process and epitaxy InGaAs instead of bulk Ge layer, the difference in response speed more than 3 orders of magnitude (76 kHz/14 Hz) was realized. Due to the photogating effect, the high gain was obtained for both wavelengths, and a photoresponse enhancement originated from the overlapping of local photogating field is observed. The device provided a new solution for high-gain and CMOS-compatible dual-color photodetection.

Optofluidic biolasers have emerged as promising tools for biomedical analysis due to their strong light-matter interactions and miniaturized size. Recent developments in optofluidic lasers have opened a new Frontier in monitoring biological processes. However, most biolasers require precise recording of the lasing spectrum at the single cavity level, which limits its application in high-throughput applications. Herein, a microdroplet laser array encapsulated with living Escherichia coli was printed on highly reflective mirrors, where laser emission images were employed to reflect the dynamic changes in living organisms. The concept of image-based lasing analysis was proposed by quantifying the integrated pixel intensity of the lasing image from whispering-gallery modes. Finally, dynamic interactions between E. coli and antibiotic drugs were compared under fluorescence and laser emission images. The amplification that occurred during laser generation enabled the quantification of tiny biological changes in the gain medium. Laser imaging presented a significant increase in integrated pixel intensity by 2 orders of magnitude. Our findings demonstrate that image-based lasing analysis is more sensitive to dynamic changes than fluorescence analysis, paving the way for high-throughput on-chip laser analysis of living organisms. Agency for Science, Technology and Research (A*STAR) Nanyang Technological University This research is supported by A*STAR under its AME IRG Grant (project no. A2084c0063). We would like to thank the lab support from Centre of Bio-Devices and Bioinformatics and Internal grant NAP SUG-M4082308.040 from NTU.

Abstract Surface Free Energy (SFE) has become a relevant design parameter to produce materials and devices with controlled wettability. The non-destructive measurement of SFE in nanopatterned super-hydrophobic hard surfaces is a challenge in both research and industry since in most cases time-consuming contact angle measurements are not feasible. In this work, we present a novel nanoindentation based method for the measurement of pull-off adhesive forces by carefully controlling environmental and instrumentation issues. The method is found to measure SFE over five orders of magnitude, covering hydrophilic to super-hydrophobic surfaces, and has been validated with contact angle measurements. Its limitations and shortcomings are critically discussed, with a specific focus on the experimental issues that could affect the reliability and reproducibility of the results. Finally, the potential applications of the newly developed methodology include fast non-destructive mapping of SFE over heterogeneous surfaces with spatially controlled wettability. Graphic abstract

We present a machine learning based surrogate modeling method for predicting spatially resolved 3D crystal orientation evolution of polycrystalline materials under uniaxial tensile loading. Our approach is orders of magnitude faster than the existing crystal plasticity methods enabling the simulation of large volumes that would be otherwise computationally prohibitive. This work is a major step beyond existing ML-based modeling results, which have been limited to either 2D structures or only providing average, rather than local 3D full-field predictions. We demonstrate the speed and accuracy of our surrogate model approach on experimentally collected data from a face-centered cubic copper sample undergoing tensile deformation.

Optical tweezers are widely used in materials assembly1, characterization2, biomechanical force sensing3,4 and the in vivo manipulation of cells5 and organs6. The trapping force has primarily been generated through the refractive index mismatch between a trapped object and its surrounding medium. This poses a fundamental challenge for the optical trapping of low-refractive-index nanoscale objects, including nanoparticles and intracellular organelles. Here, we report a technology that employs a resonance effect to enhance the permittivity and polarizability of nanocrystals, leading to enhanced optical trapping forces by orders of magnitude. This effectively bypasses the requirement of refractive index mismatch at the nanoscale. We show that under resonance conditions, highly doping lanthanide ions in NaYF4 nanocrystals makes the real part of the Clausius–Mossotti factor approach its asymptotic limit, thereby achieving a maximum optical trap stiffness of 0.086 pN μm–1 mW–1 for 23.3-nm-radius low-refractive-index (1.46) nanoparticles, that is, more than 30 times stronger than the reported value for gold nanoparticles of the same size. Our results suggest a new potential of lanthanide doping for the optical control of the refractive index of nanomaterials, developing the optical force tag for the intracellular manipulation of organelles and integrating optical tweezers with temperature sensing and laser cooling7 capabilities. The resonance of highly doping lanthanide ions in NaYF4 nanocrystals enhances the permittivity and polarizability of nanocrystals, leading to enhanced optical trapping forces by orders of magnitude, bypassing the trapping requirement of refractive index mismatch.

Graphene field-effect transistors (GFETs) are suitable building blocks for high-performance electrical biosensors, because graphene inherently exhibits a strong response to charged biomolecules on its surface. However, achieving ultralow limit-of-detection (LoD) is limited by sensor response time and screening effect. Herein, we demonstrate that the detection limit of GFET biosensors can be improved significantly by decorating the uncovered graphene sensor area with carbon dots (CDs). The developed CDs-GFET biosensors used for exosome detection exhibited higher sensitivity, faster response, and three orders of magnitude improvements in the LoD compared with nondecorated GFET biosensors. A LoD down to 100 particles/μL was achieved with CDs-GFET sensor for exosome detection with the capability for further improvements. The results were further supported by atomic force microscopy (AFM) and fluorescent microscopy measurements. The high-performance CDs-GFET biosensors will aid the development of an ultrahigh sensitivity biosensing platform based on graphene for rapid and early diagnosis of diseases.

This paper reports evidence for enhanced elemental interdiffusion during ultrasonic additive manufacturing (UAM) across metal boundaries of copper-aluminum, nickel-gold, and nickel-gold-aluminum. The high solute interdiffusion measured by energy dispersive X-ray spectroscopy line scans is rationalized with calculated vacancy concentrations orders of magnitude larger than thermal equilibrium values. The above estimates are supported by existing knowledge related to defect physics and UAM thermal cycles. The observation of pronounced elemental mixing are evidence for the presence of enhanced non-equilibrium immiscible metal interdiffusion during UAM processing.

A two-dimensional (2D) model was developed, for the first time, to describe the characteristics of the micromachined thermal expansion-based angular motion (TEAM) sensor, which has been validated by the experimental results. Scaling analysis on the performance characteristics through the 2D model was conducted to optimize the TEAM sensor’s design in terms of the normalized distances between the microheaters and temperature detectors in $x$ and $y$ directions, the thickness of the thin film, the heater width, the cavity depth, and the heater temperature. Furthermore, the proposed 2D model was normalized by two dimensionless numbers, namely Rayleigh number Ra and Peclet number Pe, with a critical Rayleigh number (Ra $^{\ast }_{\mathrm {c}} =18$ ,000) identified to differentiate linear and nonlinear operation regimes of the TEAM sensor. In particular, our 2D model is much faster than the conventional CFD model by three orders of magnitude (18.91s versus 5.5h), enabling rapid system-level optimization of the critical design parameters. Accordingly, the TEAM sensors with three pairs of platinum thermoresistive temperature sensors were designed and fabricated. The fabricated device demonstrated a normalized sensitivity of $11.8~\mu \text{V}$ /°/s/mW based on the working fluid of air, which was more than three times better than previous thermal angular motion sensors. Thus, with the experimental validation, the proposed 2D model should be a reliable tool to realize the systematical design optimization of TEAM sensors integrated with on-chip microelectronics for future industrial IoT applications. [2020-0355]

A new X-ray absorption spectroscopy (XAS) beamline is currently under construction at a bending magnet of the National Synchrotron Radiation Centre SOLARIS. The front end of this beamline was installed in April 2020. This beamline has a few outstanding characteristic features: The monochromator is a fixed exit beam Lemmonier type monochromator allowing to cover the pursued energy range (1 keV to ~15 keV) with 3 sets of crystals: KAP (100) + multilayer, InSb (111) and Ge (220). The monochromator is a high vacuum system allowing the change of crystals in less than an hour. In order to minimize absorption of photons no windows will be installed in the beamline down to the monochromator, and just one thin polypropylene window will be used for separating the vacuum of the monochromator from the ionization chambers and the sample chamber. A special differential ion pump will be installed to maintain the pressure difference of four orders of magnitude between the storage ring and the monochromator. As SOLARIS is a low energy machine, the beamline can be built without any radiation safety hutches without exceeding the strict low radiation safety levels. The straightforward design of the beamline without additional optical elements, its compact overall dimensions and an easy to handle monochromator make this beamline especially user friendly. In combination with the characteristics of the 1.5 GeV SOLARIS storage ring this beamline will be specifically attractive for the tender X-ray range, i.e. the K-edges of important elements such as P, S, Si, Al and Mg.

Developing point-of-care (PoC) diagnostic platforms for carcinoembryonic antigen detection is essential. However, thefew implementations of transferring the signal amplification strategies in electrochemical sensing on paper-based platforms are not satisfactory in terms of detection limit (LOD). In the quest for pushing down LOD, majority of the research has been targeted towards development of improved nanostructured substrates for entrapping more analyte molecules and augmenting the electron transfer rate to the working electrode. But, such approaches have reached saturation. This paper focuses on enhancing the mass transport of the analyte towards the sensor surface through the application of an electric field, in graphene-ZnO nanorods heterostructure. These hybrid nanostructures have been deposited on flexible polyethylene terephthalate substrates with screen printed electrodes for PoC application. The ZnO nanorods have been functionalized with aptamers and the working sensor has been integrated with smartphone interfaced indigenously developed low cost potentiostat. The performance of the system, requiring only 50 µl analyte has been evaluated using electrochemical impedance spectroscopy and validated against commercially available ELISA kit. Limit of detection of 1 fg/ml in human serum with 6.5% coefficient of variation has been demonstrated, which is more than three orders of magnitude lower than the existing attempts on PoC device.

This article reports humidity sensors based on hierarchical gallium nitride (GaN) with flower-like microstructures based on a scalable hybrid approach. We have fabricated 3D dandelion flower-like GaN hierarchical microspheres with an ammonothermal- conjugated ammoni- fication method (750-1150 °C) for the humidity sensors. The GaN microspheres are analyzed by scanning electron microscopy, X-ray diffraction, Raman and Fourier-transform spectroscopic methods. It is found that the use of oleylamine in the ammonothermal-ammonification hybrid approach, plays an essential role in the GaN morphology. The GaN sensors are prepared by dip-coating the sensor materials on the interdigitated electrode and their humidity sensing performance have been characterized. The humidity sensing performance is investigated at an applied 1V AC bias, by measuring the impedance and charge transfer resistance as a function of the broad range (10 to 95%) of RH. The GaN sensor exhibits a high response of above four orders of magnitude with excellent linearity and stability within the whole measurement range, while the bare GaN humidity sensors exhibited a low response of less than two orders of magnitude with poor linearity and stability. We have also proposed a possible charge transfer mechanism and studied the influence of the defect degree on the sensing performance of the GaN humidity sensors.

When a temperature gradient is applied to a closed circuit comprising two different conductors, a charge current is generated via the Seebeck effect1. Here, we utilize the Seebeck-effect-induced charge current to drive 'transverse' thermoelectric generation, which has great potential for energy harvesting and heat sensing applications owing to the orthogonal geometry of the heat-to-charge-current conversion2-9. We found that, in a closed circuit comprising thermoelectric and magnetic materials, artificial hybridization of the Seebeck effect into the anomalous Hall effect10 enables transverse thermoelectric generation with a similar symmetry to the anomalous Nernst effect11-27. Surprisingly, the Seebeck-effect-driven transverse thermopower can be several orders of magnitude larger than the anomalous-Nernst-effect-driven thermopower, which is clearly demonstrated by our experiments using Co2MnGa/Si hybrid materials. The unconventional approach could be a breakthrough in developing applications of transverse thermoelectric generation.

Deciphering the charge carrier dynamics in perovskite solar cells (PSCs) and electrical merits is essential to further improve the performance and operational stability. We investigated the charge carrier dynamics in triple cation-based PSCs through temperature dependent electrochemical impedance spectroscopy, thermal admittance spectroscopy, and space charge limited current (SCLC). The temperature dependent capacitance versus frequency (C–f) spectra reveal two kinds of activation process, one at low frequency and high temperature (>260 K), and the other at high frequency and low temperature (

Easy-to-use and sensitive quantification of biomarkers has a great significance in disease prediction, diagnosis, and monitoring. Here, we report a biosensor for simple and sensitive biomarker detection based on the strong light scattering (brightness) of superradiative plasmonic nanoantennas. This nanoantenna is constructed using antibody-decorated gold nanoparticles (Au NPs) immobilized onto a gold mirror by the target antigen, forming a nanoparticle-on-mirror (NPOM) configuration. The NPOM produces an order of magnitude stronger light scattering in the red region compared with isolated Au NPs on the dielectric substrate, due to the strong near-field coupling of surface plasmons across the gap between the Au NPs and the gold film. The increased brightness allows one to observe the captured Au NPs with the naked eye using a dark-field optical microscope. The particle density of the Au NPs varies linearly with the concentration of the target antigen over a broad dynamic range from 10-3 to 103 ng mL-1. This dynamic range is three orders of magnitude broader than that obtained from the previous work based on a dark-field optical microscope. The limit of detection is 1 pg mL-1 (6.67 fM), which is three orders of magnitude more sensitive than that obtained in the previous work using similar conditions. The uniform spatial distribution of the Au NPs on the gold film was allowed to quantify biomarkers with a relative standard deviation as small as 1-7%. Biosensing using superradiative NPs can lower the detection limit, simplify, and speed up the detection procedure for biomarker detection.

Objective. The article deals with the formation of cost-effective light transistors for creating high-speed energy-efficient computer structures that can solve numerous problems with high speed and accuracy. For this purpose, various types of semiconductor structures are used that can emit and absorb photons for receiving and transmitting digital information.Methods. The use of mirror electrodes allows for repeated re-reflection of the generated photons inside the light transistor to recover all the generated energy into electricity. This increases the energy efficiency of the transistor as a whole and allows implementing computer devices with high efficiency in solving various tasks.Results. Most of the useful energy of the information signal is transferred from one electrode to another, and the movement has a higher speed due to the use of photons, rather than drifting electrons, and this indirectly increases the speed of the light transistor by several orders of magnitude and effectively solves the problem of implementing more powerful and high-speed transistors with greater economic benefits.Conclusion. Prospects for the implementation of high-speed energy-efficient computer structures based on both bipolar transistors and unipolar transistors, as well as thyristors, lasers, and other semiconductor components in light-emitting structures have been developed.

This paper focuses on the development of a thin normal-shear force sensor based on the use of a supercapacitive sensing mechanism. The sensor has a quad structure with four sensing units in which the bottom substrate has four pairs of electrodes while the top deformable portion has a solid-state electrolyte. The application of normal and shear forces increases the contact area between the solid-state electrolyte and the electrodes. Key innovations in the sensing mechanism include the use of a paper-based solid state electrolyte, the use of 3d-printing with a combination of soft and hard polymers to construct the top portion of the sensor, and the use of deep learning to model the sensor response. The sensor can accept any combination of shear and normal forces and can measure both their magnitudes and orientation. The deep learning based sensor response model enables accurate sensor calibration while accommodating the imperfections in the stiffness distribution of the sensor. The normal and shear force sensitivities are of the order of 50 nF/N and 22 nF/N respectively, which are orders of magnitude larger than the sensitivity of a traditional capacitive force sensor.

A high-performance Bloch surface wave (BSW) sensor based on the hollow fiber (HF) inner coated with the one-dimensional photonic crystal (1DPC) consisting of TiO2 and SiO2 bilayers is proposed. Performances including sensitivity and figure of merit (FOM) of the sensor are investigated theoretically with the ray transmission model. Several structure parameters such as the center wavelength of 1DPC, the thickness of the cap layer and the bilayer period are optimized to obtain a best performance of the sensor. The results show that the proposed sensor has an ultra-high FOM over 1100 RIU-1, which is approximately two and one orders of magnitude higher than that of the HF surface plasmon resonance (SPR) sensor and HF long-range SPR sensor, respectively. Moreover, the proposed sensor has a much broader practical RI detection range, which makes it more useful in sensing applications. The performance of the proposed sensor applicated in temperature sensing is also estimated to prove its application potential.

Nonlinear diffraction of a plane electromagnetic wave from multilayer nonlinear metasurfaces consisting of double-period lattices of rectangular finite-length graphene ribbons on dielectric spacer layers is investigated in the terahertz (THz) frequency range. An increase in the third-harmonic generation efficiency by several orders of magnitude at the surface plasmon–polariton resonance frequencies is demonstrated. It is demonstrated that the third-harmonic frequency can be controlled by dynamic tuning of chemical potential without changing geometry or dimensions of the graphene metasurface.

The morphological control of nanomaterials plays a crucial role in enhancing the properties of nanomaterials. Regulating the dimension of nanomaterials through simple synthesis has always been the focus of scientists, especially for the dimensional regulation of rare earth oxides. In this paper, a simple controllable solvothermal self-assembly strategy was used to obtain Ho2O3 nanomaterials with three dimensions (1D, 2D, and 3D) and four different morphologies. The formation process, morphology regulation and structure of Ho2O3 nanomaterials were studied. The Ho2O3 nanomaterials were applied to humidity detection for the first time. The ultra-thin porous Ho2O3 NS humidity sensor shows the best response to humidity among the four samples. Its impedance has changed by nearly four orders of magnitude when the humidity changed from 11–95% RH. The response time and recovery time are only 0.3 s and 6 s, respectively. And the sensor also exhibits excellent repeatability and stability for humidity detection. More important is that new applications of the humidity sensor are developed to test human breathing vital signs, body surface humidity and the moisturizing effect of skin care products. This work provides a new method for developing high performance humidity sensors to monitor human vital signs and detect the efficacy of moisturizing products.

With the emergence of stretchable/wearable devices, functions, such as sensing, energy storage/harvesting, and electrical conduction, should ideally be carried out by a single material, while retaining its ability to withstand large elastic deformations, to create compact, functionally-integrated and autonomous systems. A new class of trimodal, stretchable yarn-based transducer formed by coating commercially available Lycra® yarns with PEDOT:PSS is presented. The material developed can sense strain (first mode), and temperature (second mode) and can power itself thermoelectrically (third mode), eliminating the need for an external power-supply. The yarns were extensively characterized and obtained an ultrahigh (gauge factor ∼3.6 × 105, at 10–20% strain) and tunable (up to about 2 orders of magnitude) strain sensitivity together with a very high strain-at-break point (up to ∼1000%). These PEDOT:PSS-Lycra yarns also exhibited stable thermoelectric behavior (Seebeck coefficient of 15 μV K−1), which was exploited both for temperature sensing and self-powering (∼0.5 μW, for a 10-couple module at ΔT ∼ 95 K). The produced material has potential to be interfaced with microcontroller-based systems to create internet-enabled, internet-of-things type devices in a variety of form factors.

The results of experimental and computational studies to identify the reasons for the increase in the vibration transmission through compensators of pipelines with liquid by several orders of magnitude with increasing frequency are considered. The descriptions of the found physical and computational models of this phenomenon are given. The results of experimental studies carried out on a special stand to study the possibility of reducing this transmission in a wide range of oscillation frequencies from 10 to 300 Hz by an order of magnitude or more by means of passive and active vibration damping methods are given. It has been shown experimentally that in the case of active spatial damping of dynamic forces behind the compensator, the mutual influence of the damping channels can significantly change the efficiency of the system.

Hybrid quantum optomechanical systems offer an interface between a single two-level system and a macroscopical mechanical degree of freedom. In this work, we build a hybrid system made of a vibrating microwire coupled to a single semiconductor quantum dot (QD) via material strain. It was shown a few years ago, that the QD excitonic transition energy can thus be modulated by the microwire motion. We demonstrate here the reverse effect, whereby the wire is set in motion by the resonant drive of a single QD exciton with a laser modulated at the mechanical frequency. The resulting driving force is found to be almost 3 orders of magnitude larger than radiation pressure. From a fundamental aspect, this state dependent force offers a convenient strategy to map the QD quantum state onto a mechanical degree of freedom., Comment: 16 pages, 12 figures

Experimental results of measuring the threshold power density of stimulated emission in coumarin-30 dye solutions with ZnO nanoparticles upon irradiation with femtosecond laser pulses are presented. It is shown that the stimulated emission thresholds of coumarin-30 dye solutions with incorporated ZnO nanoparticles upon irradiation with femtosecond laser pulses are approximately by 3 orders of magnitude higher than the stimulated emission thresholds of coumarin-30 dye solutions with incorporated ZnO nanoparticles irradiated with nanosecond laser pulses.

Nanocrystalline BiFeO3-based powder materials with an average crystallite size near 40 nm have been prepared by solution combustion synthesis from bismuth and iron nitrates using sucrose and tartaric acid as fuel. The materials have been characterized by X-ray diffraction, helium pycnometry, scanning electron microscopy, energy dispersive X-ray microanalysis, and Mossbauer spectroscopy. Magnetometry results demonstrate that the magnetic response of the materials varies over several orders of magnitude, depending on the synthesis procedure.

The development of high-performance glucose sensors is an urgent need, especially for diabetes mellitus diagnosis. However, the glucose monitoring is conventionally operated in an invasive finger-prick manner and their noninvasive alternatives largely suffered from the relatively poor sensitivity, selectivity, and stability, resulted from the lack of robust and efficient catalysts. In this paper, we design a concave shaped nitrogen-doped carbon framework embellished with single Co site catalyst (Co SSC) by selectively controlling the etching rate on different facet of carbon substrate, which is beneficial to the diffusion and contact of analyte. The Co SSC prompts a significant improvement in the sensitivity of the solution-gated graphene transistor (SGGT) devices, with three orders of magnitude better than those of SGGT devices without catalysts. Our findings expand the field of single site catalyst in the application of biosensors, diabetes diagnostics and personalized health-care monitoring.

The efficiency of the laser-induced desorption method as a detector of hydrogen isotopes under pulsed laser irradiation (wavelength 1064 nm, 100 mJ, duration 10 ns) for different power densities of incident radiation on deuterium-saturated thin titanium films was investigated. When the power flow density increases by 16 times, the intensity of the thermal desorption peak increases by more than 2 orders of magnitude. Long-term repeated irradiation of the surface does not lead to significant depletion of the content of hydrogen isotopes in the studied layers, allowing their further ex-situ analysis.

The canine olfactory system is a highly efficient and intricate tool often exploited by humans for detection for its many attributes, including impressive sensitivity to trace analyte vapors. Canine detectors are often touted as having lower limits of detection, or olfactory detection threshold (ODT), than other field-relevant detection technologies; however, previous attempts to quantify canine ODTs have resulted in reported estimates spanning multiple orders of magnitude, even for the same analyte. A major contributor to these discrepancies is the vapor delivery method used for testing, where losses due to adsorption and dilution are often unaccounted for, and the presence of unattended compounds in the vapor stream due to carryover may go unnoticed. In this research, a trace vapor generator (TV-Gen) was used to deliver quantitatively accurate amounts of vapor reproducibly over time for canine testing. Analyte losses due to adsorption to surfaces in the flow path, dilution in the sniff port at the outlet, and analyte carryover were considered. Computational fluid dynamic (CFD) modeling was used to visualize analyte vapor spread throughout the port. CFD simulations revealed the need for a diffuser to encourage the diffusion of the analyte throughout the port. As a result, the modified vapor generator provides analyte air as a diffuse flow that is evenly distributed through the custom sampling orifice, as opposed to a narrow stream of air at the chosen concentration which exits directly into the environment. Laboratory validations were carried out for three analytes, amyl acetate, 2,4-dinitrotoluene (DNT), and methyl benzoate. A linear response across more than two orders of magnitude vapor concentration range was achieved for all analytes. These efforts will be applied in further research utilizing this TV-Gen vapor delivery system for canine ODT testing, eliminating many quantitative changes seen previously. Graphical abstract.