Imprint Area Research Articles

Návrh programu pre automatické vyhodnotenie obrazu výtlačku zosnímaného CCD kamerou

The aim is to create a program for the automatic evaluation of hardness from a series of images taken by a CCD camera. We will present the different functions of the proposed program. In the first step, we created an algorithm that selects the image with the most suitable sharpness from a series of images of different sharpness. In the second step, we created an algorithm that evaluated the imprint area on the selected image, from which it computed the resulting hardness. We then incorporate the algorithms into a single resulting program. We compare he measurements of the program with measurements at the University of Žilina and on a manual V 10/HT instrument.

Software Support for Evaluating the Hardness Tests of Construction Materials Used in Vehicles

The goal is to create a program for the automatic evaluation of hardness using a series of images taken by a charge-coupled camera (CCD). It will be explained the importance of materials testing for applications in vehicle design. We will present a specially developed program in Matlab to graphically display the surface hardness field of the object under study. The focus of the research is the evaluation of the hardness according to Vickers. In the first step, we developed an algorithm to select the image with the most appropriate sharpness from a series of images of different sharpness. In the second step, we created an algorithm that evaluated the imprint area in the selected image, from which the resulting hardness was calculated. Then we integrated the algorithms into a single resulting program. We compare the measurements of the program with measurements on an automatic ST-2000 Zwick Roell instrument and a manual V 10/HT instrument.

Identification technology based on geometric features of tooth print images

Identity recognition technology is a type of technology that realizes identity verification based on certain biological characteristics. After entering the Internet era, this technology has become a popular research direction in the computer field. In this paper, the image of the tooth print is used as the biological feature to carry out the research on the identification algorithm. This paper adopts the target detection algorithm based on neural network to detect a single tooth imprint area of the target, build a target detection network. The experimental results show that the method has a good segmentation effect on the target area, and the accuracy rate is 91.66%. According to the contour features of the collected tooth print images, a set of tooth pore area ratio feature extraction methods are designed. To objectively evaluate the recognition and classification method, the support vector machine is used as the final classifier. The recognition accuracy rate is 94.09%, and the verification accuracy rate is 94.09%. The test accuracy rate is 91.46%, and the classification effect is excellent. This paper has made a lot of breakthroughs and obvious progress based on the previous research on the tooth impression model.

Establishment of mechanisms for the occurrence of blood imprints, taking into account their qualitative and quantitative indicators

The purpose of the study is to establish the mechanisms for the formation of blood imprints, taking into account morphological features and some quantitative indicators of these blood traces. An analysis of the results of experimental modeling of contact marks (blood prints) resulting from the impact of a gloved hand is presented. The type of impact (shock, pressure) and duration of pressure (short-term pressure 1 - 3 sec, long-term pressure 20 - 120 sec) were determined. Under impact, the main elements of prints are formed regardless of the absorbent properties of trace-forming and trace-receiving objects: a) their contours (edges) are uneven, finely and coarsely serrated; b) the central part of the trace with an uneven thickness of the blood layer; c) second splashes are oval, spindle-shaped, ray-shaped (needle-shaped) and in the form of an exclamation mark; d) medium-speed elements - dynamic blood flows encircling or strip-like (long and narrow, short and wide). The absorbent properties of the trace-receiving material under pressure do not have a significant effect on the formation of the main elements of the traces: a) the contours (edges) of the prints are relatively even; b) the central part of the trace is more pronounced than the peripheral part, which is more clearly visualized on non-absorbent materials; c) low-velocity elements - «dynamic streaks» of blood are strip-like (short and narrow), appear only with sharp pressure, regardless of the exposure of the contact. For traces-imprints from long-term pressure, in contrast to short-term pressure, the following is characteristic: a) the thickness of the trace is on average 1.3-1.6 times greater with a high degree of significant difference in indicators (p<0.001); b) more uniform distribution of blood over the imprint area with a high degree of significant difference in indicators (from p<0.002 to p<0.001); c) clearer and smoother contours with a high degree of significant difference in indicators (p<0.002).

Effect of Shear Stresses on Asphalt Pavement Performance and Evaluating Debonding Potential under Repeated Loading: Numerical Study

The primary of this paper is to evaluate the potential of shear failure in asphalt pavement with the primary focus on the layer interface debonding. To fulfill this objective, a three-dimensional (3D) finite-element (FE) model is developed to calculate the stress state within the asphalt pavement structure. Five different cases of vehicle maneuvering where shear forces acting on the surface layer were selected, and pavement responses were obtained and analyzed under 100 loading cycles at three different temperatures. Results show that maximum shear stress occurred on top of the surface layer, and with receding from the surface, the stresses reduced significantly along the pavement depth. The case where the vehicle moves along the curved road section induced the highest transverse shear stress, whereas braking action caused the highest longitudinal shear stress both within the pavement layer and at the layer interface. Moreover, the maximum shear stress in both directions and all studied cases took place in somewhere within the tire imprint area. With increasing temperature, the pavement responses increased in all cases accordingly. In addition, pavement responses at the bottom of the binder course were significantly lower than those of at the bottom of the surface layer. In general, pavement responses in pavement layers were larger than their counterparts at the layer interface. Finally, the concept of interface shear ratio (ISR) is presented to evaluate the potential of debonding at the layer interface under repeated loading. According to initial results, the ISR could be considered as a promising criterion for assessing shear failure potential at layer interface.

Investigation of micromechanical properties of fused alumina and silicone carbide grains

Micromechanical properties of abrasive material grains of fused alumina and silicone carbide are investigated applying the microindentation method. Such parameters as microhardness, microbrittleness, and microstrength were evaluated depending on the penetration depth of the Vickers diamond pyramid to the 0.5 — 5.0 µm thick surface under analysis. The microhardness parameter is the stress required for formation of a brittle failure area within the pyramid imprint. The microbrittleness criterion defines the ratio of the brittle failure area within the imprint and the imprint area. The power-law dependence of the parameters on the pyramid penetration depth is established: the lower the depth, the higher are microhardness and microstrength, yet the lower is microbrittleness. The obtained results enable creation of a standard basis, forecasting of the performance level of abrasive tools, refractory and wear-resistant items, filters, and special ceramics.

Research on feature extraction and segmentation of rover wheel imprint

The wheel imprint photograph of the rover contains important information such as wheel motion parameters, soil characteristic parameters and movement status of the rover. Segmenting the wheel imprint area from the photograph is an important prerequisite for feature extraction and parameter identification. Traditional image segmentation cannot take both speed and precision into account because they are based on a wide range of image object attributes, such as grayscale threshold, color, texture, gradient, contrast, shape and size. This paper presents an image segmentation method based on the wheel imprint feature. Compared to other common graphics segmentation methods, the morphological characteristics and frequency domain characteristics of the wheel imprint are found out by analyzing the mechanism of the wheel–terrain interaction process, and the eigenvector is also constructed. In the wheel trace feature space, the clustering algorithm is used to divide the image into the trace area and the non-trace area. The segmentation accuracy and processing speed were used to evaluate the algorithm. The experimental results show that the developed algorithm based on the characteristics of wheel imprint formation mechanism is more accurate and efficient than the traditional method.

Neural-like computing with populations of superparamagnetic basis functions

In neuroscience, population coding theory demonstrates that neural assemblies can achieve fault-tolerant information processing. Mapped to nanoelectronics, this strategy could allow for reliable computing with scaled-down, noisy, imperfect devices. Doing so requires that the population components form a set of basis functions in terms of their response functions to inputs, offering a physical substrate for computing. Such a population can be implemented with CMOS technology, but the corresponding circuits have high area or energy requirements. Here, we show that nanoscale magnetic tunnel junctions can instead be assembled to meet these requirements. We demonstrate experimentally that a population of nine junctions can implement a basis set of functions, providing the data to achieve, for example, the generation of cursive letters. We design hybrid magnetic-CMOS systems based on interlinked populations of junctions and show that they can learn to realize non-linear variability-resilient transformations with a low imprint area and low power.

Alternate approach for calculating hardness based on residual indentation depth: Comparison with experiments

It is well known that plastic deformation is a highly nonlinear dissipative irreversible phenomenon of considerable complexity. As a consequence, little progress has been made in modeling some well-known size-dependent properties of plastic deformation, for instance, calculating hardness as a function of indentation depth independently. Here, we devise a method of calculating hardness by calculating the residual indentation depth and then calculate the hardness as the ratio of the load to the residual imprint area. Recognizing the fact that dislocations are the basic defects controlling the plastic component of the indentation depth, we set up a system of coupled nonlinear time evolution equations for the mobile, forest, and geometrically necessary dislocation densities. Within our approach, we consider the geometrically necessary dislocations to be immobile since they contribute to additional hardness. The model includes dislocation multiplication, storage, and recovery mechanisms. The growth of the geometrically necessary dislocation density is controlled by the number of loops that can be activated under the contact area and the mean strain gradient. The equations are then coupled to the load rate equation. Our approach has the ability to adopt experimental parameters such as the indentation rates, the geometrical parameters defining the Berkovich indenter, including the nominal tip radius. The residual indentation depth is obtained by integrating the Orowan expression for the plastic strain rate, which is then used to calculate the hardness. Consistent with the experimental observations, the increasing hardness with decreasing indentation depth in our model arises from limited dislocation sources at small indentation depths and therefore avoids divergence in the limit of small depths reported in the Nix-Gao model. We demonstrate that for a range of parameter values that physically represent different materials, the model predicts the three characteristic features of hardness, namely, increase in the hardness with decreasing indentation depth, and the linear relation between the square of the hardness and the inverse of the indentation depth, for all but 150 nm, deviating for smaller depths. In addition, we also show that it is straightforward to obtain optimized parameter values that give good fit to the hardness data for polycrystalline cold worked copper and single crystals of silver.

A Theoretical Study of Indentation with an Oblate Spheroid Shape

In this study, firstly we introduced general mathematical concepts related to the geometrical form of ellipse and ellipsoid. Secondly, the hardness was calculated when we used an indenter having a geometrical shape of an oblate spheroid; the mathematical expressions of static hardness were determined as functions of the applied load, the radius or the depth of the imprint area. The general static hardness formula was expressed considering the projected and the real area imprint of the oblate spheroid indenter. Thirdly mathematical assumptions were introduced in order to simplify the mirohardness and nanohardness formulas when we used the real imprint area. Finally we did a comparative study between the oblate spheroid and the spherical indenters.

Direct observation of contact on non transparent viscoelastic polymers surfaces: A new way to study creep and recovery

Abstract This work presents a new instrumentation dedicated to the study of contact creep and recovery of non transparent polymeric samples. The aim is to be able to analyze viscoelastic properties of polymeric surfaces recording the apparent contact area for the contact creep phase and the residual imprint area for the recovery phase. This gives valuable information not to be model dependant in the analysis compared to classical techniques. Indeed, for the creep phase many methods have been proposed to estimate the contact area, but rarely perform direct vizualisation as we propose. For the recovery phase two main challenges arise: avoid contact probe not to influence on recovery kinetics; get recording at early times to have information before recovery is quite finished. This study focus on indentation problems to prove the concept of viscoelastic analysis directly from experimental data without modeling. But the problematic is more larger than that and widen to more complicated rheological surface studies including indentation and scratching.

In-situ Observation of Cross-Sectional Microstructural Changes and Stress Distributions in Fracturing TiN Thin Film during Nanoindentation.

Load-displacement curves measured during indentation experiments on thin films depend on non-homogeneous intrinsic film microstructure and residual stress gradients as well as on their changes during indenter penetration into the material. To date, microstructural changes and local stress concentrations resulting in plastic deformation and fracture were quantified exclusively using numerical models which suffer from poor knowledge of size dependent material properties and the unknown intrinsic gradients. Here, we report the first in-situ characterization of microstructural changes and multi-axial stress distributions in a wedge-indented 9 μm thick nanocrystalline TiN film volume performed using synchrotron cross-sectional X-ray nanodiffraction. During the indentation, needle-like TiN crystallites are tilted up to 15 degrees away from the indenter axis in the imprint area and strongly anisotropic diffraction peak broadening indicates strain variation within the X-ray nanoprobe caused by gradients of giant compressive stresses. The morphology of the multiaxial stress distributions with local concentrations up to −16.5 GPa correlate well with the observed fracture modes. The crack growth is influenced decisively by the film microstructure, especially by the micro- and nano-scopic interfaces. This novel experimental approach offers the capability to interpret indentation response and indenter imprint morphology of small graded nanostructured features.

Air density of the Permian atmosphere: Constraints from lithified raindrop imprints

In contrast to the composition of Earth's ancient atmosphere, the corresponding air density is almost unknown. A unique method to estimate the palaeo-atmospheric density is to use lithified raindrop imprints. The size of imprints is amongst other factors controlled by the air density, whereas large impacts form in a less dense atmosphere and vice versa. This basic relation was used to estimate the near sea-level atmospheric density of the Permian, a period characterised by an icehouse to greenhouse transition and an atmospheric composition comparable to the modern one. This makes the Permian an important analogue to better understand the current climate and environmental changes. In this study we analysed lithified raindrop imprints preserved in Permian terrestrial sandstone from the Flechting High, northern Germany. Following former applications, we experimentally determined the relation between raindrop momentum and imprint dimension to estimate the palaeo-air density. The maximum bound of the Permian air density is ~2.3kg/m3, assuming that the maximum measured imprint area of 68±1.5mm2 was formed by the largest naturally occurring raindrop with a diameter of 6.8mm. Although we cannot rule out an air density comparable to the present day (~1.2kg/m3), more realistic estimates of maximum raindrop diameters for a rainfall rate of 100mm/h are between >3.2 and >4.3mm, yielding air density estimates of 0.3 and 0.85kg/m3, approximately one-fourth to three-quarters of the present-day value. This approach is based on a few largest observed imprints, and does take the complete raindrop imprint distribution into account. The imprint distribution primarily depends on the drop size distribution of the rainfall event that causes the imprints, which follow a defined function. In this study we present a novel method to further constrain the palaeo-air density estimation by comparing the observed distribution of lithified raindrop imprints with modelled imprint distributions for different rainfall rates and drop size distribution functions. We observed significant differences; theoretical imprint distributions are in general shifted towards smaller imprints, which we interpret as a higher probability of larger imprints to be preserved. Above a threshold imprint area of 10mm2, observed and modelled distributions match each other, suggesting that a major fraction (~50%) of raindrops did not generate recognisable imprints in the analysed substrate. Unfortunately no unique rainfall rate fits the observed imprint distribution, but instead pairs of rainfall rates and air densities yield reasonable fits. Palaeo-air density estimates therefore depend on an unknown rainfall rate. Assuming that lithified imprints formed by a rain event with a rainfall rate of <100mm/h (<50mm/h) result in an upper estimate of the Permian atmospheric air density of ~1.1kg/m3 (~0.9kg/m3). These results corroborate estimates based on the maximum observed imprint area and realistic maximum raindrop diameters, suggesting that the Permian atmospheric air density was comparable or slightly lower than the present-day density.

Application of Dry Nano Powder Inverse Imprint Technology in Transferring and Replication of Micro Patterns

Abstract This research aims to develop a new dry nano powder inverse imprint technology, and probe into transferring and replication of micro patterns. First, a polydimethylsiloxane (PDMS) mould surface, with micro patterns of grating structures, undergo activation treatment with oxygen plasma in order to improve mould surface energy, and thus, spin coat photoresist onto the surface more easily. Then, the surface is heated to restore its hydrophobicity, and by means of nano powder, micro patterns are transfer printed onto the polymethylmethacrylate (PMMA). Research results show that dry nano powder soft coat transferring and forming technology can accurately reproduce the required patterns. In the experiment, gas assisted nano powder imprint technology is used to apply even pressure, coupled with even temperature rise for solidification, then, patterns can be effectively transfer printed and completely formed. Further, these patterns are in perfect contact with the PMMA surface, thus, greatly increasing the valid imprint area and enhancing transferring reproductiveness. The technology integrates technologies, such as, soft lithography, solidifying photoresist, and gas assisted pressure application, and is utilized to transfer print micro patterns in a grating structure, and thus, complete the transferring process of dry micro structure patterns.

Experimental and Numerical Study of Spread and Sorption of VX Sessile Droplets into Medium Grain-Size Sand

The experimental measurement and modeling of liquid chemical agent spread and sorption on a porous substrate are described. Experimental results with the nerve agent O-ethyl S-(2-diisopropylaminoethyl) methylphosphonothiolate (VX) demonstrate that the wetted imprint volume increases, even after the sessile drop volume is exhausted. This indicates the wetted imprint is only partially saturated, and a multiphase flow problem formulation is needed to predict the VX fate in porous substrates. Three characteristics and their changes in time: (i) sessile volume remaining, (ii) wetted imprint area on the sand surface where the droplet is deposited, and (iii) VX penetration depth into sand, are computed numerically and compared to experimentally measured values. A very good qualitative and quantitative agreement was found between the numerical and experimental results. These numerical and experimental methods can be used to determine the spread and sorption of hazardous materials into a variety of substrates.

An assessment of the process capabilities of nanoimprint lithography

Nanoimprint lithography (NIL) is an emerging nanofabrication tool, able to replicate imprint patterns quickly and at high volumes. The present study was performed in order to define the capabilities of NIL, based on a study of published research and to identify the application areas where NIL has the greatest potential. The process attributes of different NIL process chains were analysed, and their process capabilities were compared to identify trends and process limitations. The attributes chosen include the line width, relief height, initial resist thickness, residual layer thickness, imprint area and line width tolerances. In each case well-defined limits can be identified, which are a direct result of the mechanisms involved in the NIL process. These quantitative results were compared with the assessments of individuals in academia and within the microfabrication industry. The results suggest NIL is most suited to producing photonic, microfluidic and patterned media applications, with photonic applications the closest to market. NIL needs to address overlay alignment issues for wider use, while an analysis is needed for each market, as to whether NIL adds value.

Control of Parameters Influencing the Thermal Imprint of Parylene/Silicon

The study aims to investigate the possible defects that may occur during imprinting of poly(chloro- p-xylylene) (parylene-C) film (thermal oxidation, delamination, thermal cracking and insufficient filling at the periphery) and to overcome them by modifying the process conditions and mold design. X-ray diffraction (XRD) analyses results for the parylene-C films indicated that higher deposition pressure leads to a lower crystallinity of parylene-C film. By tuning the process conditions and mold design, patterned fields (composed of arrays of 25-µm-high, 10-µm-wide and 1-mm-long lines with 10 µm spacing) in 0.4-mm-thick and 20-mm-sized nickel molds could be successfully replicated on 60-µm-thick parylene-C films deposited at both 25 and 45 mTorr. Complete filling over the whole imprint area could be achieved at <270 °C with the press force at 2 kN and the press hold time of 900 s with the aid of an implemented dummy pattern. Both thermal cracking and delamination could be avoided, even at 270 °C, under the established process conditions and mold design with the help of an adhesion promotion treatment of silicon substrates (SF6 plasma etching for 2 min and spin-coating of KBM-503-based solution). Furthermore, the molds used for paryelne imprinting could be cleaned by dipping in chloronaphthalene solution at >175 °C, followed by an oxygen plasma etching.

Control of Bubble Defects in UV Nanoimprint

We studied UV nanoimprint in air and the elimination of bubble defects using pentafluoropropane, which has a vapor pressure of 0.15 MPa at 25 °C. Bubble defects are unavoidable when UV nanoimprint is carried out in air. Pillars fabricated in thin resin film by UV nanoimprint in air contain bubble defects since bubbles are not eliminated by resin squeezing and only a small amount of air is dissolved in the resin. By introducing pentafluoropropane under such experimental condition, bubble elimination by gas condensation was separately investigated. The bubble elimination phenomenon is completed within a few seconds under an imprint pressure of 0.5 MPa in a sufficiently high concentration of pentafluoropropane. No bubble defects are generated in the entire imprint area of 10×10 mm2 with an imprint pressure of 0.5 MPa at a hold time longer then 20 s and a pentafluoropropane flow higher than 150 sccm.

Elastomeric imprint lithography process based on distortion reduction by precure press releasing

Due to the conflict between the imprint area and the parallelity of mould and wafer,the elastometric imprint lithography is described.The loading process and the key technology of this process are analyzed and the error factors during pattern transferring process are also mined.Through comparing among the loading process factors,the conflict be- tween the pattern transferring accuracy and residual resist thickness is indicated.By adjusting the elastic restore step be- fore the UV-cure step,a novel imprint process-DRPPR,distor- tion reduction by precure press releasing is established and the inner conflict can be eliminated,and the imprint area can be lifted from 2 cm~2 to 8 cm~2.Based on the novel imprint lithog- raphy process,a low cost and simple structure prototype ma- chine of step imprint lithography is designed and fabricated, and a series of imprint experiments show that the new imprint process can meet the needs for different pressing areas,feature sizes and repetitious imprints.

Photo-Nanoimprinting Using Sample-on-Flexible-Thruster Stage

We designed a novel sample stage named sample-on-flexible-thruster (SOFT) stage, which has a unique compliant contact mechanism working on the sample side, and installed it in a full-function photo-nanoimprinter. The pressing uniformity of an imprint area using the SOFT stage was preserved with a tolerance of 1 mrad in parallelism between a mold and a wafer. Such parallelism requires no adjustment once the mold is preset to an appropriate orientation. Pressing uniformity is improved using a soft pad, which supports a wafer backside, of the SOFT stage. The built-in flexible thruster of the SOFT stage controls wafer warping precisely with a force resolution of 0.01 N and a full contact between the mold and sample accompanied by air evacuation in a warping contact sequence. The thickness uniformity of cured resin using the SOFT stage was 9.8 nm for an initial resin thickness of 160 nm. The SOFT stage enables step-and-repeat photo-nanoimprinting for an initial resin thickness of as small as 60 nm. The SOFT stage separates the compliant contact mechanism from the mold side and realizes flexible arrangements of mark detection and UV illumination on the mold side of the full-function photo-nanoimprinter.