In-plane Position Research Articles

Controlled lateral positioning of NV centres in diamond by CVD overgrowth

A challenge to this day in the development of diamond devices for quantum applications is the laterally defined and closely spaced positioning of nitrogen-vacancy centres with exceptional coherence properties. Here, we demonstrate a maskless, implantation-free method for the controlled in-plane positioning of NV centres using a combination of focused ion beam (FIB) milling, plasma etching and nitrogen-doped diamond growth. The Ga+ ion beam milling resulted in 1 μm × 1 μm cavities with depths of up to 450 nm, each cavity exhibiting the four [111]-oriented diamond facets after pure hydrogen plasma treatment and a depth of 700 nm. Low-methane, nitrogen-doped chemical vapour deposition (CVD) overgrowth resulted in in situ formation of oriented NV ensembles, exclusively perpendicular to the {111}-planes.

Identifying and fixing in-plane positioning and stability issues on a microscope using machine-readable patterned position scales

Investigations of the in-plane positioning capabilities of microscopes using machine-readable encoded patterned scales are presented. The scales have patterns that contain absolute position information, and adequate software accurately determines the in-plane position from the scale images captured by the microscope camera. This makes in-plane positioning experiments simple and fast. The scales and software used in this study are commercially available. We investigated different microscopy systems and found that positioning performance is a system issue that is not determined solely by stage performance. In some cases, our experiments revealed software or hardware glitches that limited the positioning performance, which we easily fixed. We have also shown that it is possible to investigate vibrations using this approach and quantify their impact on image blurring. This is, for example, useful for experimentally determining the settling time after a stage movement.

Spatial Position Regulation of Cu Single Atom Site Realizes Efficient Nanozyme Photocatalytic Bactericidal Activity.

Recently, single-atom nanozymes have made significant progress in the fields of sterilization and treatment, but their catalytic performance as substitutes for natural enzymes and drugs is far from satisfactory. Here, a method is reported to improve enzyme activity by adjusting the spatial position of a single-atom site on the nanoplatforms. Two types of Cu single-atom site nanozymes are synthesized in the interlayer (CuL /PHI) and in-plane (CuP /PHI) of poly (heptazine imide) (PHI) through different synthesis pathways. Experimental and theoretical analysis indicates that the interlayer position of PHI can effectively adjust the coordination number, coordination bond length, and electronic structure of Cu single atoms compared to the in-plane position, thereby promoting photoinduced electron migration and O2 activation, enabling effective generate reactive oxygen species (ROS). Under visible light irradiation, the photocatalytic bactericidal activity of CuL /PHI against aureus is ≈100%, achieving the same antibacterial effect as antibiotics, after 10min of low-dose light exposure and 2h of incubation.

Effect of porosity and pore size distribution on elastic modulus of foams

In this study, we investigate the impact of pore distribution and size on the mechanical response of elastic porous materials. Two-dimensional porous media with convex porosity are considered (e.g., foams and sponges). These structures are numerically generated by subtracting randomly dispersed circular holes from a solid square domain. The in-plane position vector of pore centers is given by a uniform probability density function (PDF). The pore diameters are, instead, drawn from a non-uniform two-parameter continuous probability distribution. The influence of the void ratio, i.e., the volume fraction of voids, and the parameters of the diameter PDF are studied over a wide range of values, including the percolation threshold, where the effective elastic modulus of the material abruptly drops to zero. This transition takes place at a critical value of the void ratio, which turns out to be unaffected by the parameters of the pore size distribution. Our results demonstrate that the elastic response of these structures is primarily governed by the void ratio, with the correlation length playing a secondary role. While the pore size distribution may affect the correlation length, it has a minimal impact on the foam’s overall behavior.

A deep neural network architecture for reliable 3D position and size determination for Lagrangian particle tracking using a single camera

Microfluidic flows feature typically fully three-dimensional velocity fields. However, often the optical access for measurements is limited. Astigmatism or defocus particle tracking velocimetry is a technique that enables the 3D position determination of individual particles by the analysis of astigmatic/defocused particle images. The classification and position determination of particles is a task well suited to deep neural networks (DNNs). In this work, two DNNs are used to extract the class and in-plane position (object detection) as well as the depth position (regression). The performance of both DNNs is assessed by the position uncertainties as well as the precision of the size classes and the amount of recalled particles. The DNNs are evaluated on a synthetic dataset and establish a new benchmark of DNNs in defocus tracking applications. The recall is higher than compared to classic methods and the in-plane errors are always subpixel accurate. The relative uncertainty in the depth position is below 1% for all examined particle seeding concentrations. Additionally, the performance on experimental images, using four different particle sizes, ranging from 1.14 to 5.03 is analyzed. The particle images are systematically rearranged to produce comprehensive datasets of varying particle seeding concentrations. The distinction between particles of similar size is more challenging but the DNNs still show very good results. A precision above 96% is reached with a high recall above 95%. The error in the depth position remains below 1% and the in-plane errors are subpixel accurate with respect to the labels. The work shows that first, DNNs can be trained with artificially rearranged data sets based on individual experimental images and are therefore easily adaptable to various experimental setups and applicable by non-experts. Second, the DNNs can be successfully adapted to determine additional variables as in this case the size of the suspended particles.

Investigation of aluminum current collector degradation in lithium-ion batteries using glow discharge optical emission spectrometry

In this work, we employed glow discharge optical emission spectrometry (GD-OES) depth profiling as a fast and semi-quantitative method to investigate the aluminum (Al) current collector degradation in commercial lithium cobalt oxide (LCO) pouch cells with no Al2O3 pretreatment. After battery aging, a heterogeneous deposit was found on the surface of the cathode. Gray hotspot areas within an extensive pale white region were formed. Consistent with energy dispersive X-ray (EDX) analysis of micro-cross sections milled via targeted focused ion beam (FIB), an Al-containing layer of approximately 3 μm can be observed using GD-OES. We attribute one main cause of this layer is the degradation of the Al current collector. The nonuniform growth of this layer was investigated by performing GD-OES depth profiling at different in-plane positions. We found that the gray area has a higher mass concentration of Al, probably in metallic form, whereas the white area was probably covered more homogeneously with Al2O3, resulting from the inhomogeneous distribution of the pitting positions on the current collector. Compared to FIB-EDX, GD-OES enables a faster and more convenient depth profile analysis, which allows the more productive characterization of lithium-ion batteries (LIBs), and consequently benefits the development of preferable battery materials.

In-Mould OCT Sensors Combined with Piezo-Actuated Positioning Devices for Compensating for Displacement in Injection Overmoulding of Optoelectronic Parts

When overmoulding optoelectronic devices with optical elements, precise alignment of the overmoulded part and the mould is of great importance. However, mould-integrated positioning sensors and actuators are not yet available as standard components. As a solution, we present a mould-integrated optical coherence tomography (OCT) device that is combined with a piezo-driven mechatronic actuator, which is capable of performing the necessary displacement correction. Because of the complex geometric structure optoelectronic devices may have, a 3D imaging method was preferable, so OCT was chosen. It is shown that the overall concept leads to sufficient alignment accuracy and, apart from compensating for the in-plane position error, provides valuable additional information about the sample both before and after the injection process. The increased alignment accuracy leads to better energy efficiency, improved overall performance and less scrap parts, and thus even a zero-waste production process might be feasible.

In-plane charged domain walls with memristive behaviour in a ferroelectric film.

Domain-wall nanoelectronics is considered to be a new paradigm for non-volatile memory and logic technologies in which domain walls, rather than domains, serve as an active element. Especially interesting are charged domain walls in ferroelectric structures, which have subnanometre thicknesses and exhibit non-trivial electronic and transport properties that are useful for various nanoelectronics applications1-3. The ability to deterministically create and manipulate charged domain walls is essential to realize their functional properties in electronic devices. Here we report a strategy for the controllable creation and manipulation of in-plane charged domain walls in BiFeO3 ferroelectric films a few nanometres thick. By using an in situ biasing technique within a scanning transmission electron microscope, an unconventional layer-by-layer switching mechanism is detected in which ferroelectric domain growth occurs in the direction parallel to an applied electric field. Based on atomically resolved electron energy-loss spectroscopy, in situ charge mapping by in-line electron holography and theoretical calculations, we show that oxygen vacancies accumulating at the charged domain walls are responsible for the domain-wall stability and motion. Voltage control of the in-plane domain-wall position within a BiFeO3 film gives rise to multiple non-volatile resistance states, thus demonstrating the key functional property of being a memristor a few unit cells thick. These results promote a better understanding of ferroelectric switching behaviour and provide a new strategy for creating unit-cell-scale devices.

Zooming-Free Hand-Eye Self-Calibration for Nanorobotic Manipulation Inside SEM

Nanorobotic manipulation inside Scanning Electron Microscope (SEM) is widely used in nanomaterial characterization and assembly tasks. However, tedious and time-consuming hardware regulations, like axis alignment, are still critical and mandatory to keep the functionality of nanorobot systems. This paper proposes a novel zooming-free hand-eye self-calibration method for nanorobotic manipulation inside SEM to circumvent the hardware regulation problem, which is applicable to a wide range of system configurations. The hand-eye relationship calibration method is based on the active incremental motion of the nanorobot without referring to expensive and complicated calibration patterns. Both perspective projection at low magnification and affine projection at high magnification are modelled, and unified by the image Jacobian matrix technique. With several times active calibration at different magnification factors in advance, the hand-eye relationship can be, thereafter, determined from the model at arbitrary status. The calibration model can be applied to both accurate SEM visual measurement and precision visual servo control. The corresponding methods regarding two-dimensional (2D) measurement, in-plane positioning, and constrained three-dimension (3D) positioning based on the proposed hand-eye relationship model are also presented in this paper. Experiments show that practical contact between robot end-effector and silicon nanowire under 1500× is well established with standard deviation less than one pixel.

Absolute Quantification of Pure Free Radical Reagents by Combination of the Effective Magnetic Moment Method and Quantitative Electron Paramagnetic Resonance Method.

An absolute quantitative analysis of free radicals by combining the effective magnetic moment method and the quantitative electron paramagnetic resonance [qEPR] method is proposed. This combined method utilizes the advantages of both the analytical methods and compensates for their disadvantages. In the effective magnetic moment method, the magnetic moment under a constant magnetic field is measured accurately using a superconducting quantum interference device. The qEPR method compares a "primary standard sample" and "secondary standard sample". The effective magnetic moment method was used to determine the purity of the primary standard sample. The qEPR method realizes a simple purity analysis of free-radical reagents with traceability to the International System of Units (SI). The purity of the free radicals by the qEPR method for pure 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl benzoate [4HTB], 1-oxyl-2,2,6,6-tetramethyl-4-hydroxypiperidine [TEMPOL], and di(phenyl)-(2,4,6-trinitrophenyl)iminoazanium [DPPH] reagents was obtained with a relative expanded uncertainty of 0.7% for 4HTB to 1.5% for the DPPH. These small uncertainties were almost equal to those of the purity of the primary standard samples and were achieved by adopting in-plane positioning of the measured sample perpendicular to the cylindrical axis of the sample space of the superconducting quantum interference device. Some purity values of the free radicals for these reagents differed from those stated by the manufacturers. This combined method enables short-time quality control of pure radical reagents, instead of quality control by separation analytical methods or titrations.

Supplemental Peak Filters for Advanced Disturbance Rejection on a High Precision Endeffector for Robot-Based Inline Metrology

This article presents a metrology platform (MP) as high precision endeffector of a robot with a tailored disturbance rejection scheme in order to enable high-resolution measurements directly in a production line. The MP is installed on a gantry robot for in-plane positioning and has an electromagnetic actuator for vertically positioning its mover. It can mount a compact measurement tool for high precision topography measurements, which are typically sensitive to external vibrations, introducing relative motion between the measurement tool and the sample. To compensate these vibrations, the MP mover vertically tracks the sample by feedback control, maintaining a constant distance between sample and measurement tool. In order to reject broad-band floor vibrations as well as narrow-band vibrations, revealed by the analysis and introduced by the robots servo control, the designed high-bandwidth proportional-integral differential based controller is supplemented by peak filters tailored to the narrow-band vibration components. A method for designing these peak filters depending on the location of the narrow-band disturbance relative to the crossover frequency is presented. The resulting controller enables a tracking error as small as 15 nm (rms), which is 50% smaller than the error without the peak filters, demonstrating the effectiveness of the MP in enabling high-resolution inline measurements.

Three-dimensional failure behaviour of L-shaped laminated composite with wrinkles and defects

In this paper, three-dimension failure behaviour of L-shaped composite beam with manufacturing defects was studied under four-point bending test condition. First, X-ray computed tomography scan was performed for L-shape laminated composite beam specimen to detect manufacturing defects such as voids, pre-delamination, and wrinkles or ply waviness. The scan images were then converted to three-dimensional volumetric entity through image processing, from which finite element mesh was generated with the detected defects directly incorporated. Next, three-dimensional progressive failure analysis was performed for the finite element model of the L-shaped laminate composite simulating four-point bending test condition with delamination and matrix failure in 90 degree plies accounted for by using cohesive zone modelling. The predicted maximum load was well matched to that obtained by tests validating the analysis modeling. Then a series of parametric studies were performed to investigate the effect of defect size and location on the failure load and delamination propagation pattern. It was found that the maximum load reduction was the largest when the pre-defect was located at the center of the symmetrical portion of the L-beam. In addition, the maximum load and delamination development behavior varied significantly depending on the interlayer and in-plane position of the pre-defect.

Out-of-Plane Vibration Suppression and Position Control of a Planar Cable-Driven Robot

Cable-driven parallel robots (CDPRs) are more convenient to use in large-scale applications than rigid-link robots due to the advantages such as simple structure, high load capacity, and low inertia of cables. However, using cables to drive an end-effector comes with the low equivalent stiffness issue in out-of-plane direction for the CDPRs’ planar configuration, which causes long-lasting and high amplitude out-of-plane vibrations under an external disturbance. This article presents a novel method to suppress the out-of-plane vibrations without distorting in-plane positioning control simultaneously for planar CDPRs. The proposed method provides the ease of using only the cable tensioning forces instead of an additional actuator to control the out-of-plane vibrations by decoupling the in-plane and out-of-plane dynamics. The switching stiffness control method is used for out-of-plane vibration control, while a classical control method is used for in-plane dynamics control. These two control inputs are then coupled by a bias torque variation in a torque distribution algorithm. The effectiveness of the proposed method is presented both in simulations and experimental results. The experiments are performed for the specified in-plane positions and an in-plane trajectory tracking study when the planar CDPR is excited to out-of-plane vibration in the normal direction. The out-of-plane vibration suppression time is considerably reduced compared to the free-vibration case, and any distortion on the in-plane positioning control is not observed.

An electrostatically suspended contactless platform

Electrostatic suspension of a silicon disk with explicit control of the lateral translational degrees-of-freedom is reported. The transduction subsystem configures electrode pairs to exert electrostatic forces on the disk and to also measure differential capacitances related to the disk position. Disk sidewall forcing electrodes are not necessary to control the disk’s lateral position because tilting the disk relative to the plane of the electrodes exerts lateral forces on the disk. Despite the fact that the disk’s lateral and angular degrees-of-freedom are strongly coupled, the system is not strongly stabilizable using only the disk’s vertical position and tilt estimates derived from electrode–disk gap measurements. Nevertheless, a stabilizing controller is proposed and lateral position measurements are added for regulating the disk’s in-plane position. Extensive experimental results corroborate the model and analysis.

Imaging vibrations of electromechanical few layer graphene resonators with a moving vacuum enclosure

Imaging the vibrations of nanomechanical resonators means measuring their flexural mode shapes from the dependence of their frequency response on in-plane position. Applied to two-dimensional resonators, this technique provides a wealth of information on the mechanical properties of atomically-thin membranes. We present a simple and robust system to image the vibrations of few layer graphene (FLG) resonators at room temperature and in vacuum with an in-plane displacement precision of ≈0.20 μm. It consists of a sturdy vacuum enclosure mounted on a three-axis micropositioning stage and designed for free space optical measurements of vibrations. The system is equipped with ultraflexible radio frequency transmission lines to electrically actuate resonators. With it we characterize the lowest frequency mode of FLG resonators by measuring its frequency response as a function of position on the membrane and by extracting its effective mass. We use the background noise of the undriven vibrational spectrum to calibrate in-plane displacement. Finally, we measure the first three vibration modes of a resonator whose membrane is partially folded and find that folds locally suppress vibrations.

Reliability-based Design Optimization of Laminated Composite Structures under Delamination and Material Property Uncertainties

Delamination is a major type of defects from manufacturing process in laminated composite structures, exhibiting uncertain characteristics which are represented by mixed random variables of continuous in-plane position and delamination size, as well as discrete through-the-thickness position, which should be considered in the design phase of composite structures. Thus, this paper presents a reliability-based design framework for optimal design of composite stacking sequence, for the first time to consider both delamination and material property uncertainties from manufacturing process. Mixed continuous-discrete random variables are involved, and a reliability analysis method is newly proposed to tackle this mixed-variable problem, maintaining high levels of both accuracy and efficiency. The formula of total probability is first employed to formulate the reliability constraint so that discrete and continuous random variables are decoupled; Monte Carlo simulation is then used for reliability analysis with respect to continuous random variables, and a surrogate modelling approach based on Gaussian process regression model is adopted to reduce computation costs. As design variables of ply angles are limited to a discrete set, a genetic algorithm with some proposed improvements is used to handle discrete design variables. Consequently, an optimization framework is devised for composite laminate design under uncertainties from manufacturing process, which is verified via case studies of a cantilever composite plate and can also be extended as a general solution for other composite laminates. With integrated consideration of manufacturing limitations and imperfections as well as structural performances, the presented framework provides a valuable tool in composite structure design.

Synthesis, Material and Electrical Characterization Combined with DFT Calculations of Reduced SnO2-x

Introduction: The use of Density Functional Theory (DFT) simulations to predict the chemical-physical properties of nanostructured compounds and heterogeneous interactions (solid-gas) has become almost essential today, both to predict the properties of technologically advanced nanomaterials and to overcome the limits of experimental characterizations.Specifically, the use of DFT calculations can likewise be used in chemoresistive gas sensor applications, to investigate the physical-chemical properties of nanostructured semiconductors and their possible catalytic activity. Among the various gas sensing materials used, the Metal Oxide Semiconductors (MOXS) are the most investigated since the excellent sensitivity, good stability and low cost of production [1,2]. Nevertheless, besides all of these advantages they present also some drawbacks such as signal drift over the time, lack of selectivity and high operating temperature.Investigators have tried to address these problems in several manners, including the synthesis of solid solutions composed of different metal oxides, doping these materials with deferent kinds of elements and also with controlled concentrations of oxygen vacancies. The latter is a field still little explored, but preliminary experimental and theoretical works highlighted interesting results [3,4].When the sensor is exposed to a reducing (oxidizing) gas, the gas molecules interact with the chemisorbed oxygen species from the surrounding atmosphere and then decrease (increase) the resistance of a n-type based gas sensor, and vice versa for a p-type semiconductor. This change in resistance is due to the exchange of electrons between the surface and the conduction band. For a stoichiometric semiconductor, the electrons involved in this reaction that are in the conduction band are coming from the valence band after heating the material, in this case they need a high energy to blow up from the valence band to the conduction band. But when one introduces some defects, new energy level will be created and then they will be a new electrons source, thus the energy that the sensor needs to be thermoactivated decrease; that is energy that electrons need to jump to the conduction band. Scope and Methods: The purpose of this work is to investigate the impact of oxygen vacancies inside MOXS on their physical-chemical properties in general and on the electrons exchange in particular. Indeed, the creation of oxygen vacancies influences the physical-chemical properties of metal oxides. i.e. The bridging oxygen vacancies lead to the formation of energy level in the band gap region (Fig.1), these energy levels will behave as electrons donors that decrease the energy (ε1) needed for the electrons to be in the conduction band. While creation of oxygen vacancies from in-plane positions drives to the formation of impurity levels located slightly below the conduction band minimum (CBM), in this case the energy (ε2) that they need to jump to the conduction band is lower than ε1. Therefore, we can say that in-plane oxygen vacancies can overcome the disadvantage of high working temperatures for MOXS; as much as the electrons resource is close to the conduction band, as much as the ionization of these electron levels will be easy and then enhance the reactions (adsorption process) on the surface of the active element at low temperature.Tin dioxide is a typical n-type semiconducting material with a wide band gap of 3.6 eV. It has attracted the attention of many researchers because of its broad spectrum of physicochemical properties. It has also been used in several fields such as optoelectronic devices, electrocatalysis, ceramics and gas sensors. It is the semiconductor most studied as active element for the production of chemoresistive gas sensors. Then, it represents the best candidate for the proposed innovative work.In this work, DFT was used to compute the physical-chemical properties of the considered material. The Local Density Approximation (LDA) and the Generalized Gradient Approximation (GGA), which improve the LDA results taking into account the electron density gradient due to the non-homogeneity of the electron density, are the principal basis of the exchange-correlation functional within the framework of DFT. In this work, the GGA parameterized PBE (Perdew-Burke-Ernzerhof) has been used for structural properties prediction. This approximation has demonstrated, beside the LDA, their ability to predict the structural properties of materials. Nevertheless, their applications underestimate the band gap energy of materials compared to experimental results. To enhance the results concerning the band gap the Tran-Blaha’s modified Becke-Johnson exchange potential model (TB-mBJ) has been applied, this approximation has proved its ability to predict the band gap of materials.A series of first-principles studies has been carried out using the Full Potential Linearized Augmented Plane Wave (FPLAPW) method within the framework of the DFT, as implemented in the Wien2k code. This method is the most effective method to solve the Khon Sham equation.

Analytic solution of in-plane vortex\u2013rotor interactions with arbitrary orientation and its impact on rotor trim

The general aerodynamic problem of arbitrarily oriented in-plane vortex-rotor interaction was investigated in the past only by numerical simulation. Just one special case of in-plane vortex-rotor interaction with the vortex axis in flight direction was recently solved analytically. In this article, the analytical solution for arbitrary in-plane vortex orientation and position relative to the rotor is given for the first time. The solution of the integrals involved as derived here encompasses and simplifies the previous derivation of the special case significantly. Results provide the vortex impact on rotor trim (thrust, aerodynamic rolling and pitching moments about the hub) and the rotor controls required to mitigate these disturbances. For the special case with the vortex axis in flight direction, the results are identical to the former solution and results for the other in-plane vortex orientations and positions agree with the numerical results obtained so far.

Deep velocimetry: Extracting full velocity distributions from projected images of flowing media

Particle image velocimetry (PIV) is a powerful image correlation method for measuring bulk velocity fields of flowing media. It typically uses optical images, representing quasi-two-dimensional experimental slices, to measure a single velocity value at each in-plane position. However, projection-based imaging methods, such as x-ray radiography or shadowgraph imaging, encode additional out-of-plane information that regular PIV is unable to capture. Here, we introduce a new image analysis method, named deep velocimetry, that goes beyond established PIV methods and is capable of extracting full velocity distributions from projected images. The method involves solving a deconvolution inverse problem to recover the distribution at each in-plane position, and is validated using artificial data as well as controlled laboratory x-ray experiments. The additional velocity information delivered by deep velocimetry could provide new insight into a range of fluid and granular flows where out-of-plane variation is significant.Graphic abstract

Robust Phase-Based Decoding for Absolute (X, Y, Θ) Positioning by Vision

Computer vision is a convenient noncontact tool for position control and thus constitutes an attractive multidirectional alternative to widely used single-direction sensors. However, to meet actual industry requirements, vision-based measurement methods must be sufficiently robust to comply with industrial environments. This article explores the robustness of an in-plane position measurement method based on a pseudoperiodic pattern and allowing a 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sup> range-to-resolution ratio in displacement and a 1-μ rad angular resolution over 2π rad. This article shows how the pattern phase can be used to maintain reliable measurements despite defocus, discrepancies in local contrast, nonuniform illuminations, or occlusions. The proposed method can be implemented at different size scales with unique capabilities combining high resolution, large measurement range, and robustness to diverse kinds of disturbances.