Micrometer Scale Research Articles

Experimental and numerical investigation of water flow in different media models at multiple scales

ABSTRACT The study of the flow behavior in pores, fractures, and pore-fracture dual media plays a crucial role in understanding the mechanisms of sudden water inrush and sand flow. In this study, laboratory experiments were conducted using a custom-made transparent porous model to investigate the flow characteristics of fluids in complex media. Additionally, finite element simulations were employed to explore the flow features at multiple scales. A detailed analysis at the micrometer scale was conducted to examine the variations in the water velocity, volumetric flow rate, Reynolds number, flow field, and permeability under different porosity and pressure drop conditions. The results indicate that within the studied range of flow velocities and pressures, the fluid flow in all the media models adhered to Darcy’s law. The improvement in structural connectivity in the random pore model has made the flow channels of fluids in the random pore network more diverse, resulting in an increase in the peak water flow velocity from 4.89E–5 m/s to 4.19E–4 m/s. The fluid accelerated while bypassing the protruding solid particles, resulting in the formation of high-velocity zones in the vicinity. As the pressure drop increases, the volume flow rate of the random dual-medium model with a porosity of 0.6 can increase to 1.01E–9 m3/s, with the highest growth rate. We also simulate the fluid flow of a regular dual-medium model at different porosities and find that the permeability rapidly increases from 5.65E–13 m2 to 1.01E–11 m2, demonstrating that the presence of fractures can significantly improve the permeability performance of the medium. The research findings deepen our understanding of the migration behavior of water in complex geological environments and provide theoretical guidance for groundwater resource protection and underground engineering.

Multi-Scale Characterization of Pores and Fractures in Coals with Different Coal-Body Structures from the Jincheng Mine, Qinshui Basin, Northern China

The Qinshui Basin is located in the southeast of Shanxi Province, China. It is one of the most abundant coal resources from Permo-Carboniferous North China. It is rich in coal and coalbed methane resources. However, the accumulation of coalbed methane is complex and the enrichment law has not been fully understood because of the high heterogeneity of coal reservoirs in the Qinshui Basin. The examination of dissimilarities between tectonically deformed coals (TDCs) and primary coals at multiple scales holds paramount importance in advancing our understanding of the occurrence and flow patterns of coalbed methane, and in providing guidance for exploration efforts. In the present study, the samples from the Jincheng Mine, Qinshui Basin, were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP), CO2 gas adsorption and 3D X-ray micro-computed tomography. The results showed that the dominant minerals in coal were illite, kaolinite, and calcite, with minor amounts of quartz and ankerite. In comparison to primary coal, tectonism could increase the microfractures density of type A (the fracture of width ≥ 5 μm and length > 10 mm) in TDCs. In CO2 gas adsorption in mylonite coal, it was observed that the volume of micropores (<2 nm) was significantly reduced leading to a decrease in gas adsorption capacity. The result of Micro-CT scanning revealed that the minerals occurred as veins in primary coal, but as irregular aggregates in TDCs. Moreover, tectonism had a staged impact on fracture structure, which was initially closed in cataclastic coal and then formed into granulated coal during the tectonic evolution. The effects of tectonism on coal structure had an impact on the connectivity of micropores at the micrometer scale by the destruction of the pore throat structure, increasing the heterogeneity of the reservoir. These findings help to better understand the changes in TDC structure at different scales for developing effective strategies for coalbed methane exploration and production.

Microanalytical approaches on the silicification process of wood fossil from Jasinga, West Java, Indonesia

Worldwide, silicified woods are found in many geological formations. Significantly, the organic materials of wood are no longer dominant; almost all wood fossils have been mineralized into inorganic silica materials. These unique geological processes must be understood to develop better understanding on organic material fossilization, particularly in the micron scale. Therefore, our aim was to characterize the composition of silicified wood using comprehensive microanalysis. The methods utilized were XRF, ICP-MS, XRD, FTIR, and FE-EPMA. Specimens are from Jasinga, West Java, Indonesia. The results showed that wood silicification was controlled by the infiltration of silica from the host rock into the spaces of the wood structure. In Jasinga, they are controlled by Pliocene tuffaceous sedimentary rocks. The ratio of silica phases revealed a trend in the degree of silicification. Besides silica, the distribution of trace elements also demonstrates the geochemical interaction between the wood fossil and host rock. Wood fossils are affected by the gradual replacement of organic carbon-based materials with silica through silicification. Silica enrichment occurs in the internal of wood, facilitates permineralization and recrystallization. Silica replaces organic material and preserves the wood structures. The microanalytical approach provides comprehensive perspectives on wood petrification, leads to better insights for paleontological studies.

Modeling stable cavitation of coated microbubbles: A framework integrating smoothed dissipative particle dynamics and the Rayleigh-Plesset equation.

Coated microbubbles are widely used in medical applications, particularly in enhanced drug and gene delivery. One of the mechanisms underlying these applications involves the shear stress exerted on the cell membrane by acoustic microstreaming generated through cavitation bubbles. In this study, we develop a novel simulation approach that combines the smooth dissipative particle dynamics (SDPD) simulation method with numerical modeling of the Rayleigh-Plesset-like equation in an ad hoc manner to simulate stable cavitation of microbubbles at microsecond and micrometer scales. Specifically, the SDPD method is utilized to model fluid dynamics, while the Rayleigh-Plesset-like equation is employed to describe bubble dynamics. Adopting a 1.5 μm coated microbubble driven by ultrasound with a frequency of 2MHz and a pressure of 500kPa as a representative example, we observe a high-velocity microstreaming pattern emerging around the bubble on a very small scale of a few micrometers after only a few microseconds. These spatiotemporal scales may pose challenges for experimental observation. The formation of this microstreaming arises from the opposing motion of the fluid layer next to the bubble and the fluid layers further away. Furthermore, our simulations reveal high shear stress levels of thousands of Pascals exerted on a wall located a few micrometers from the bubble. This contrasts with the shear stress values of a few Pascals calculated from theoretical models in the literature, which do not incorporate radial streaming into their theories. The implications of our results for bubble cavitation-induced pore formation on the cell membrane are discussed in some details.

Study on plasma modified silica powder epoxy resin composites

This work uses micrometer scale silicon powder as raw material, conducts plasma interface modification in a nitrogen atmosphere, and adds nitrogen elements to generate active groups such as amino groups on its surface to improve the dispersion of silicon powder, enhance the interface interaction between silicon powder and epoxy resin, and form Si–N bonds. To a certain extent, the absorption performance of silicon powder has been improved, which indicates the effectiveness of plasma modification of Si powder. The hardness of the modified composite material increased from 75.52 to 85.34 HA. Mechanical experiments have shown that the addition of 3% wt significantly improves the tensile strength of epoxy resin, increasing it from 16.47 to 22.67 Mpa. Further increase in dosage will lead to a decrease in tensile strength. After modification, the 3%, 5%, and 10% modified epoxy composite materials increased from 22.67, 9.94, and 5.67 Mpa before modification to 24.15, 14.52, and 12.75 Mpa, respectively. Using molecular dynamics simulation to verify the feasibility of plasma modification on epoxy composite materials, it was found that the simulation results were consistent with the experimental results, and the ultimate tensile strength of the modified composite materials was improved. The electrochemical impedance spectroscopy and salt spray test results show that the low-frequency impedance modulus of the composite coating modified by plasma interface is about one order of magnitude higher than that of the unmodified silicon powder composite coating. The coating containing 5 wt% plasma modified silicon powder exhibits the best corrosion resistance.

Taxis-enhanced mineralization and co-metabolism of PAHs by bacteria in micrometer-scale environments

Polycyclic aromatic hydrocarbons (PAHs) are associated with micropores in sediments and soils. This limits the bioaccessibility of these compounds via existing bioremediation technologies, as biodegradation is strongly influenced by the ability of bacteria to access different sizes of pores. In this work, we employed naphthalene and pyrene as model contaminants to evaluate the transformation capacity of the soil bacterium Pseudomonas putida G7 (2 × 1 μm) via mineralization and co-metabolic activity, respectively. Under non-growing conditions and in the absence of hydraulic flow, we examined how the tactic behavior of this motile bacterium influenced biodegradation of these two PAHs when passing through membranes with micrometer-sized pores (3 and 5 μm). The bacteria were spontaneously retained by the membranes, which blocked the contaminants away from a passive dosing source. However, the cells were mobilized through 5 μm pores after the application plant root exudate components (γ-aminobutyric acid, citrate and fructose) as strong chemoeffectors, which enhanced the mineralization of naphthalene and co-metabolism of pyrene. The tactic-mediated biodegradation enhancement did not occur through 3 μm pores, possibly due a physical constrain to the gradient sensing mechanism. Our results suggest that bacterial transport by chemotaxis may enhance the biotransformation of poorly bioaccessible contaminants present in micro-meter scale environments.

Chemical Patterning of Graphene, Graphite and MoS2: From Microscale to Nanoscale

Chemical patterning of 2D materials is relevant in several different domains of science and technology with exciting possibilities in electronics, catalysis, sensing, and photonics. Despite intense efforts, spatially controlled, (multifunctional) covalent chemical patterning of graphene and related 2D materials is not straightforward. In my talk, I will present examples of covalent chemical patterning of graphene, graphite and MoS2 using diazonium chemistry. In the first case, spatially resolved multicomponent covalent chemical patterning of single layer graphene was achieved using a facile and efficient method. Three different functional groups could be covalently attached to the basal plane in dense, well-defined micrometer wide patterns using a combination of lithography and a self-limiting variant of diazonium chemistry requiring no need for graphene activation. The layer thickness of the covalent films could be controlled down to 1 nm. In the second case, i will present sub-10 nm chemical patterning of graphite achieved using the electrochemical diazonium chemistry. Here, an elegant combination of covalent and non-covalent chemistry was used to achieve 5-6 nm wide linear chemical patterns with excellent pattern transfer fidelity. In the last example, I will briefly share our initial results on the nanoscale chemical patterning of MoS2 using electrochemical diazonium chemistry. Throughout the discussion, i will highlight the critical role of scanning probe microscopy, namely STM, AFM and AFM-IR in providing critical spatial and spatio-chemical information at the nano and micrometer scale where conventional analytical techniques fail to provide accurate information.

Noise Interrogation during an Induced Faradaic Reaction

Single-entity electrochemistry has emerged as a potent method that allows for examination of individual responses within a system to comprehend a bulk response. For example, utilizing electrodes on the micrometer scale or smaller provides the requisite sensitivity to discern the impact of a nanoparticle contacting the electrode surface which catalyzes a reaction. Nevertheless, the detection of nanoimpacts is limited by the presence of noise which stems from the inherent non-inert nature of electrodes.Understanding the noise level under a continuous Faradaic reaction becomes crucial for detecting catalysis at the sub-micron scale. In this presentation, I will describe how we understand and quantify the level of noise under diverse conditions. We measured noise while varying electrode size, sampling frequency, and redox-probe concentration. These results allowed us to formulate a model to predict noise at an electrode. Commonly, noise is thought to scale with the square root of current. However, our measurements reveal that the background noise level shifts from a square root dependence at the macroscale to a linear dependence at the microscale. Moreover, a chemically-coupled reaction (EC’) produces lower noise in comparison with a purely electrochemical reaction that produces the same steady-state current. In combination, these results suggest that diffusion partially dictates the amount of noise, along with the amount of redox-active species exchanging charge with the electrode. By understanding these noise sources, we may begin to control them, yielding more accurate and precise single-entity results.

(Invited) Electrode Transport Resistance Analysis in Proton Exchange Membrane Water Electrolyzers

Decarbonizing sectors that are challenging and economically demanding to electrify, such as heavy-duty ground transportation, aviation, and industries like ammonia, steel, petroleum refining, synthetic fuels, and cement production, is crucial in addressing climate change and environmental pollution. The key strategy for reducing the reliance of these sectors on fossil fuels and cutting emissions involves utilizing hydrogen with low carbon intensity. Proton exchange membrane water electrolyzers (PEMWEs) play a vital role in this transition due to their high efficiency, rapid response time, and capability to electrochemically compress hydrogen. However, despite making encouraging progress, significant improvements in catalyst activity and utilization are necessary to lower loadings to levels that meet ambitious cost targets.One critical aspect of enhancing catalyst performance for achieving high currents at efficient low voltages is minimizing overpotential losses. These losses result from electron, proton, and water transport to the oxygen evolution catalysts. Additionally, there are secondary current-induced loss mechanisms, including membrane and electrode dry-out and ionic contaminant polarization.In this presentation, we will delve into the relevant transport mechanisms and the fundamental limits of reducing these overpotentials through modeling. We have evaluated the transport properties of electrodes that are challenging to directly probe due to their micrometer and sub-micrometer length scales using ultra-high-resolution three-dimensional imaging with X-ray computed tomography (nano-CT) and plasma-focused ion beam cross-sectioning with scanning electron microscopy (pFIB-SEM) for image-based simulations. Subsequently, we will briefly review existing methods for experimentally diagnosing transport limitations, as well as highlight new methods currently under development in our laboratory. These new diagnostics include a galvanostatic intermittent titration technique (GITT) for electrolyzers and a limiting-current diagnostic for PEMWEs. The presentation will conclude by highlighting fresh insights into the significance of two-phase transport, electrode and membrane dry-out, all enabled by these diagnostics and modeling.

The Importance of Adhesion in Solid-State Batteries

Solid-state batteries are one of the key technologies to expedite the electrification of the economy. Compared with traditional liquid electrolytes, solid-state electrolytes are intrinsically safer and can enable high-energy designs by pairing with high-capacity cathodes and lithium metal anodes. However, maintaining the solid/solid contact between electrode and electrolyte during electrochemical cycling is non-trivial and the main challenge for all-solid-state batteries. The common strategy for combatting the contact issue is applying stack pressure, which is a sort of scientific shortcut that masks the real challenges of maintaining good contact between the different electrodes and electrolytes. Improving the adhesion between different battery components is a more effective and commercially viable strategy. We hypothesized that increasing the adhesion between electrode and electrolyte will improve electrode integrity, mitigate contact loss, and increase Coulombic efficiency and cycle life.There are very few studies on the adhesion of battery materials. This is primarily due to limited techniques to measure adhesion at the nanometer and micrometer scales relevant to the battery operation. In this work, we proposed to use atomic force microscopy (AFM) with customized probes to investigate adhesion between a model solid polymer electrolyte (SPE) consisting of crosslinked poly(ethylene oxide) (xPEO) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and a model cathode active material, LiNi0.6Mn0.2Co0.2O2 (NMC622). We showed that a two-fold increase in polymer stiffness (storage shear modulus, G’) from increasing the crosslinking density, leads to a 40% reduction in the bulk ionic conductivity in the SPE. However, we show evidence that this trade-off relationship between stiffness and ionic conductivity does not significantly impact the battery performance. In drastic contrast, it leads to a decrease in the work of adhesion at the electrolyte|cathode interface, which has a profound impact on the resulting discharge capacity of the battery. How the crosslinking density of the polymer affects the NMC-xPEO adhesion at the microscale and how this affects battery performance remain open questions, which the authors wish to gain insight into from the discussions.

Topographic Measurement of the Subretinal Pigment Epithelium Space in Normal Aging and Age-Related Macular Degeneration Using High-Resolution OCT.

A micrometer scale hyporeflective band within the retinal pigment epithelium basal lamina - Bruch's membrane complex (RPE-BL-BrM) was topographically measured in aging and age-related macular degeneration (AMD). In a prospective cross-sectional study, 90 normal eyes from 76 subjects (range = 23-90 years) and 53 dry AMD eyes from 47 subjects (range = 62-91 years) were enrolled. Isotropic volume raster scans over 6mm × 6mm (500 × 500 A-scans) were acquired using a high-resolution (2.7 µm axial resolution) spectral-domain optical coherence tomography (SD-OCT) prototype instrument. Six consecutive optical coherence tomography (OCT) volumes were computationally motion-corrected and fused to improve feature visibility. A boundary regression neural network was developed to measure hyporeflective band thickness. Topographic dependence was evaluated over a 6-mm-diameter Early Treatment Diabetic Retinopathy Study (ETDRS) grid. The hyporeflective band thickness map (median of 4.3 µm and 7.8 µm in normal and AMD eyes, respectively) is thicker below and radially symmetric around the fovea. In normal eyes, age-associated differences occur within 0.7 to 2.3mm from the foveal center (P < 0.05). In AMD eyes, the hyporeflective band is hypothesized to be basal laminar deposits (BLamDs) and is thicker within the 3-mm ETDRS circle (P < 0.0002) compared with normal eyes. The inner ring is the most sensitive location to detect age versus AMD-associated changes within the RPE-BL-BrM. AMD eyes with subretinal drusenoid deposits (SDDs) have a significantly thicker hyporeflective band (P < 0.001) than those without SDDs. The hyporeflective band is a quantifiable biomarker which differentiates AMD from aging. Longitudinal studies are warranted. The hyporeflective band may be a useful biomarker for risk stratification and disease progression.

Synchrotron Infrared Nano-Spectroscopy and Imaging of Lithium Fluoride in the Solid Electrolyte Interphase on Li-Ion Anodes

The solid electrolyte interphase layer that forms on the surface of the negative electrode in Li-ion batteries is crucial for battery cycle/calendar life, rate performance and safety. This 10's of nanometers layer is formed from the decomposition of the liquid electrolyte and its passivation properties are very sensitive to its formation and aging conditions. Despite this critical role, there is still a lack of fundamental understanding of how its structure and composition relate to its stability and passivation performance.Amongst the SEI products that form during the decomposition of liquid electrolyte, lithium fluoride (LiF) is a ubiquitous component and many attribute its presence to be a determining factor of a well passivated interface. Despite the importance, LiF’s nanostructure and distribution within the SEI layer is rarely investigated due to the lack of suitable characterization techniques. X-ray photoelectron spectroscopy (XPS) is the main tool to identify LiF in the SEI layer, but its micron scale lateral resolution precludes any nanometer scale mapping of LiF’s distribution which limits its ability to identify the role LiF plays in the SEI layer.Recently our group has been characterizing the SEI layer of Li-ion negative electrodes with nano-Fourier transform infrared spectroscopy (nano-FTIR).1,2 Nano-FTIR is a scanning probe technique based in a typical atomic force microscope (AFM) in which a broadband laser illuminates a metallic tip/sample interface. The metallic tip acts as an antenna, focusing the infrared light adjacent to the interface and creating a near-field interaction. By operating in constant tapping mode and due to the nonlinearity of the near-field signal on the tip/sample distance, the corresponding backscattered light from the near-field interaction with the sample can be separated from the background with lock-in amplification. The result is IR reflection and absorption spectra with lateral resolution close to the tip radius (ca. 20 nm). This far exceeds the diffraction limited resolution of typical IR microscopy (~10’s µm) creating new opportunities for IR characterization on nanometer length scales.In this talk, we’ll discuss our recent work related to utilizing synchrotron-based nano-FTIR to characterize and image LiF in the SEI layer of Li-ion based negative electrodes. The synchrotron infrared light source allows the detection of photons out to the far-IR (322 cm-1 limit) which enables the detection of the vibrational modes of Li containing inorganic phases such as LiF, Li2O, and LiH. By comparing model thin film LiF nano-FTIR spectra with experimental spectra take from the surfaces of Cu, Si thin film, and a novel metallic glass anode, we can gauge the heterogeneity of the LiF in the SEI layer and then suggest different LiF formation mechanisms. Based on the results, we believe that nano-FTIR with a synchrotron based light source will be a key tool to unravelling the nanoscale structure of the SEI layer due to its nanoscale chemical sensitivity and nondestructive nature.This research was supported by the US Department of Energy (DOE)’s Vehicle Technologies Office under the Silicon Consortium Project directed by Brian Cunningham and managed by Anthony Burrell. This research used resources of the Advanced Light Source from beamline 2.4, which is a DOE Office of Science User Facility under contract no. DE-AC02-05CH11231. References (1) Dopilka, A.; Gu, Y.; Larson, J. M.; Zorba, V.; Kostecki, R. Nano-FTIR Spectroscopy of the Solid Electrolyte Interphase Layer on a Thin-Film Silicon Li-Ion Anode. ACS Appl. Mater. Interfaces 2023, 15 (5), 6755–6767.(2) He, X.; Larson, J. M.; Bechtel, H. A.; Kostecki, R. In Situ Infrared Nanospectroscopy of the Local Processes at the Li/Polymer Electrolyte Interface. Nature Communications 2022, 13 (1), 1398.

Bessel beam propagation using radial beam propagation method at different propagation scales

This paper is devoted to studying the Bessel beam propagation in cylindrical coordinates using the Hankel transform beam propagation method (HT-BPM) and their behavior in different scenarios in the microscale and meter scale of propagation distances. The study compares the results obtained from the HT-BPM with another fast Fourier transform beam propagation method (FFT-BPM) to validate the accuracy and effectiveness of the HT-BPM in modeling Bessel beam propagation. The axial intensity of Bessel beam propagation is analyzed using the HT-BPM. The simulation results obtained from the HT-BPM are compared with those from the FFT-BPM to evaluate the agreement and consistency between the two methods in predicting the axial intensity of Bessel beam propagation. The results show that the HT-BPM is numerically faster than the FFT-BPM by ten times for different sampling points, furthermore, the FFT-BPM accuracy for evaluating the Bessel beam spot radius is 89.9% of the analytical value, while the HT-BPM is 99% relative to analytical value. The prediction of the axial intensity of the Bessel beam has been tested at different types of phase functions and different propagation distances: micrometer, centimeter, and meter scales. The results of the HT-BPM are matched with the analytical and experimental values. Finally, the HT-BPM is tested when the input light source takes different profiles.

Ultra Low Power Consumption Optoelectronic Logic Operation of CuO/BaTiO3 Heterojunction Photodetector with Tunable Internal Electric Field Based on Poling Effect

AbstractThe study presents a novel self‐powered ultraviolet (UV) photodetector harnessing both polarization fields and photovoltaic effects, enabling the realization of ultra‐low power, reconfigurable optoelectronic logic gates. The approach is demonstrated on a CuO/BaTiO3 heterojunction photodetector. The behavior of the photodetector is augmented by the poling effect, aligning the internal electric field of the BaTiO3 through the application of a robust external electric field, thereby facilitating the implementation of optoelectronic logic gates. In the unpoled state, the “XOR” and “OR” logic gates operated at voltages of 750 and −500 µV, respectively. However, upon poling up state, the “XOR” logic gate exhibits reduced operation voltage, operating at 500 µV, while the “OR” logic gate implements clarity at −500 µV. In the unpoled state the “AND” logic gate does not operate; however, upon poling in the downward direction, it operated at −500 µV. The achievement demonstrates successful ultra‐low‐power logic operations, utilizing voltages in the hundreds of micron scale, under a 310 nm wavelength and a light intensity of 0.52 mW·cm−2. Furthermore, controllable polarization electric fields in BaTiO3 enable the operation of “AND” logic gate in the unpoled state, presenting a promising avenue for future research in optoelectronic logic gate design.

Quantitative Measurement of Multiple Elements in Micro‐Quantities of Crude Oil Using In Situ Analysis by Laser Ablation‐ICP‐MS

Multi‐element quantification in small amounts of material and in situ measurements at the micrometre scale are essential aspects of geological sample investigation. A direct and rapid simultaneous multi‐elemental determination of metals in crude oil samples was carried out by combining direct laser ablation of the oil inserted in silica capillaries with inductively coupled plasma‐mass spectrometry. The accuracy of LA‐ICP‐MS determination was demonstrated by analysing CONOSTAN reference material oils, certified for multiple elements, and by comparing LA‐ICP‐MS measurement results with those obtained by ICP‐OES using microwave‐assisted sample digestion. The results obtained by both methods were in agreement with certified values. The LA‐ICP‐MS method showed an adequate precision with a mean relative standard deviation of less than 10% for multi‐element determination, and was sufficiently sensitive to determine the majority of elements. LA‐ICP‐MS was also applied to the determination of elements in crude oils of different origins. LA‐ICP‐MS is a good alternative method allowing the determination of elements in organic fluids (oil and bitumen) in shorter times, involving less material consumption, smaller test portion size and with higher throughput compared with protocols using, for instance, sample digestion. It validates the possible application of metal analysis in hydrocarbon‐containing fluid inclusions for metallogenic purposes.

Supercritical Fluids: An Innovative Strategy for Drug Development.

Nanotechnology plays a pivotal role in the biomedical field, especially in the synthesis and regulation of drug particle size. Reducing drug particles to the micron or nanometer scale can enhance bioavailability. Supercritical fluid technology, as a green drug development strategy, is expected to resolve the challenges of thermal degradation, uneven particle size, and organic solvent residue faced by traditional methods such as milling and crystallization. This paper provides an insight into the application of super-stable homogeneous intermix formulating technology (SHIFT) and super-table pure-nanomedicine formulation technology (SPFT) developed based on supercritical fluids for drug dispersion and micronization. These technologies significantly enhance the solubility and permeability of hydrophobic drugs by controlling the particle size and morphology, and the modified drugs show excellent therapeutic efficacy in the treatment of hepatocellular carcinoma, pathological scarring, and corneal neovascularization, and their performance and efficacy are highlighted when administered through multiple routes of administration. Overall, supercritical fluids have opened a green and efficient pathway for clinical drug development, which is expected to reduce side effects and enhance therapeutic efficacy.

Quantifying trapping stability of optical tweezers with an external flow

Optical tweezers (OTs) can immobilize and manipulate objects with sizes that span between nano- and micro-meter scales. The manipulating ability of OTs is traditionally characterized by stability factor (S), which can only indicate an empirical “hit-or-miss” process. Additionally, the current quantitative models for trapping stability rarely consider the influence of external flow. In this paper, a comprehensive analysis to quantify the optical trapping stability in a perturbed asymmetric potential well is presented from the perspective of statistics, especially for weak trapping scenarios. Our analytical formulation takes experimentally measurable parameters including particle size, optical power, and spot width as inputs and precisely outputs a statistically relevant mean trapping time. Importantly, this formulation takes into account general and realistic cases including fluidic flow velocity and other perturbations. To verify the model, a back-focal-plane-interferometer-monitored trapping experiment in a flow is set up and the statistical characteristics of trapping time demonstrate good agreement with theoretical predictions. In total, the model quantitatively reveals the effects of external disturbance on trapping time, which will find applications where optical trapping stability is challenged by external perturbations in weak trapping conditions.

Differential association of key bacterial groups with diatoms and Phaeocystis spp. during spring blooms in the Southern Ocean.

Interactions between phytoplankton and heterotrophic bacteria significantly influence the cycling of organic carbon in the ocean, with many of these interactions occurring at the micrometer scale. We explored potential associations between specific phytoplankton and bacteria in two size fractions, 0.8-3 µm and larger than 3 µm, at three naturally iron-fertilized stations and one high nutrient low chlorophyll station in the Southern Ocean. The composition of phytoplankton and bacterial communities was determined by sequencing the rbcL gene and 16S rRNA gene from DNA and RNA extracts, which represent presence and potential activity, respectively. Diatoms, particularly Thalassiosira, contributed significantly to the DNA sequences in the larger size fractions, while haptophytes were dominant in the smaller size fraction. Correlation analysis between the most abundant phytoplankton and bacterial operational taxonomic units revealed strong correlations between Phaeocystis and picoeukaryotes with SAR11, SAR116, Magnetospira, and Planktomarina. In contrast, most Thalassiosira operational taxonomic units showed the highest correlations with Polaribacter, Sulfitobacteria, Erythrobacter, and Sphingobium, while Fragilariopsis, Haslea, and Thalassionema were correlated with OM60, Fluviicola, and Ulvibacter. Our in-situ observations suggest distinct associations between phytoplankton and bacterial taxa, which could play crucial roles in nutrient cycling in the Southern Ocean.

Analysis of atomization characteristics and efficient synthesis of Mg(OH)2 in micron scale atomization reactor

Analysis of atomization characteristics and efficient synthesis of Mg(OH)2 in micron scale atomization reactor

Enhancing Gelatine Hydrogel Robustness with Sacran-Aldehyde: A Natural Cross-Linker Approach

Tunable hydrogels have gained significant attention in the bioengineering field due to their designer preparation approach. Towards this end, gelatine stands out as a promising candidate owing to its desirable attributes, such as biocompatibility, ability to support cell adhesion and proliferation, biodegradability, and cost-effectiveness. This study presents the preparation of a robust gelatine hydrogel employing sacran aldehyde (SDA) as a natural cross-linker. The resulting SDA-cross-linked gelatine hydrogels (GSDA) display an optimal compressive stress of 0.15 MPa at 50% strain, five times higher than pure gelatine hydrogel. As SDA cross-linking concentration is increased, the swelling capacity of GSDA declines. This decline in swelling capacity, from 80% to 40%, is a result of strong crosslinking of gelatin with SDA. Probing further with FT-IR spectroscopy and SEM at the micron scale unveiled a dual-cross-linking mechanism within the hydrogels. This mechanism encompasses both short- and long-range covalent cross-linking, along with thermo-induced physical cross-linking, resulting in a significant enhancement of the load-bearing capacity of the fabricated hydrogels.