Micrometer Scale Research Articles

Probing structural modification of milk proteins in the presence of pepsin and/or acid using small- and ultra-small-angle neutron scattering

Acid- and pepsin-induced milk protein coagulation plays a crucial role in the gastric digestion of milk. Real-time structural evolution at a nano- (e.g. colloidal calcium phosphate (CCP) and micelle) and micro- (gel network) level of unheated and heated (85 °C for 30 min) bovine milk was examined under acidic conditions and at low and high concentrations of pepsin using ultra-small- and small-angle neutron scattering (USANS and SANS), small-amplitude oscillatory rheometry and confocal scanning laser microscopy. Milk was treated with glucono-δ-lactone (GDL), pepsin or a combination of GDL and pepsin to induce coagulation. Heat-treated milk showed a faster increase in elastic storage modulus (G′) and scattering intensity (USANS and SANS) compared with unheated milk when coagulated with GDL or the combination of GDL and pepsin. At pH 6.3, heat treatment retarded pepsin (1.10 U/mL)-induced milk coagulation, with slower increases in G′ and scattering intensity. At a high concentration of pepsin (2000 U/mL) that mimics the concentration found in the stomach, general proteolysis followed coagulation. Heat treatment retarded coagulation but accelerated curd proteolysis. This study demonstrates how time-resolved USANS and SANS can be used to investigate the structural evolution of protein coagulation and degradation under gastric environment conditions at nano- and micro-metre length scales.

Nucleation limited assembly and polarized growth of a de novo-designed allosterically modulatable protein filament.

The design of inducibly assembling protein nanomaterials is an outstanding challenge. Here, we describe the computational design of a protein filament formed from a monomeric subunit which binds a peptide ligand. The cryoEM structure of the micron scale fibers is very close to the computational design model. The ligand acts as a tunable allosteric modulator: while not part of the fiber subunit-subunit interfaces, the assembly of the filament is dependent on ligand addition, with longer peptides having more extensive interaction surfaces with the monomer promoting more rapid growth. Seeded growth and capping experiments reveal that the filaments grow primarily from one end. Oligomers containing 12 copies of the peptide ligand nucleate fiber assembly from monomeric subunit and peptide mixtures at concentrations where assembly occurs very slowly, likely by generating critical local concentrations of monomer in the assembly competent conformation. Following filament assembly, the peptide ligand can be exchanged with free peptide in solution, and it can be readily fused to any functional protein of interest, opening the door to a wide variety of tunable engineered materials.

Mid-infrared optical coherence tomography and machine learning for inspection of 3D-printed ceramics at the micron scale

IntroductionIn this paper, recent developments in non-destructive testing of 3D-printed ceramics and monitoring of additive manufacturing of ceramics are presented.MethodsIn particular, we present the design and use of an inline mid-infrared optical coherence tomography (MIR-OCT) system to evaluate printed and micro-structured specimens in lithography-based ceramic manufacturing (LCM).ResultsThe proposed system helps with the detection of microdefects (e.g., voids, inclusions, deformations) that are already present in green ceramic components, thereby reducing the energy and costs incurred.DiscussionThe challenges during integration are discussed. Especially, the prospects for MIR-OCT imaging combined with machine learning are illustrated with regard to inline inspection during LCM of printed ceramics.

Nano-tribological behavior and structural evolution of 304 stainless-steel by molecular dynamics simulation and experiment

304 stainless-steel has excellent mechanical properties and is commonly used in ultra-precision instrumentation. Nevertheless, the research on the intricate nano tribological behavior of 304 stainless-steel during ultra-precision machining remains limited. In this work, the tribological behavior of 304 stainless-steel is investigated at different indentation depths and scratching velocities by molecular dynamics (MD) simulations and nano-scratch tests. The results show that higher indentation depths lead to more serious damage on the surface and subsurface of 304 stainless-steel. The friction force and friction coefficient also increase significantly with higher indentation depths. It is worth noting that the dislocation density is much smaller at the low-indentation depth, which is due to the large-scale dislocation annihilation at this depth. As the scratch velocity increases, the subsurface shear stress decreases, the dislocation length rises, and it is accompanied by the generation of V-shaped dislocations, which are caused by dislocation entanglement within the substrate. In addition, nano-scratch tests were performed and similar trends were obtained by comparing the results with simulations. This work provides theoretical guidance for a deeper understanding of the deformation behavior of 304 stainless-steel during nano-scratching and its engineering applications at the micron and nano-meter scales.

Study on the condensate gas phase behavior in Nano-porous media

The pore size in shale has reached the nanoscale. The phase behavior of fluids in nanopores deviates from classical theory, making conventional phase theory inapplicable to shale reservoirs. It is thus of great significance to clarify the phase behavior at the nanometer pore scale in shale. Based on the shale reservoir in the Kaybob of the Duvernay shale, Canada, 6 nm and 10 nm cubic model systems were constructed, and a microscopic physical model was prepared included pathways at 10 nm, 40 nm, 500 nm, and micrometer scale. The fluid phase behavior in nanopores was studied using molecular simulations and nanofluidic chip experiments. The results show that during the retrograde condensation process, the condensate gas in small-scale pores condenses first and is less likely to evaporate as the pressure decreases. The conclusions drawn are: (1) In nanopores, the dew point pressure of condensate gas is higher than that of the bulk phase, and the smaller the scale of nanopores, the higher the dew point pressure. (2) The volume ratio of condensate in nanopores is higher, increasing as pore size decreases. (3) The condensation rate of condensate in nanoporous media varies slowly with pressure drop; During evaporation, the condensation rate of condensate in small pores varies more slowly with pressure drop compared to the bulk phase but is faster in large pores.

Nanoporous Aramid Nanofiber Separators with High Modulus and Thermal Stability for Safe Lithium-Ion Batteries.

Developing high-safety separators is a promising strategy to prevent thermal runaway in lithium-ion batteries (LIBs), which stems from the low melting temperatures and inadequate modulus of commercial polyolefin separators. However, achieving high modulus and thermal stability, along with uniform nanopores in these separators, poses significant challenges. Herein, the study presents ultrathin nanoporous aramid nanofiber (ANF) separators with high modulus and excellent thermal stability, enhancing the safety of LIBs. These separators are produced using a microfluidic-based continuous printing strategy, where the flow thickness can be meticulously controlled at the micrometer scale. This method allows for the continuous fabrication of nanoporous ANF separators with thicknesses ranging from 1.6 ± 0.1µm to 2.7 ± 0.1µm. Thanks to the double-side solvent diffusion, the separators exhibit controllably uniform pore sizes with a narrow distribution, spanning from 40 ± 5nm to 105 ± 9nm, and a high modulus of 3.3 ± 0.5GPa. These nanoporous ANF separators effectively inhibit lithium dendrite formation, resulting in a high-capacity retention rate for the LIBs (80% after 240 cycles). Most notably, their robust structural and mechanical stability at elevated temperatures significantly enhances LIB safety under transient thermal abuse conditions, thus addressing critical safety concerns associated with LIBs.

Implementing reactivity in molecular dynamics simulations with harmonic force fields

The simulation of chemical reactions and mechanical properties including failure from atoms to the micrometer scale remains a longstanding challenge in chemistry and materials science. Bottlenecks include computational feasibility, reliability, and cost. We introduce a method for reactive molecular dynamics simulations using a clean replacement of non-reactive classical harmonic bond potentials with reactive, energy-conserving Morse potentials, called the Reactive INTERFACE Force Field (IFF-R). IFF-R is compatible with force fields for organic and inorganic compounds such as IFF, CHARMM, PCFF, OPLS-AA, and AMBER. Bond dissociation is enabled by three interpretable Morse parameters per bond type and zero energy upon disconnect. Use cases for bond breaking in molecules, failure of polymers, carbon nanostructures, proteins, composite materials, and metals are shown. The simulation of bond forming reactions is included via template-based methods. IFF-R maintains the accuracy of the corresponding non-reactive force fields and is about 30 times faster than prior reactive simulation methods.

Influence of fractions with different molecular weight distributions from high-amylose starches on their digestibility after recrystallization

Type 3 resistant starches (RS3) were prepared from debranched starch (DBS) with different average degree of polymerization (DP) generated from high-amylose pea starch (HAPS) and high-amylose maize starch (HAMS). The results showed that RS3 with DP 35 and DP 39 had the highest RS content (74.5 % and 75.0 %, respectively) after cooking, which were remarkably higher than those of RS3 prepared from mixed fractions (60.6 % and 49.0 %, respectively) and other separated fractions (34.1–63.0 %). The multi-scale structures of RS3, including short-range molecular order, crystalline structure, micro-ordered aggregate structure, microscopic structure, and particle size distribution, were influenced by the average DP. Notably, RS content was positively correlated with the proportion of DP 51–80 and negatively correlated with the proportion of DP 21–30. DBS with DP 51–80 contributed to a more organized micro-ordered aggregate structure at nanometer scale and a larger aggregate structure at micrometer scale, which improved the resistance of RS3 to amylolytic enzymes. However, DBS with DP 21–30 tended to form random coil structure that were more easily to be digested. This research offered new insights into the structure-digestibility relationship of RS3, which is meaningful for the development of RS3 with high resistance to amylolytic enzymes after cooking.

Sensing performance comparison for temperature and liquid level sensor based on uniform and step-Etched microfiber TFBG

By using the hydrofluoric acid uniform-etching and step-etching methods, a tilted fiber Bragg grating (TFBG) microfiber structure was fabricated, where the cladding diameter of the traditional TFBG was reduced to micrometer scale. The temperature sensing characteristics of the uniform-etched and step-etched microfiber TFBGs were experimentally studied and compared. The core mode of its transmission spectrum was used for sensing the temperature change; while the normalized area of cladding modes has been used for real-time monitoring the liquid level. The simultaneous measurement of temperature and liquid level has been experimentally demonstrated for the proposed microfiber TFBG. By combining the strong evanescent field of microfiber and the unique structural advantages of TFBG, the proposed microfiber TFBG has a great potential in developing the miniature optical fiber sensors.

Digital Microbe: a genome-informed data integration framework for team science on emerging model organisms

The remarkable pace of genomic data generation is rapidly transforming our understanding of life at the micron scale. Yet this data stream also creates challenges for team science. A single microbe can have multiple versions of genome architecture, functional gene annotations, and gene identifiers; additionally, the lack of mechanisms for collating and preserving advances in this knowledge raises barriers to community coalescence around shared datasets. “Digital Microbes” are frameworks for interoperable and reproducible collaborative science through open source, community-curated data packages built on a (pan)genomic foundation. Housed within an integrative software environment, Digital Microbes ensure real-time alignment of research efforts for collaborative teams and facilitate novel scientific insights as new layers of data are added. Here we describe two Digital Microbes: 1) the heterotrophic marine bacterium Ruegeria pomeroyi DSS-3 with > 100 transcriptomic datasets from lab and field studies, and 2) the pangenome of the cosmopolitan marine heterotroph Alteromonas containing 339 genomes. Examples demonstrate how an integrated framework collating public (pan)genome-informed data can generate novel and reproducible findings.

DNA Hierarchical Superstructures from Micellar Units: Stiff Hydrogels and Anisotropic Nanofibers.

Supramolecular materials have been assembled using a wide range of interactions, including the hydrophobic effect, DNA base-pairing, and hydrogen bonding. Specifically, DNA amphiphiles with a hydrophobic building block self-assemble into diverse morphologies depending on the length and composition of both blocks. Herein, we take advantage of the orthogonality of different supramolecular interactions - the hydrophobic effect, Watson-Crick-Franklin base pairing and RNA kissing loops - to create hierarchical self-assemblies with controlled morphologies on both the nanometer and the micrometer scales. Assembly through base-pairing leads to the formation of hybrid, multi-phasic hydrogels with high stiffness and self-healing properties. Assembly via hydrophobic core interactions gives anisotropic, discrete assemblies, where DNA fibers with one sequence are terminated with DNA spheres bearing different sequences. This work opens new avenues for the bottom-up construction of DNA-based materials, with promising applications in drug delivery, tissue engineering, and the creation of complex DNA structures from a minimum array of components.

Optimising 4D imaging of fast-oscillating structures using X-ray microtomography with retrospective gating

Imaging the internal architecture of fast-vibrating structures at micrometer scale and kilohertz frequencies poses great challenges for numerous applications, including the study of biological oscillators, mechanical testing of materials, and process engineering. Over the past decade, X-ray microtomography with retrospective gating has shown very promising advances in meeting these challenges. However, breakthroughs are still expected in acquisition and reconstruction procedures to keep improving the spatiotemporal resolution, and study the mechanics of fast-vibrating multiscale structures. Thereby, this works aims to improve this imaging technique by minimising streaking and motion blur artefacts through the optimisation of experimental parameters. For that purpose, we have coupled a numerical approach relying on tomography simulation with vibrating particles with known and ideal 3D geometry (micro-spheres or fibres) with experimental campaigns. These were carried out on soft composites, imaged in synchrotron X-ray beamlines while oscillating up to 400 Hz, thanks to a custom-developed vibromechanical device. This approach yields homogeneous angular sampling of projections and gives reliable predictions of image quality degradation due to motion blur. By overcoming several technical and scientific barriers limiting the feasibility and reproducibility of such investigations, we provide guidelines to enhance gated-CT 4D imaging for the analysis of heterogeneous, high-frequency oscillating materials.

Femtosecond laser controllable annealing for color centers based on ion-implanted silicon carbide substrate

As a representative of third-generation semiconductors, silicon carbide serves as a new platform for quantum nano-optics with readable paramagnetic color centers such as silicon vacancies. The potential applications include biomedical imaging, quantum sensing and micro/nano environment detection. Color centers are usually prepared based on ion-irradiated substrates, then annealed at high temperature to increase the yield. Currently, annealing furnaces have been the main method to heat the substrate and achieve annealing of the whole sample. However, further exploration is still necessary for fine processing requirements such as specialized annealing regions with certain shapes. In this work, we applied femtosecond laser to achieve controllable annealing at micron scale, based on silicon carbide substrate after ion injection. The whole process of point, line and pattern annealing was realized. The annealing area demonstrates enhanced photoluminescence, attributed to silicon vacancy color centers. Raman and photoluminescence spectra reveal that the annealing effect is primarily influenced by the number of pulses per unit area. The mechanism of femtosecond laser annealing was introduced. Finally, the controllable annealing areas with various shapes were prepared based on the comprehensive optimal parameters (100 kHz pulse repetition frequency, 105 point annealing pulses, 10 μm/s line scanning speed). This annealing strategy demonstrates excellent stability and uniformity, as well as micron scale accuracy. Additionally, the excited state lifetime of silicon vacancy was extracted and quantified. The result means that femtosecond laser annealing enhances the optical properties and quantum application potential of color centers. This work can be further extended to other semiconductors as well as patterned modification of local surface/planes at some depth, and helpful to explore the mechanism and applications of femtosecond laser annealing.

Nanoscale subsurface imaging by non-steady-state electron beam-driven scanning thermoelectric capacitance microscopy

Nanoscale subsurface characterization technologies based on the scanning electron microscope platform offer incomparable advantages of nondestructiveness and penetration depths up to the micrometer scale. However, the electron beam can serve not just as a mechanical/electrical excitation source but also as an excellent nanoscale thermal excitation source, which can facilitate the development of nanoscale subsurface imaging methods based on the Seebeck effect in semiconducting materials. In this work, a subsurface nondestructive imaging technology, scanning thermoelectric capacitance microscopy (STeCM), was developed based on the interaction between a non-steady-state electron beam and semiconducting materials, exploiting the Seebeck effect. In STeCM, a square wave-modulated hot electron beam with huge kinetic energy excites a “thermal wave” in the subsurface local region of the semiconducting sample. The heated local region, acting as a thermoelectric capacitor, undergoes cyclic charging and discharging, leading to the generation of periodic current due to non-equilibrium carrier migration. The second-order harmonic component of this current is demodulated to visualize embedded local thermal/thermoelectric inhomogeneities. Amazingly, for STeCM sample, only a smooth or polished surface is required, eliminating the need for any microfabrication, which will effectively decrease the configuration difficulty in the experiment. STeCM offers an alternative subsurface nondestructive imaging technology for more efficient, simple, and robust characterization.

An in-situ three-dimensional study of the dynamic and mechanism during spark plasma sintering of aluminum alloys

An in-situ plasma spark sintering (SPS) apparatus, coupled with laboratory X-ray microscopy, was utilized to three-dimensionally investigate the dynamic evolution process of 7055 aluminum alloy during SPS process. The influences of sintering temperatures and particle morphology on the sintering kinetics were discussed in detail. It was observed that elevating the sintering temperatures enhanced both the rate of densification and the final compactness of the alloy. Furthermore, three-dimensional quantitative analysis of pore evolution indicated that greater discrepancies in powder size between neighboring particles facilitated pore elimination during sintering by increasing available interstitial spaces. Mechanistic analysis rationalized these observations by attributing the enhanced sintering kinetics to the greater particle size disparity, which resulted in higher necking curvature and accelerated densification. The present study therefore provides a comprehensive three-dimensional in-situ quantitative analysis on the dynamic SPS process, and is expected to advance the current comprehension of sintering mechanisms at the micron scale.

A tunable transition metal dichalcogenide entangled photon-pair source

Entangled photon-pair sources are at the core of quantum applications like quantum key distribution, sensing, and imaging. Operation in space-limited and adverse environments such as in satellite-based and mobile communication requires robust entanglement sources with minimal size and weight requirements. Here, we meet this challenge by realizing a cubic micrometer scale entangled photon-pair source in a 3R-stacked transition metal dichalcogenide crystal. Its crystal symmetry enables the generation of polarization-entangled Bell states without additional components and provides tunability by simple control of the pump polarization. Remarkably, generation rate and state tuning are decoupled, leading to equal generation efficiency and no loss of entanglement. Combining transition metal dichalcogenides with monolithic cavities and integrated photonic circuitry or using quasi-phasematching opens the gate towards ultrasmall and scalable quantum devices.

Microcapsule preparation process research and current status of oilfield application

AbstractTraditional tertiary oil recovery methods are fraught with challenges such as significant reagent adsorption, voluminous injection requirements, limited sweep efficiency, and inadequate intelligent targeting. These issues lead to suboptimal displacement of residual oil, resulting in the inability to mobilize substantial crude oil resources and thus yielding low recovery rates. Microcapsules—spherical particles with micron or nanometer scale diameters—have been extensively utilized across various sectors, including food storage, targeted drug encapsulation, and fragrance containment, owing to their distinct advantages in controlled release, isolation, and targeted delivery. These applications have successfully achieved industrialization and commercialization. In recent years, numerous researchers have explored the application of microcapsule preparation processes to diverse facets of oil extraction, with the aim of further enhancing oil recovery (EOR). This article elucidates the mechanism of action of microcapsules, their preparation methods (encompassing in situ polymerization, interfacial polymerization, spray drying, solvent evaporation, phase separation, and supercritical CO2‐assisted techniques), characterization and evaluation methodologies, among other aspects. It encapsulates the current status and principal challenges associated with the application of microcapsule preparation processes in oilfield development and probes the potential and pivotal research directions for their oilfield applications.

Quantum-enhanced photoprotection in neuroprotein architectures emerges from collective light-matter interactions

BackgroundSuperradiance is the phenomenon of many identical quantum systems absorbing and/or emitting photons collectively at a higher rate than any one system can individually. This phenomenon has been studied analytically in idealized distributions of electronic two-level systems (TLSs), each with a ground and excited state, as well as numerically in realistic photosynthetic nanotubes and cytoskeletal architectures.MethodsSuperradiant effects are studied here in idealized toy model systems and realistic biological mega-networks of tryptophan (Trp) molecules, which are strongly fluorescent amino acids found in many proteins. Each Trp molecule acts as a chromophore absorbing in the ultraviolet spectrum and can be treated approximately as a TLS, with its 1La excited singlet state; thus, organized Trp networks can exhibit superradiance. Such networks are found, for example, in microtubules, actin filaments, and amyloid fibrils. Microtubules and actin filaments are spiral-cylindrical protein polymers that play significant biological roles as primary constituents of the eukaryotic cytoskeleton, while amyloid fibrils have been targeted in a variety of neurodegenerative diseases. We treat these proteinaceous Trp networks as open quantum systems, using a non-Hermitian Hamiltonian to describe interactions of the chromophore network with the electromagnetic field. We numerically diagonalize the Hamiltonian to obtain its complex eigenvalues, where the real part is the energy and the imaginary part is its associated enhancement rate. We also consider multiple realizations of increasing static disorder in either the site energies or the decay rates.ResultsWe obtained the energies and enhancement rates for realistic microtubules, actin filament bundles, and amyloid fibrils of differing lengths, and we use these values to calculate the quantum yield, which is the ratio of the number of photons emitted to the number of photons absorbed. We find that all three of these structures exhibit highly superradiant states near the low-energy portion of the spectrum, which enhances the magnitude and robustness of the quantum yield to static disorder and thermal noise.ConclusionThe high quantum yield and stable superradiant states in these biological architectures may play a photoprotective role in vivo, downconverting energetic ultraviolet photons—absorbed from those emitted by reactive free radical species—to longer, safer wavelengths and thereby mitigating biochemical stress and photophysical damage. Contrary to conventional assumptions that quantum effects cannot survive in large biosystems at high temperatures, our results suggest that macropolymeric collectives of TLSs in microtubules, actin filaments, and amyloid fibrils exhibit increasingly observable and robust effects with increasing length, up to the micron scale, due to quantum coherent interactions in the single-photon limit. Superradiant enhancement and high quantum yield exhibited in neuroprotein polymers could thus play a crucial role in information processing in the brain, the development of neurodegenerative diseases such as Alzheimer’s and related dementias, and a wide array of other pathologies characterized by anomalous protein aggregates.

Correlative morphological, elemental and chemical phase analyses at the micrometric scale of powdered materials: Application to nuclear forensics

To characterize a mixture of powders using several analytical techniques, it is necessary that successive analyses be carried out on well-identified and localized particles, so that each characterization corresponds to a given powder. In this publication, powdered nuclear materials are characterized at the morphological and elemental levels with a scanning electron microscope (SEM) equipped with an energy dispersive X-ray spectrometer (EDS) and at the chemical level with a micro-Raman spectrometer (MRS). However, to avoid a time-consuming and insufficiently accurate microparticle relocation process between SEM/EDS and MRS, micro-Raman analyses are carried out inside the SEM using a coupling device. In this way, all three pieces of information are obtained for exactly the same micrometric spot, without moving the sample or relocating the microparticles analyzed. The information can therefore be combined to characterize each component of the mixture. In this article, we describe in detail the methodology we have developed and optimized for morphological, elemental and chemical analysis of microparticles using a combined SEM/EDS and SRM. This methodology has been applied to powdered nuclear materials in two international nuclear forensics exercises. In the first exercise, named CMX-6, the combined use of the two instruments identified the presence of PuO2 microparticles and several uranium compounds (UO2, U3O8, UO2F2) in both materials. In the second exercise, called CMX-7, the methodology developed enabled us to distinguish two chemical phases of uranium, a uranyl oxy-hydroxide and a uranyl nitrate, each characterized by specific morphologies and the detection or non-detection of a minor elemental constituent (calcium).

Fumasep FAA-3-PK-130: Exploiting multinuclear solid-state NMR to shed light on undisclosed structural properties

Fumasep FAA-3-PK-130 is considered the state-of-the-art among the different commercially available Anion Exchange Membranes (AEMs). It is produced by Fumatech GmbH as a cost-effective blend of polyetheretherketone (PEEK) and poly (phenylene oxide) (PPO) characterized by high hydroxyl ions conductivity, high thermal and chemical resistance, and high dimensional stability. Nevertheless, the chemical structure of the anion exchange sites and their contents were unknown so far.In this paper, we report a detailed structural characterization of Fumasep FAA-3-PK-130 to identify the material phase composition, the nature of the conducting moieties and their interactions with the adsorbed water molecules. A complete phase segregation between PPO and PEEK was found on a micrometric scale from 1H spin-lattice relaxation times and micro-ATR analysis. Multinuclear (1H, 13C, 19F) Solid-State NMR spectra, combined with nuclear spin relaxation measurements, allowed us to identify the anion exchange moiety with benzyl-ethyl-dimethylammonium. This is present as functionalizing group of PPO monomers with a functionalization degree of about 40 %. Moreover, the mobility of water absorbed in the membrane was studied by 2H Solid-State NMR on samples hydrated with deuterated water under controlled relative humidity: at low relative moisture, two different types of environments were found for water molecules, compatible with two types of water-ion clusters, one of which contains water molecules with a restricted mobility, limited to C2 jumps, due to strong interactions with ions.