Micron Level Research Articles

Quantification of cavitating flows with neutron imaging

The current experimental investigation demonstrates the capability of neutron imaging to quantify cavitation, in terms of vapour content, within an orifice of an abruptly constricting geometry. The morphology of different cavitation regimes setting in was properly visualised owing to the high spatial resolution of 16 μm achieved, given the extensive field of view of 12.9 × 12.9 mm2 offered by the imaging set-up. At a second step, the method was proven capable of highlighting subtle differences between fluids of different rheological properties. More specifically, a reference liquid was comparatively assessed against a counterpart additised with a Quaternary Ammonium Salt (QAS) agent, thus obtaining a viscoelastic behaviour. In accordance with previous studies, it was verified, yet in a quantifiable manner, that the presence of viscoelastic additives affects the overall cavitation topology by promoting the formation of more localised vortical cavities rather than cloud-like structures occupying a larger portion of the orifice core. To the authors’ best knowledge, the present work is the first to demonstrate that neutron imaging is suitable for quantifying in-nozzle cavitating flow at the micrometre level, consequently elucidating the distinct forms of vaporous structures that arise. The potential of incorporating neutron irradiation for the quantification of two-phase flows in metallic microfluidics devices has been established.

Effect of Air Pollutants and Environmental Noise on the Childhood Asthma Prevalence in Tehran, Iran

The purpose of this study is to investigate the effect of air pollutants and noise on the prevalence of childhood asthma in Tehran, Iran. The standardized questionnaire was completed by one of the parents of children aged 6–7 years or by adolescents aged 13–14 years. The asthma prevalence in ages 6-7 and 13–14 was found to be 8.8% and 17.44%, respectively. A significant positive association was observed between “ever wheezing” and monoxide carbon (CO) concentration (OR=1.84, 1.05-3.25 in 13–14 years), the occurrence of 4 to 12 wheezing attacks and sulfur dioxide (SO2) concentration (Odds Ratio [OR]=1.39, 1.04-1.91) and particulate matter less than 2.5 micron (PM2.5) concentration (OR=1.38, 1.05-1.98 and OR=1.13, 0.98-1.39 in 6-7 and 13–14 years, respectively), as well as one night per week of sleep disturbances and nitrogen dioxide (NO2) concentration (OR=1.09, 1.03-1.16 in 6–7 years, respectively). It was also found that there was a significant interaction between the noise level and particulate matter less than 10 microns (PM10) level. Based on the findings, exposure to certain outdoor air pollutants and noise can affect the prevalence of asthma symptoms in residents of Tehran. The simultaneous presence of air pollutants and noise has an aggravating effect on the prevalence of asthma symptoms. Therefore, controlling sources of pollutants for reducing asthma symptoms is suggested.

Controlled Fabrication of Wafer-Scale, Flexible Ag-TiO2 Nanoparticle-Film Hybrid Surface-Enhanced Raman Scattering Substrates for Sub-Micrometer Plastics Detection.

As an important trace molecular detection technique, surface-enhanced Raman scattering (SERS) has been extensively investigated, while the realization of simple, low-cost, and controllable fabrication of wafer-scale, flexible SERS-active substrates remains challenging. Here, we report a facile, low-cost strategy for fabricating wafer-scale SERS substrates based on Ag-TiO2 nanoparticle-film hybrids by combining dip-coating and UV light array photo-deposition. The results show that a centimeter-scale Ag nanoparticle (AgNP) film (~20 cm × 20 cm) could be uniformly photo-deposited on both non-flexible and flexible TiO2 substrates, with a relative standard deviation in particle size of only 5.63%. The large-scale AgNP/TiO2 hybrids working as SERS substrates show high sensitivity and good uniformity at both the micron and wafer levels, as evidenced by scanning electron microscopy and Raman measurements. In situ bending and tensile experiments demonstrate that the as-prepared flexible AgNP/TiO2 SERS substrate is mechanically robust, exhibiting stable SERS activity even in a large bending state as well as after more than 200 tensile cycles. Moreover, the flexible AgNP/TiO2 SERS substrates show excellent performance in detecting sub-micrometer-sized plastics (≤1 μm) and low-concentration organic pollutants on complex surfaces. Overall, this study provides a simple path toward wafer-scale, flexible SERS substrate fabrication, which is a big step for practical applications of the SERS technique.

A qualitative validation of an in-situ monitoring system for EHD inkjet printing via laser diffraction

Electrohydrodynamic inkjet printing enables high-resolution patterning for nano features. In-flight dynamics of EHD inkjet printing play an essential role in the quality control of printing results. We applied a laser diffraction/scattering in-situ analyzing setup for the EHD inkjet printing system to replace the zoom lens and high-speed camera imaging system. In contrast to conventional imaging systems, the laser diffraction/scattering system is based on analyzing the diffraction pattern and scattering intensity, respectively, which provided higher resolution for micro-scale jetting measurement and enabled sub-micron level jetting correlation between the voltage applied to the electrode and printing results. Furthermore, Taylor cone information from the nozzle head could also be analyzed in real-time to make adjustments to the printing process. In this work, we successfully validated the feasibility of laser diffraction analysis in-situ monitoring for EHD inkjet printing at micron and sub-micron levels.

Study of the Flow Characteristics of Pumped Media in the Confined Morphology of a Ferrofluid Pump With Annular Microscale Constraints

Abstract The driving mechanism of ferrofluid micropumps under the constraints of an annular microscale morphology is not fully understood. The gap between microfabrication technology and the fundamental theory of microfluidics has become a substantial obstacle to the development and application of ferrofluid micropumps. In this study, we first theoretically analyzed the Knudsen numbers of millimeter-scale microfluids using Jacobson's molecular hard sphere model, obtaining the initial conclusion that liquid flow conforms to the continuum hypothesis in geometric morphologies with characteristic dimensions greater than 7 × 10−8 m. Subsequently, using a microscopic lens combined with the particle image velocimetry optical measurement method, the flow patterns in millimeter-scale annular flow channels were captured and we observed wall slip phenomena in which the slip length of the millimeter-scale channel approached the micron level. The slip velocity and flowrate through the cross section of the microscale channel followed a logarithmic function relationship and could be divided into rapid growth, slow growth, and stable stages. As the characteristic scale of the channel was further reduced, the linear relationship between the slip velocity and cross-sectional flowrate in the rapid growth stage was broken, and the nonlinear relationship approximated an exponential function. Finally, a theoretical model for the flow behavior of the driving fluid in a ferrofluid micropump was established using slip boundary conditions. The flow patterns in microscale ring flow under slip conditions conformed to a quadratic function.

Self-propagating high-temperature synthesis of AlN–TiC powder composition using sodium azide and C2F4 fluoroplastic

Producing powder compositions using conventional processing technology can lead to the formation of large agglomerates and, therefore, makes it difficult to obtain a uniform microstructure. The production of composites by self-propagating high-temperature synthesis can reduce costs and the number of technological stages, as well as lead to obtaining composites that are more homogeneous. Synthesis by the combustion of mixtures of powder reagents of sodium azide (NaN3), fluoroplastic (C2F4), aluminum and titanium with different ratios of reagents in a nitrogen gas atmosphere at a pressure of 4MPa was used for the production of a highly dispersed powder ceramic AlN–TiC composition. Thermodynamic calculations have confirmed the possibility of synthesis of AlN–TiC compositions of different formulations in combustion mode. The dependences of temperature and combustion rate on the composition of the initial mixtures of reagents were experimentally determined for all stoichiometric reaction equations. The study have shown that the experimentally found dependences of combustion parameters on the ratio of the initial components correspond to the theoretical results of thermodynamic calculations. The formulation of the synthesized composition differs from the theoretical composition by a lower content of target phases and the formation of Al2O3, Na3AlF6 and TiO2 side phases. The powder composition consists of aluminum nitride fibers with a diameter of 100–250nm and ultradisperse particles of predominantly equiaxed and lamellar shapes with a particle size of 200–600nm. As the combustion temperature increases to produce the largest amount of titanium carbide phase, the particle size increases to the micron level.

Self-Assembled Synthesis of Graphene Tubes from Melamine Catalyzed by Calcium Carbonate

This study investigates the carbon products generated by melamine under various heat-treatment temperatures with the catalysis of calcium carbonate. We discovered that the cost-effective precursor melamine readily self-assembles and curls into graphene tubes when catalyzed by the alkaline earth salt CaCO3 at elevated temperatures. Under heat-treatment conditions of 1100 °C and 1200 °C, the growth morphology of graphene tubes with open structures and exceptionally large diameters was observed, and the diameters reached the micron level. These products exhibit a high degree of carbonization and an extremely low nitrogen content, as low as 1.7%. Further, the intensity ratio (ID/IG) of the D band and the G band is as low as 0.79 in Raman characterization. The results show that the products have a certain graphite structure, which proves the catalytic activity of CaCO3. This is attributed to the incorporation of CaCO3 into the raw material system, which impedes the complete thermal decomposition of melamine. On the other hand, the resulting CaO particles are evenly distributed along the tubular products, providing certain support for their self-assembly and growth, thereby achieving the efficient growth of graphene tubes.

Online Inspection Method and System Design for Screw Threads of Rebar Head Based on Machine Vision

An online inspection method based on machine vision was proposed and validated to address the issues of high work intensity, low efficiency, low accuracy, and risk of missed inspection in traditional sampling methods for screw threads of rebar head. Firstly, an industrial camera was used to capture real-time images of the processed rebar thread heads, preprocess the images, and locate the target positions in the images to reduce the complexity and running time of subsequent algorithms. Then, the Canny operator was used to roughly extract the edge feature information of the rebar head, and the Shi–Tomasi algorithm was used for corner inspection to achieve precise optimization of sub-pixel level corners. Based on robust linear regression, the diagonal points were fitted with lines to detect the corresponding size parameters. Finally, an inspection system on screw threads of rebar head parameter was designed and developed, which consisted of an image-acquisition device, Siemens PLC controller, and inspection software. Test results show that this method can achieve online inspection without contact, with inspection accuracy reaching the micrometer level, and 8–10 rebar heads can be inspected per second.

A Nanosecond level current pulse capture taper optical fiber probe based on micron level NV color center diamond

Abstract This work demonstrates a micron-sized nanosecond current pulse probe using a quantum diamond magnetometer. A micron-sized diamond crystal affixed to a fiber tip is integrated on the end of a conical waveguide. We demonstrate real-time visualization of a single 100 nanosecond pulse and discrimination of two pulse trains of different frequencies with a coplanar waveguide and a home-made PCB circuits. This technique finds promising applications in the display of electronic stream and to be used as a pulse discriminator to Simultaneously receive and demodulate multiple pulse frequencies. This method of detecting pulse current is expected to provide further detailed analysis of the internal working state of the chip.

Multiphoton Lithography of Interpenetrating Polymer Networks for Tailored Microstructure Thermal and Micromechanical Properties.

Multiphoton lithography (MPL), an emerging truly 3D microfabrication technique, exhibits substantial potential in biomedical applications, including drug delivery and tissue engineering. Fabricated micro-objects are often expected to undergo shape morphing or bending of the entire structure or its parts. Furthermore, ensuring precise property tuning is detrimental to the realization of the functionality of MPL microstructures. Herein, novel MPL materials based on interpenetrating polymer networks (IPNs) are presented that effectively combine the advantages of acrylate and epoxy systems. IPNs with varying component ratios are investigated for their microfabrication performance and structural integrity with respect to thermal and micromechanical properties. A variety of high-resolution techniques is applied to comprehensively evaluate IPN properties at the bulk, micron, and segmental levels. This study shows that the MPL laser scanning velocity and power, photoinitiator content, and multi-step exposure can be used to tune the morphology and properties of the IPN. As a result, a library of 3D MPL IPN microstructures with high 3D structural stability and tailored thermal and micromechanical properties is achieved. New IPN microstructures with Young's moduli of 3-4MPa demonstrate high-to-fully elastic responses to deformations, making them promising for applications in morphable microsystems, soft micro-robotics, and cell engineering.

Microdosimetric measurements for LET monitoring in proton therapy. The development of engineered mini-TEPCs for clinical applications: First results

Innovative Treatment Planning Systems (TPS) in proton therapy based on a variable radiation quality with depth with respect to the conventional one with a fixed Relative Biological Effectiveness (RBE) of 1.1 are under study. Experimental methods are needed to verify the consistency between what is planned and what is delivered in terms of radiation quality. Microdosimetry studies the stochastics of the energy deposition process at micrometric and sub-micrometric level which is known to be related to the biological effectiveness of ionising radiation fields. For this reason, it is recognised by the scientific community that it is a useful tool to monitor the radiation quality of hadron therapy beams where the effectiveness varies with the penetration depth in patients. Detectors are needed to perform a microdosimetric characterization of a clinical beam and they need to satisfy specific requirements to enter the clinical practice as instruments for the Quality Assurance (QA). With this aim, at the Legnaro National Laboratories of the Italian National Institute for Nuclear Physics (LNL-INFN) a technological transfer project was carried out with the final goal of developing engineered miniaturized Tissue Equivalent Proportional Counters (mini-TEPCs) for clinical applications. This work presents the characterization performed on the new detectors and the results obtained in neutron and proton fields.

Design and Fabrication of High-Performance Piezoelectric Micromachined Ultrasonic Transducers Based on Aluminum Nitride Thin Films.

Ultrasound is widely applied in diverse domains, such as medical imaging, non-destructive evaluation, and acoustic communication. Piezoelectric micromachined ultrasonic transducers (PMUTs) capable of generating and receiving ultrasonic signals at the micrometer level have become a prominent technology in the field of ultrasound. It is important to enrich the models of the PMUTs to meet the varied applications. In this study, a series of PMUT devices featured with various top electrode configurations, square, circular, and doughnut, were designed to assess the influence of shape on the emission efficacy. It was demonstrated that the PMUTs with a circular top electrode were outperformed, which was calculated from the external acoustic pressure produced by the PMUTs operating in the fundamental resonant mode at a specified distance. Furthermore, the superior performance of PMUT arrays were exhibited through computational simulations for the circular top electrode geometries. Conventional microelectromechanical systems (MEMS) techniques were used to fabricate an array of PMUTs based on aluminum nitride (AlN) films. These findings make great contributions for enhancing the signal transmission sensitivity and bandwidth of PMUTs, which have significant potential in non-destructive testing and medical imaging applications.

In vivo confocal Raman spectroscopy: The window into the skin.

Development of invivo confocal Raman spectroscopy (ICRS) methodology over the last 20 years has enabled previously unavailable capability to acquire molecular concentration gradients across the stratum corneum (SC), at the micron level and in a clinical setting. Professor Tony Rawlings has been a driving force in SC research for over 30 years, working with a wide range of teams across the world. Because a detailed knowledge of skin biochemistry was key to interpreting ICRS-acquired molecular concentration gradients, the authors formed a close working relationship with Professor Rawlings during the development of ICRS. This article, therefore, presents a summary of this process and how challenges raised by application of ICRS were tackled, towards the goal of validating the technique for clinical skin measurement.

Cerium-based sorbent with 100% Ce(III) and high dispersion for enhanced phosphate removal from wastewater

Under the double pressure of eutrophication and phosphorus deficiency, there is an urgent need to remove excess phosphate from wastewater efficiently. Preparing cerium-based materials with excellent application potential inevitably leads to Ce(III) oxidation to Ce(IV), which reduces the phosphate adsorption effect and restricts its development. To solve this problem, we introduced a protective agent and successfully synthesised cerium-modified activated carbon sorbent containing 100 % Ce(III) during the synthesis process. Compared with CeAC without a protecting agent, CeAC-A contained more Ce(III) (100 %) and exchange groups (–OH accounted for 82.76 %), achieving an adsorption capacity of up to 448.57 mg-P/g Ce, improving of 4.3 times. At the same time, the size of the cerium active component was reduced from the micron level to the nanometer level, and the mass transfer rate was significantly improved. In addition, with the enormous specific surface area and well-developed pore structure of activated carbon, it showed high dispersibility, with P/Ce molar ratio as high as 2.03, which is 1.1–4.8 times higher than other cerium-based adsorbents. Phosphate was removed primarily through electrostatic attraction and ligand exchange. In treating municipal wastewater with complex water quality, CeAC-A showed strong selectivity, a wide range of adaptability and easy repeat regeneration, making it a promising adsorbent for phosphate uptake from wastewater.

Evaluating computational efforts and physiological resolution of mathematical models of cardiac tissue

Computational techniques have significantly advanced our understanding of cardiac electrophysiology, yet they have predominantly concentrated on averaged models that do not represent the intricate dynamics near individual cardiomyocytes. Recently, accurate models representing individual cells have gained popularity, enabling analysis of the electrophysiology at the micrometer level. Here, we evaluate five mathematical models to determine their computational efficiency and physiological fidelity. Our findings reveal that cell-based models introduced in recent literature offer both efficiency and precision for simulating small tissue samples (comprising thousands of cardiomyocytes). Conversely, the traditional bidomain model and its simplified counterpart, the monodomain model, are more appropriate for larger tissue masses (encompassing millions to billions of cardiomyocytes). For simulations requiring detailed parameter variations along individual cell membranes, the EMI model emerges as the only viable choice. This model distinctively accounts for the extracellular (E), membrane (M), and intracellular (I) spaces, providing a comprehensive framework for detailed studies. Nonetheless, the EMI model’s applicability to large-scale tissues is limited by its substantial computational demands for subcellular resolution.

Structural and molecular characterization of astrocyte and vasculature connectivity in the mouse hippocampus and cortex.

The relation of astrocytic endfeet to the vasculature plays a key functional role in the neuro-glia-vasculature unit. We characterize the spatial organization of astrocytes and the structural aspects that facilitate their involvement in molecular exchanges. Using double transgenic mice, we performed co-immunostaining, confocal microscopy, and three-dimensional digital segmentation to investigate the biophysical and molecular organization of astrocytes and their intricate endfoot network at the micrometer level in the isocortex and hippocampus. The results showed that hippocampal astrocytes had smaller territories, reduced endfoot dimensions, and fewer contacts with blood vessels compared with those in the isocortex. Additionally, we found that both connexins 43 and 30 have a higher density in the endfoot and the former is overexpressed relative to the latter. However, due to the limitations of the method, further studies are needed to determine the exact localization on the endfoot. The quantitative information obtained in this study will be useful for modeling the interactions of astrocytes with the vasculature.

Flame synthesis of nanoparticles based on high flux electrostatic atomization burner.

This study presents an innovative electrostatic spray flame synthesis (ESFS) reactor that combines the advantages of electrostatic spray and flame synthesis for precise spray control and efficient single-step continuous synthesis. To overcome the limitations of conventional ESFS systems, which often suffer from low atomized precursor flux, we successfully demonstrated a high-flux disk electrostatic atomizer coupled low-swirl flame reactor, achieving a precursor flux of up to 30 ml/h about 30 times higher than that of typical ESFS devices. The atomized precursor being rapidly carried away from the burner is undergoing high-temperature pyrolysis and particle formation through lifted premixed turbulent flames. The ESFS system provides extensive control over parameters such as flame temperature, equivalence ratio, residence time, initial droplet sizes, and precursor concentrations. For illustrative purposes, the ESFS system was utilized to synthesize silica nanoparticles, demonstrating the capability of synthesizing nanoparticles with various properties. By manipulating the collection position and height, the particle size has made a substantial leap from the nanoscale to the micrometer level. This remarkable achievement underscores the system's enormous potential for precise particle size regulation and one-step synthesis of complex structured thin films.

Size tuning of vanadium nitride particles from atomic to micron level as efficient catalysts for zinc-air battery

Transition metal nitrides present superior electrocatalytic activities on the air electrode for fuel cells or metal-air batteries. Despite that, the weak intrinsic activity and ease of aggregation have hampered their catalytic kinetic properties and practical application. Herein, vanadium nitride (VN) particles of different sizes, micron to molecular level, have been fabricated using a facile, in-situ urea-nitridation method, and embedded in an N-doped graphitic carbon aerogel electrocatalyst (VN@CA), the doped material serving as an oxidation catalyst. Having a balance of atomic-level dispersed VN clusters and a high active site density, the obtained VN@CA catalytic material exhibits enhanced catalytic efficiency for the oxygen reduction reaction (ORR), the values of onset and half-wave voltages were measured to be 0.97 V and 0.90 V, respectively, compared to Pt/C (which had voltages of 0.95 V and 0.87 V). Furthermore, the assembled Zn-air battery using VN@CA as catalyst exhibits a high-power density of 176 mW cm−2, a substantial specific discharge capacity of 851 mAh gZn−1 at 20 mA cm−2, a narrow gap between charging and discharging voltages (0.73 V at 50 mA cm−2), and an excellent charge-discharge cycling stability, exceeding 270 cycles with a 66 % round-trip efficiency. This work confirms that the particle size and the density both are responsible for the enhanced electrochemical activity.

Fabrication of Large-Area Nanostructures Using Cross-Nanoimprint Strategy.

Nanostructures with sufficiently large areas are necessary for the development of practical devices. Current efforts to fabricate large-area nanostructures using step-and-repeat nanoimprint lithography, however, result in either wide seams or low efficiency due to ultraviolet light leakage and the overflow of imprint resin. In this study, we propose an efficient method for large-area nanostructure fabrication using step-and-repeat nanoimprint lithography with a composite mold. The composite mold consists of a quartz support layer, a soft polydimethylsiloxane buffer layer, and multiple intermediate polymer stamps arranged in a cross pattern. The distance between the adjacent stamp pattern areas is equal to the width of the pattern area. This design combines the high imprinting precision of hard molds with the uniform large-area imprinting offered by soft molds. In this experiment, we utilized a composite mold consisting of three sub-molds combined with a cross-nanoimprint strategy to create large-area nanostructures measuring 5 mm × 30 mm on a silicon substrate, with the minimum linewidth of the structure being 100 nm. Compared with traditional step-and-flash nanoimprint lithography, the present method enhances manufacturing efficiency and generates large-area patterns with seam errors only at the micron level. This research could help advance micro-nano optics, flexible electronics, optical communication, and biomedicine studies.

Plastic Waste Identification Using Deep Learning for Adequate Waste Management

Plastic waste management has emerged as a critical global challenge, prompting concerted efforts from conservation authorities and international organizations like the United Nations to enhance detection and classification strategies. This research distinguishes itself by harnessing advanced deep learning techniques to identify plastic materials at the micron level, surpassing traditional macro-level methods. The primary goal is to classify plastics into four major distinctions, addressing a key challenge in plastic segregation by accurately measuring thickness. Leveraging the YOLOv8 architecture, this approach enables precise classification of plastics into Polyethylene terephthalate (PETE), High Density Polyethylene (HDPE), low density polyethylene (LDPE0, and Polyvinyl Chloride (PVC) categories based on thickness. To achieve this, incorporation of hardware components such as ultrasonic sensors and NodeMCU for detecting thickness variations is used. By facilitating effective segregation according to environmental impact, this innovation revolutionizes waste reduction efforts, offering real-time identification and enhancing overall sustainability in plastic waste management.