Resolution Micro Research Articles

Gains from market integration: Welfare effects of new rural roads in Ethiopia

This paper estimates the welfare gains from the construction of rural roads that connect agricultural villages to market centers. I take theoretical predictions from Ricardian trade models to a rich high spatial resolution micro data on agricultural production from Ethiopia, which coincides with a period of extensive rural road construction. I estimate that the road construction resulted in an approximately 13% increase in real agricultural income, on average, and show that this increase is attributed to the mechanisms suggested in the Ricardian trade model: the prices of villages’ comparative advantage crops increased, and villages reallocated land for these crops following decreases in trade costs.

Abstract 662: A Novel Approach To Understanding Geometric Remodeling Of Surgically Created Arteriovenous Fistulas

Objectives: Failure of arteriovenous fistulas (AVF) for dialysis access remains a persistent problem. The reason for failure is largely unknown. Computational models of AVF have not been validated in parallel with animal experiments. We propose a computational AVF model that predicts venous geometric remodeling. We hypothesize that remodeling may precede AVF failure. Methods: First, we use a validated murine AVF model to define the parameters and boundary conditions for our computational model. Anesthetized mice undergo laparotomy and aortocaval puncture. Ultrasound confirms AVF patency, flow velocities, and vessel geometry throughout the aorta and inferior vena cava (IVC). In vivo CT angiography scans are segmented using 3D software (Simpleware ScanIP) to establish global geometry. We use this geometry to build a simplified geometric model which is then imported into a fluid dynamics simulation (Xflow) and finite element analysis software (Abaqus). Findings: Segmentations of in vivo CT scans establish the global geometry of the AVF (Fig 1a). A fluid dynamics model replicates flow through the fistula (Fig 1b). The model depicts the wall pressure being highest in the artery and around the fistula connection. A computational dynamics model predicts deformation and venous remodeling after pressurization of the system (Fig 1c). Conclusions: This is the first in vivo-computational model of AVF geometry. Our results indicate elevated wall pressure at the level of the fistula leads to venous deformation as hypothesized. These results can be used to predict how the underlying anastomotic geometry may impact anastomotic stress, stenosis, and injury, and may help define anatomic parameters that could optimize AVF durability. Future experiments involving models using the in vivo geometry itself, higher resolution micro CT images, and histologic staining of the vessel wall will provide insight into the deformation mechanisms around these observed areas of remodeling.

An effective system for evaluating the performance of micro pore optics used for lobster eye X-ray telescope

Fabricating and evaluating the high angular resolution micro pore optics (MPO) used for the Lobster eye X-ray telescope has been challenging and essential since its advent. We developed two sets of X-ray test equipment suitable for industrial batch production, which evaluate the optical quality of flat and spherical chips. At the voltage was 2 kV, the current was 0.1 mA, and the best angular resolution of the flat and spherical chip was 2.7 arcmins and 3.4 arcmins, respectively. The simulation results show that the tilt and distort channel errors mainly affected the shape of the point spread function, similar to the X-ray measurement results.

Experimental Analysis of Wax Micro-Droplet 3D Printing Based on a High-Voltage Electric Field-Driven Jet Deposition Technology

High-voltage electric field-driven jet deposition technology is a novel high resolution micro scale 3D printing method. In this paper, a novel micro 3D printing method is proposed to fabricate wax micro-structures. The mechanism of the Taylor cone generation and droplet eject deposition was analyzed, and a high-voltage electric field-driven jet printing experimental system was developed based on the principle of forming. The effects of process parameters, such as pulse voltages, gas pressures, pulse width, pulse frequency, and movement velocity, on wax printing were investigated. The experimental results show that the increasing of pulse width and duration of pulse high voltage increased at the same pulse frequency, resulting in the micro-droplet diameter being increased. The deposited droplet underwent a process of spreading, shrinking, and solidifying. The local remelting and bonding were acquired between the contact surfaces of the adjacent deposited droplets. According to the experiment results, a horizontal line and a vertical micro-column were fabricated by adjusting the process parameters; their size deviation was controlled within 2%. This research shows that it is feasible to fabricate the micro-scale wax structure using high-voltage electric field-driven jet deposition technology.

Molecular Imaging of Pulmonary Tuberculosis in an Ex-Vivo Mouse Model Using Spectral Photon-Counting Computed Tomography and Micro-CT

Assessment of disease burden and drug efficacy is achieved preclinically using high resolution micro computed tomography (CT). However, micro-CT is not applicable to clinical human imaging due to operating at high dose. In addition, the technology differences between micro-CT and standard clinical CT prevent direct translation of preclinical applications. The current proof-of-concept study presents spectral photon-counting CT as a clinically translatable, molecular imaging tool by assessing contrast uptake in an ex-vivo mouse model of pulmonary tuberculosis (TB). Iodine, a common contrast used in clinical CT imaging, was introduced into a murine model of TB. The excised mouse lungs were imaged using a standard micro-CT subsystem (SuperArgus) and the contrast enhanced TB lesions quantified. The same lungs were imaged using a spectral photoncounting CT system (MARS small-bore scanner). Iodine and soft tissues (water and lipid) were materially separated, and iodine uptake quantified. The volume of the TB infection quantified by spectral CT and micro-CT was found to be 2.96 mm3 and 2.83 mm3, respectively. This proof-of-concept study showed that spectral photon-counting CT could be used as a predictive preclinical imaging tool for the purpose of facilitating drug discovery and development. Also, as this imaging modality is available for human trials, all applications are translatable to human imaging. In conclusion, spectral photon-counting CT could accelerate a deeper understanding of infectious lung diseases using targeted pharmaceuticals and intrinsic markers, and ultimately improve the efficacy of therapies by measuring drug delivery and response to treatment in animal models and later in humans.

High Efficient GaN Based Micro LEDs for High Re-solution Micro LED Displays

High Efficient GaN Based Micro LEDs for High Re-solution Micro LED Displays

A soft and stretchable bilayer electrode array with independent functional layers for the next generation of brain machine interfaces

Objective. Brain-Machine Interfaces (BMIs) hold great promises for advancing neuroprosthetics, robotics, and for providing treatment options for severe neurological diseases. The objective of this work is the development and in vivo evaluation of electrodes for BMIs that meet the needs to record brain activity at sub-millimeter resolution over a large area of the cortex while being soft and electromechanically robust (i.e. stretchable). Approach. Current electrodes require a trade-off between high spatiotemporal resolution and cortical coverage area. To address the needs for simultaneous high resolution and large cortical coverage, the prototype electrode array developed in this study employs a novel bilayer routing of soft and stretchable lead wires from the recording sites on the surface of the brain (electrocorticography, ECoG) to the data acquisition system. Main results. To validate the recording characteristics, the array was implanted in healthy felines for up to 5 months. Neural signals recorded from both layers of the device showed elevated mid-frequency structures typical of local field potential (LFP) signals that were stable in amplitude over implant duration, and also exhibited consistent frequency-dependent modulation after anesthesia induction by Telazol. Significance. The successful development of a soft and stretchable large-area, high resolution micro ECoG electrode array (lahrμECoG) is an important step to meet the neurotechnological needs of advanced BMI applications.

The study on electric field distribution and droplet trajectory during electrohydrodynamic jet printing

EHD (Electrohydrodynamic) printing is a photomask-free and direct writing technique for alternative fabrication of high resolution micro- and nano-structures with low cost and simple equipment. It is critical to understand the motion trajectory of the ejected droplet under electric filed so as to precisely control the printing process. However, there is no work which analyzed this issue previously. Thus in this paper, a finite element model was established to study the electric field distribution near the nozzle and analyze the motion trajectory of the ejected droplet during EHD printing. By using established finite element method, the electric field distribution in the nozzle and near the nozzle tip was investigated. The influence of printing distance and applied potential on the maximum electric field intensity was analyzed. Based on the electric field distribution study, the droplet trajectory analysis was carried out to confirm the motion velocity and direction of the ejected droplets.

37‐4: Micro LED Defect Analysis via Photoluminescent and Cathodoluminescent Imaging

Ultra‐high resolution micro LED displays are emerging as a viable technology for self‐emissive displays. One challenge for displays with millions of pixels is process control and defect analysis during LED fabrication and transfer. Here we investigate two non‐destructive test methods, photoluminescent and cathodoluminescent imaging, and compare them to electroluminescent images to verify LED fidelity and evaluate these methods as potential tools for defect analysis.

The fabrication of integrated and three-layer SU-8 nozzles for electrohydrodynamic printing

Electrohydrodynamic (EHD) jet printing can fabricate high resolution micro- and nano-scale lines with low cost and simple procedure. However, less attention has been paid to the fabrication of integrated nozzles with low cost and volume production capacity. In this work, three-layer SU-8 nozzles with slot dimension ranging from 10 to 50 μm were fabricated by ultraviolet photolithography and thermal bonding methods. The influence of the thicknesses (bottom and top layers) on the deformation of SU-8 nozzle was studied by numerical simulation. The results show that the suitable thicknesses should be 60 and 10 μm for bottom and top layer, to ensure the fabrication quality of SU-8 nozzles. Based on the established EHD printing platform, PEO (Polyethylene Oxide) lines with line-width from 750 nm to 8.2 μm can be printed by using the fabricated SU-8 nozzles, indicating the indicating the practicality of developed nozzle fabrication method.

Combined Hind Limb Suspension and sRANK-L on Bone Strength in Mice by Finite Element Analysis: Effects of Anatomic Model Height.

With commercial space travel on the horizon, it is important to understand how the microgravity environment of space effects bone strength. The reduction in skeletal loading is known to cause a rapid loss in bone density. How this corresponds to losses of bone strength is not well known, especially when combined with the osteoporotic effects of aging. In this study, a mouse model of hind limb suspension (HLS) was used to simulate the effects of gravitational unloading. This was combined with soluble receptor activator of nuclear factor kappa beta ligand (sRANK-L), which simulates age related osteoporosis. The proximal region of the tibia in mouse legs was scanned in-vivo pre-treatment as well as at the conclusion of the study with high resolution micro computed tomography (µCT). Subject specific finite element (FE) models were constructed from these 3D images to assess bone strength by simulating mechanical loading on these bone microstructures. Parameters indicative of bone strength obtained from the FE models were bone volume, stiffness, structural efficiency, and the 10th and 90th percentile nodal Von-Mises Stresses. Additionally, a model sensitivity analysis was performed to assess how these parameters varied with changes in anatomic model height. In regards to FE stiffness, HLS resulted in a 31% decline, sRANK-L resulted in a 16.8% decline, and HLS combined with sRANK-L (HLS+sRANK-L) resulted in a 38.6% decline. One interesting finding is that HLS caused a reduction in both bone stiffness and bone structural efficiency, while sRANK-L did not cause changes in bone structural efficiency, suggesting the importance of skeletal loading for maintaining bone health. In addition, sRANK-L combined with HLS caused an additional decline in bone stiffness, but did not further alter bone structural efficiency. In conclusion, this study shows that depending on the cause of osteoporosis, bone strength changes are not necessarily proportional to bone density changes. Thus, it is important to develop new clinical bone assessments beyond the current bone density measurement.Clinical Relevance- These parameters are associated with the microstructural mechanics of bone, and understanding how strength is decreased on a structural level may lead to the development of in-vivo bone strength testing clinically.

A Corner Detection Method for Conventional Light Field Camera by Jointly Using Line-Features

Micro-lens array (MLA) based light field cameras have been commercialized and had a wide range of applications in various fields in recent years. To promote these applications, especially for 3D reconstruction, it is crucial to calibrate light field cameras. Among the calibration steps, it is of great importance to detect corners in checkerboard images and establish the point-to-point correspondence between the checkerboard and its images. However, almost all existing algorithms detect corners in the sub-aperture images instead of raw images for conventional light field cameras. In this paper, a corner detection algorithm that can recognize corners in the raw images of conventional light field cameras was proposed. Firstly, template matching was used to detect the 3D lines in the image space of the main lens. Then, the locations of the corners were obtained by calculating the intersection of 3D line segments and reprojecting it to the raw image again. Experimental results have demonstrated that the algorithm can still achieve good performance in actual datasets with blurred and low resolution micro lens image.

An economic and concise method to solve nozzle clogging issue during electro hydrodynamic printing

Electro hydrodynamic (EHD) printing is a promising technique for alternative fabrication of high resolution micro- and nano-structures without employment of any molds or photo-masks. However, a major problem, nozzle clogging, often occurs when the viscosity of the inks or the size of ink particles is raised. We proposed in this work an economic and concise method to solve the nozzle clogging issue. A PDMS-glass disassembled nozzle was designed and fabricated, which can be bonded under pressure and separated after pressure release. The influence of substrate material, bonding pressure, aspect ratio and channel-size on the dimension loss of PDMS micro-channel was investigated by an established simulation method. It is expected that the proposed method has great potential for fabrication of reusable nozzle without the clogging problem.

Ultrashort echo time magnetic resonance imaging (UTE-MRI) of cortical bone correlates well with histomorphometric assessment of bone microstructure.

Ultrashort echo time magnetic resonance imaging (UTE-MRI) techniques have been increasingly used to assess cortical bone microstructure. High resolution micro computed tomography (μCT) is routinely employed for validating the MRI-based assessments. However, water protons in cortical bone may reside in micropores smaller than the detectable size ranges by μCT. The goal of this study was to evaluate the upper limit of UTE-MRI and compare its efficacy to μCT at determining bone porosity ex vivo. This study investigated the correlations between UTE-MRI based quantifications and histomorphometric measures of bone porosity that cover all pores larger than 1 μm. Anterior tibial midshaft specimens from eleven donors (51 ± 16 years old, 6 males, 5 females) were scanned on a clinical 3 T-MRI using UTE magnetization transfer (UTE-MT, three power levels and five frequency offsets) and UTE-T2* sequences. Two-pool MT modeling and bi-component exponential T2* fitting were performed on the MRI datasets. Specimens were then scanned by μCT at 9 μm voxel size. Histomorphometry was performed on hematoxylin and eosin (H&E) stained slides imaged at submicron resolution. Macromolecular fraction from MT modeling, bi-component T2* fractions, and short component T2* showed strong correlations (R > 0.7, p < 0.01) with histomorphometric total and large-pores (>40 μm) porosities as well as with μCT-based porosity. UTE-MRI could also assess small pores variations with moderate correlations (R > 0.5, p < 0.01). The UTE-MRI techniques can detect variations of bone porosity comprised of pores below the range detectable by μCT. Such fine pore variations can contribute differently to the development of bone diseases or to the bone remodeling process, however, this needs to be investigated. In scanned specimens, major porosity changes were from large pores, therefore the μCT employment was likely adequate to validate UTE-MRI biomarkers.

Elastic properties of sands, Part 2: Implementation of contact‐based model to determine the elasticity of the grains from ultrasonic measurements

ABSTRACTThe prediction of effective elastic properties of a granular medium using ultrasonic data based on contact models has been studied widely in both laboratory experiments and numerical simulations. In contrast, a calculation of the elastic properties of the constituent grains using similar data by inverting the equations from those models is a rather new concept. To do so, we have developed a controlled experiment technique that includes a uniaxial compaction test and measures ultrasonic velocities of four unconsolidated quartz sand samples with different sorting and grain shapes. We observe that both P‐ and S‐wave velocities are significantly influenced by the microstructure or internal arrangement of the grains. Well sorted and more spherical and rounded samples show higher velocities than the poorly sorted and less spherical and rounded samples. A microstructural parameter – namely coordination number – we have calculated from high resolution micro computed tomography images provides a good match between the model and dynamic effective bulk moduli of the sand pack. Combining this coordination number with a frictional parameter calculated from the measured velocity ratios has been very effective to fit the model with the dynamic effective shear moduli. Using these two key parameters along with the experiment results in the contact model we have been able to obtain the elastic parameters of the quartz sand grains in the sample. Elastic parameters obtained thus are very close to the actual values of the quartz grains found in the literature. This technique can be useful in hard rock mineral exploration where missing core samples or an absence of well logs can be replaced by laboratory measurements of powders to find the elasticity or velocities of the rocks. Moreover, the elastic properties of the solid phase calculated using this technique can be used as input parameters for the fluid substitution and rock physics characterization of unconsolidated reservoir sands.

59‐2: Invited Paper: Ultra‐Fine Pitch Thin‐Film Micro LED Display for Indoor Applications

In this paper, we will review the development of micro‐LED in ITRI, and demonstrate the latest results of the full‐color, and high resolution micro display with fine pitch of micro‐LED arrays. The devices can be mass‐transferred onto different substrates, such as printed circuit boards or glass plates. The micro‐LED performance is measured and its reliability under temperature cycle and high current condition show great stability in both forward voltage and output power.

Evaluation of width and width uniformity of near-field electrospinning printed micro and sub-micrometer lines based on optical image processing

This paper presents an experimental study using image processing to investigate width and width uniformity of sub-micrometer polyethylene oxide (PEO) lines fabricated by near-filed electrospinning (NFES) technique. An adaptive thresholding method was developed to determine the optimal gray values to accurately extract profiles of printed lines from original optical images. And it was proved with good feasibility. The mechanism of the proposed thresholding method was believed to take advantage of statistic property and get rid of halo induced errors. Triangular method and relative standard deviation (RSD) were introduced to calculate line width and width uniformity, respectively. Based on these image processing methods, the effects of process parameters including substrate speed (v), applied voltage (U), nozzle-to-collector distance (H), and syringe pump flow rate (Q) on width and width uniformity of printed lines were discussed. The research results are helpful to promote the NFES technique for fabricating high resolution micro and sub-micro lines and also helpful to optical image processing at sub-micro level.

A Backprojection Slice Theorem for Tomographic Reconstruction.

Fast image reconstruction techniques are becoming important with the increasing number of scientific cases in high resolution micro and nano tomography. The processing of the large scale 3D data demands new mathematical tools for the tomographic reconstruction. Due to the high computational complexity of most current algorithms, big data sizes demands powerful hardware and more sophisticated numerical techniques. Several reconstruction algorithms are dependent on a mathematical tool called backprojection (a transposition process). A conventional implementation of the backprojection operator has cubic computational complexity. In the present manuscript we propose a new fast backprojection operator for the processing of tomographic data, providing a low-cost algorithm for this task. We compare our formula against other fast transposition techniques, using real and simulated large data sets.

Evaluation of scratch resistance of nitride coatings on Ti grade 2

Hard coatings limiting direct contact of material susceptible to wear are applied in order to improve resistance to abrasive wear. The key importance in using anti-wear coatings has their adhesion to substrate and differences in mechanical properties of the coating and substrate, particularly their Young's module. Studies have analyzed merits of applying nitride coatings TiAlN, AlTiN and hybrid coating TiAlN/TiSiN on titanium substrate ASTM grade 2. For that purpose, nanohardness and scratch tests for each coating were conducted. Apparatus of Anton Paar Company was used in these studies – ultra-high resolution nanoindenter and micro combi tester. Due to the fact, that surface roughness is a significant parameter affecting properties of the surface layer, the first appointed parameters were Sa roughness with a use of optical profilometer Bruker Contour GT. Obtained results suggest the best adhesive grip of hybrid coating TiAlN/TiSiN compared with other tested. The weakest adhesion to titanium grade 2 has TiAlN coating, on which in scratch test has been observed significantly faster total damage, in comparison with other tested. Research results will provide the input data for numerical analysis, enabling fast receiving effects of applying tested coatings without the need to carry out time-consuming research.

Experimental and simulation study of carbon dioxide, brine, and muscovite surface interactions

Capture and subsequent geologic storage of CO2 in deep brine reservoirs plays a significant role in plans to reduce atmospheric carbon emission and resulting global climate change. Subsurface injection of CO2 is also used industrially in enhanced oil and natural gas recovery operations to increase the amount of hydrocarbon that can be economically recovered from a geologic reservoir. The interaction of CO2 and brine species with mineral surfaces controls the ultimate fate of injected CO2 at the nanoscale via surface chemistry, at the pore-scale via capillary trapping, and at the field-scale via relative permeability. High resolution micro X-ray CT scanning, optical contact angle measurements, and large scale molecular dynamics simulations were used to investigate the behavior of supercritical CO2 and aqueous fluids on basal surfaces of muscovite, a common phyllosilicate mineral. Experimental results demonstrate partial wetting by the aqueous phase and a dependence of contact angle upon aqueous phase brine composition. This contrasts with simulation results, which predict that supercritical CO2 forms a non-wetting droplet, separated from direct interaction with the muscovite surface by distinct layers of water and charged species. Simulations with trace amounts of acetate or acetic acid added to the CO2/water/mineral system were used to investigate the potential effect of contamination with small organic molecules. While the observed contact angle was not significantly altered, these simulations demonstrate the influence of pH on species partitioning, with acetic acid molecules partitioning to the CO2/water interface and acetate ions adsorbing to the mineral surface. Similar simulations using hexanoate displayed a greater surfactant effect and significantly increased wetting by the CO2 phase, suggesting that small concentrations of secondary species or contaminants can significantly influence macroscopic wetting behavior.