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Objectives Polymers have emerged as constituent materials for the creation of microscale neural interfaces; however, limitations regarding water permeability, delamination, and material degradation impact polymeric device robustness. Liquid crystal polymers (LCPs) have molecular order like a solid but with the fluidity of a liquid, resulting in a unique material, with properties including low water permeability, chemical inertness, and mechanical toughness. The objective of this article is to review the state-of-the-art regarding the use of LCPs in neural interface applications and discuss challenges and opportunities where this class of materials can advance the field of neural interfaces. Materials and methods This review article focuses on studies that leverage LCP materials to interface with the nervous system in vivo. A comprehensive literature search was performed using PubMed, Web of Science (Clarivate Analytics), and Google Scholar. Results There have been recent efforts to create neural interfaces that leverage the material advantages of LCPs. The literature offers examples of LCP as a basis for implantable medical devices and neural interfaces in the form of planar electrode arrays for retinal prosthetic, electrocorticography applications, and cuff-like structures for interfacing the peripheral nerve. In addition, there have been efforts to create penetrating intracortical devices capable of microstimulation and resolution of biopotentials. Recent work with a subclass of LCPs, namely liquid crystal elastomers, demonstrates that it is possible to create devices with features that deploy away from a central implantation site to interface with a volume of tissue while offering the possibility of minimizing tissue damage. Conclusion We envision the creation of novel microscale neural interfaces that leverage the physical properties of LCPs and have the capability of deploying within neural tissue for enhanced integration and performance.

Spacesuits and spacecraft must endure high velocity impacts from micrometeoroids. This work considers the impact of 100 μm diameter projectiles into composite targets at velocities from 0.5 km/s to 2 km/s. This work begins by presenting an energy-based theoretical model relating depth of penetration (DoP) and impact force to impact velocity, characteristic time, and threshold velocity and force. Next, this work compares numerical simulations of normal impact on composites to the theoretical model. Numerical simulations are conducted with LS-DYNA and the well-known composite model, MAT-162. The numerical models consider unidirectional S2-glass fiber reinforced SC-15 epoxy composite laminates. The numerical model shows good correlation with the theoretical model. The numerical model also investigates lateral impact, parallel to the fiber direction, and oblique impact at angles from 30° to 82.5°. This work decomposes oblique impact into normal and lateral components, and compares them with normal and lateral impact results. The results show good correlation of the normal component of oblique results with the theoretical model. This numerical and theoretical study focuses on DoP, velocity, and penetration resistance force as functions of time. The theoretical model and numerical simulations are used to determine new DoP parameters: characteristic time of depth of penetration and threshold impact velocity. These models are a first step in developing the capability to predict DoP for oblique, microscale, high-speed impact on composite materials.

Living systems are characterized by their spatially highly inhomogeneous nature which is susceptible to modify fundamentally the behavior of biomolecular species, including the proteins that underpin biological functionality in cells. Spatial gradients in chemical potential are known to lead to strong transport effects for colloidal particles, but their effect on molecular scale species such as proteins has remained largely unexplored. Here, we improve on existing diffusiophoresis microfluidic technique to measure protein diffusiophoresis in real space. The measurement of proteins is made possible by two ameliorations. First, a label-free microscope is used to suppress label interference. Second, improvements in numerical methods are developed to meet the particular challenges posed by small molecules. We demonstrate that individual proteins can undergo strong diffusiophoretic motion in salt gradients in a manner which is sufficient to overcome diffusion and which leads to dramatic changes in their spatial organization on the scale of a cell. Moreover, we demonstrate that this phenomenon can be used to control the motion of proteins in microfluidic devices. These results open up a path towards a physical understanding of the role of gradients in living systems in the spatial organization of macromolecules and highlight novel routes towards protein sorting applications on device.

Extracellular vesicles (EVs) are membrane vesicles secreted by cells, playing critical roles in mediating intercellular communications for various physiological and pathological processes. Most of the EV analysis is currently performed at the bulk level, obscuring the origin of the EVs and diverse characteristics of the individual extracellular vesicle. Technologies to analyze the extracellular vesicles at the single-cell and single-vesicle levels are needed to evaluate EV comprehensively and decode the heterogeneity underlying EV secretion. Microfluidic platforms that could control and manipulate fluids at the microscale provide an efficient way to achieve the aims. Various microfluidics-based technologies are emerging to realize single-cell EV secretion analysis and single EV analysis, which would be summarized in this mini-review.

Shale mechanical properties are important for shale gas production, but the magnitudes are difficult to estimate, standard size cores are hard to sample, and secondary interstice generation is inevitable. This paper proposes a method for determining shale macroscale modulus, which is determined at a hierarchy of scales from the nano-to macro-scales. Microscale measurements are upscaled to estimate the corresponding magnitudes at the macroscale. A case study is conducted with Silurian shale samples, using the hierarchy scales, gridding nanoindentation, atomic force microscopy (AFM), mineral liberation analysis (MLA), X-ray diffraction (XRD), and uniaxial compression tests. The mineral compositions are analyzed using MLA and XRD, and the shale composition is described in terms of clay minerals, organic matter, and siliceous and carbonate contents. The variation in the Young's modulus is analyzed based on the recorded indentation depth curves and modulus distributions. The nanoindentation and AFM results are upscaled to the centimeter scale through the Mori–Tanaka method. The upscaled results exhibit satisfactory fitting with the conventional uniaxial compression results, although the fitting of the upscaled AFM results is better than nanoindentation. The proposed approach can be applied to promptly and comprehensively predict the shale mechanical parameters during shale gas exploration.

In the last two decades, the micromanipulation technique has been widely utilized in industrial and biological fields. However, existing micromanipulation methods can hardly meet all the demands in both fields. In this paper, we present an all-purpose magnetically driven micromanipulation system with designed contact and non-contact modes for numerous industrial and biological applications, respectively. In the system, a micropipette containing the ferromagnetic beads driven by the magnetic field presents high-precision and high-speed motions. With another micropipette, this two-finger microhand can efficiently perform the chopstick-like grasp motion by physical contact. The vibration-based active release relying on the high-speed motion can help release the targets adhering to the end-effector. Besides, local whirling flow surrounding the micropipette induced by high-speed circular motion can trap, transport, and rotate micro-targets without contact like a hydrodynamic tweezer to operate micro bio-targets without any damages. In experiments, microbeads are grasped and released efficiently in the desired positions using the chopstick-like two-finger microhand mode, and the arrays of a hexagon and "T MECH" have been assembled. The hydrodynamic tweezer mode is adopted to trap, transport, and rotate the microbeads and further applied in the operations of the mouse egg cells. We believe the proposed magnetic micromanipulation system, as an all-purpose tool at the microscale, holds great potential in industrial and biological applications.

The study of Frequency Selective Surface (FSS) by Direct ink writing (DIW) has attracted much attention due to the convenience and effectiveness of 3D printing technology. However, the limited printing precision of DIW has heavily restricted its applications as the electromagnetic performance is highly sensitive to it, especially the precision at the microscale. Herein, the ultra-high printing precision of FSS was achieved through DIW by the uniformly dispersed graphene sheets to deeply modify the rheological behavior and the steric hindrance effect. Thus, the highly precision of the printed filament width as thin as 67 μm with a space of only 42 μm were achieved, which is difficult for conventional DIW, and no structural distortion is found after 3D printing, no matter it was 2D printed on a flat surface or the sharply skewed hook face, or even 3D printed to architectural structures. According to the highly improved precision, the electromagnetic performance matching between the designed model and the printed physical FSS device was perfectly achieved, reducing the center frequency error less than 0.3 GHz, and the transmission coefficient error less than 0.046. Our work promises an effective and easy preparation of high-quality FSS from the aid of graphene.

The effect of water contact on the propagation of microscale surface cracks is investigated in two types of glass: annealed and tempered glass. Initial flaw is artificially created on the glass surface using a Vickers indenter, and is covered with a water droplet for 20 min. Micrographs of the flaw taken before and after water contact confirms the increase in crack length from around 61 to 103 µm for thermally tempered glass. After water dipping, the maximum length to which the crack growth is approximately 57% smaller in the thermally tempered glass than in the annealed glass. Despite the severe effect of water contact on crack propagation, it is found that the fracture strength is not substantially altered by water dipping; even though the crack length is enlarged, the fracture strength of glass is similar, and in the case of tempered glass, its fracture strength is slightly changed within 7% due to the blunting of the crack tip by water or others.

Nanoscale macromolecular biological structures exhibit time-dependent mechanical behavior, yet a quantitative understanding of their creep and stress relaxation behavior remains elusive, largely due to experimental challenges in attaining sufficient spatial and temporal resolution and control of stress or strain in conditions that guarantee their molecular integrity. To address this gap, an experimental methodology was developed to conduct creep and stress relaxation experiments with individual mammalian collagen fibrils. An image-based edge detection method, implemented with high magnification optical microscopy and combined with closed-loop proportional–integral–derivative (PID) control, was implemented and calibrated to apply constant force or stretch ratio to individual collagen fibrils via a Microelectromechanical Systems (MEMS) device. This experimental methodology allowed for real-time control of uniaxial tensile stress or strain with ~25 nm displacement accuracy. The overall experimental system was tuned to apply step inputs with rise times below 0.5 s, less than 5% overshoot, and steady-state error smaller than 1%. Three collagen fibrils with diameters in the range 101–121 nm were subjected to creep and stress relaxation tests in the range 4–20% engineering strain, under partially hydrated conditions. The collagen fibrils demonstrated non-linear viscoelastic behavior that was described well by the adaptive quasi-linear viscoelastic model. The results of this study demonstrated for the first time that mammalian collagen fibrils, the building blocks of connective tissues, exhibit nonlinear viscoelastic behavior in their partially hydrated state.

The direct simulation Monte Carlo (DSMC) method was used to simulate microbackward-facing step flows in both slip and transition flow regimes. A DSMC code was developed and validated with microchannel flows. The effects of Kn number in flow characteristics were analyzed in detail. It was found that the phenomena of flow separation, recirculation, and reattachment will disappear as Kn number exceeds 0.1. A significant jump of pressure and velocity behind the step was observed in the transition flow regime. The effect of the compressibility is also discussed. The compressibility has significant effect on flow characteristics in the slip flow regime but would be negated by the rarefaction in the transition flow regime.

Molecular self-assembly is the most important strategy for the development of chiral aggregates and chiral functional materials. In this study, we rationally designed and synthesized chiral fluorescent heteroclusters that were self-assembled into microscale cubosomes with a three-dimensional (3D) bicontinuous cubic phase nanostructure. The cubosomes exhibited chirality, indicating that chirality is transferred from the molecules to the 3D nanostructure. Therefore, we confirmed the formation of a chiral bicontinuous cubic phase nanostructure for the first time. We also showed that this chirality originates from the continuous change in the saddle-splay distortion of the molecules within the curved bilayer. At the same time, transparent films of chiral composites were prepared by mixing the chiral cubosomes with an epoxy resin and then curing the mixture. Therefore, we demonstrated an effective method for preparing chiral composites.

Biopolymers, including DNA and peptides have been used as excellent self-assembling building blocks for programmable single-component or hybrid materials, due to their controlled molecular interactions. However, combining two assembling principles of DNA-based programmability and peptide-based specific molecular interactions for hybrid structures to microscale has not yet been achieved. In this study, we describe a hybrid microsystem that emerges from the co-assembly of DNA origami structure and short elastin-like polypeptide conjugated oligonucleotides, and initiates liquid-liquid phase separation to generate microdroplets upon heating above the transition temperature. Moreover, the hybrid microdroplets are capable for guest molecule trapping and perform bi-/tri-enzymatic cascades with rate enhancements as open “microreactors”. Our programmed assembled DNA-peptide microsystem represents a new combination of DNA nanotechnology and peptide science and opens potential application routes toward life-inspired biomaterials .

The thermal conductivity of the soil skeleton λs is an extremely important parameter from the point of view of the correct assessment of soil overall/effective conductivity. This work introduces the concept of “local thermal conductivity fluctuation” which characterizes the microscale variation of conductivity within the solid phase. It is proposed to link the “local fluctuation” of thermal conductivity λ with the soil texture – the information that is available at the scale of engineering applications. It was possible to relate the skeleton thermal conductivity with the grain size distribution of the soil. Finally, based on a large series of numerical simulations, the paper provides four triangle diagrams (at different organic matter contents: 0%, 2%, 4% and 6%) relating the value of λs with volume fraction of individual soil separates. This result is extremely important from the practical point of view. One can quickly evaluate λs value provided that information on the grain size distribution and organic matter content is available.

Currently, the high temperature and severe friction conditions at the tool-chip interface are the main reasons for ceramic tool wear failures. Surface texturing as a geometric extension for cutting tools is a promising way to extend their service life. In this study, a novel type of multiscale texture was developed, and its effect on the cutting performance of an Al2O3/TiC ceramic cutting tool while machining AISI H13 steel was explored in a conventional cooling environment. The cutting force, cutting temperature, and tool wear morphology were investigated at cutting velocities ranging from 80 to 249 m/min. Microgroove textured Al2O3/TiC ceramic tools were prepared for comparison. The results show that the structure of the multiscale textures maintained good integrity over the range of cutting velocities. Thus, the synergistic effect of the microscale and nanoscale textures promoted the introduction and permeation of the cutting fluid. Therefore, the multiscale textures effectively enhanced the cutting performance of the Al2O3/TiC ceramic tools.

Previous papers have demonstrated how nanoparticles in the Microscale Selective Laser Sintering process densify under conditions of isothermal heating, yielding a time calibration factor which relates the predicted sintering time to simulation time. However, it is important to quantify the uncertainty related to the time calibration factor in order to state with any degree of confidence the sintering window during which the physical process can be expected to achieve the degree of sintering predicted by the simulation. As such, the goal of this paper is to quantify the uncertainty related to the time calibration factor.

Superhydrophobic surfaces have great potential for applications in electric power equipment, photovoltaic cell panels, and other fields due to their unique self-cleaning and dry storage characteristics. However, the common process for preparing superhydrophobic surfaces faces the following problems: complex preparation process, high cost, and easily damaged hydrophobic surface structure. In this study, a self-growing monoclinic phase of BaAl2Si2O8 glass-ceramics with a microscale structure is used as a matrix, which was etched with hydrofluoric acid and then treated with 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane to obtain a kind of superhydrophobic surface with a contact angle more than 150°. The effect of the etching time on the hydrophobicity and the micromorphology of the glass-ceramic surface is analyzed. The results show that the contact angle first increases, then stabilizes, and finally decreases with increasing etching time. This etched structure has a large number of bulges and voids, and parts of the surface hydrophobic groups stay away from direct contact with other objects. Thus, it protects the internal hydrophobic group and improves the mechanical stability of the superhydrophobic surface. This study offers a simple and inexpensive idea for the mass production of ceramic-based superhydrophobic materials.

Here, the influence of grinding media with different shapes on the flotation performance of spodumene and its potential mechanism from microscale insights was investigated using a single mineral flotation experiment, X-ray diffraction (XRD) test, scanning electron microscopy combined with energy dispersive spectrometry (SEM-EDS), atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS). The flotation data indicated that under anionic/cationic (sodium oleate (NaOL)/DDA) collectors system, the rod milled spodumene has a higher floatability than ball milled ones. XRD results confirmed that rod medium makes spodumene exposed more {1 1 0} and {1 0 0} planes, while ball medium makes spodumene exposed more {0 1 0} planes. The typical anisotropic surface of spodumene makes the surface of rod milled spodumene possess more Al sites, further confirmed by SEM-EDS and XPS results. Additionally, it was found that the rod milled spodumene presents a larger value of elongation and flatness, which are parameters closely related to bubble adhesion. AFM analysis indicated that rod milled products have a rougher surface, while ball milled products have a smoother surface. Consequently, the rod medium enhanced the adsorption of NaOL/DDA on the spodumene surfaces. This work provides theoretical guidance for optimizing the separation of spodumene from the perspective of grinding.

Symmetrical multi-inlet vortex separators/reactors have been demonstrated to be beneficial for gas-particle separation and mass transfer, but their internal energy dissipation has remained unknown. This work designed a series of microscale vortex separators/reactors with single-, dual-, and quadruple inlet(s), to conduct a comparative investigation on their energy-loss characteristics and nature. The response of energy loss to inlet configuration and flow rate was experimentally determined. It is found that in 30–100 L/min flow rate, the Euler number depends insignificantly upon the Reynolds number. The introduction of the multi-inlets improves the symmetry of the flow pattern but increases the gradients of vortex velocity and static pressure. RSM-based CFD simulation can effectively reveal the effect of multiple inlets on the inside flow, static pressure, and energy-loss composition. Finally, an improved semi-empirical correlation of energy loss was developed. The results may provide a positive reference for the design, optimization, and application of vortex-based separators/reactors.

Knitting is an effective technique for producing complex three-dimensional surfaces owing to the inherent flexibility of interlooped yarns and recent advances in manufacturing providing better control of local stitch patterns. Fully yarn-level modelling of large-scale knitted membranes is not feasible. Therefore, we use a two-scale homogenisation approach and model the membrane as a Kirchhoff-Love shell on the macroscale and as Euler-Bernoulli rods on the microscale. The governing equations for both the shell and the rod are discretised with cubic B-spline basis functions. For homogenisation we consider only the in-plane response of the membrane. The solution of the nonlinear microscale problem requires a significant amount of time due to the large deformations and the enforcement of contact constraints, rendering conventional online computational homogenisation approaches infeasible. To sidestep this problem, we use a pre-trained statistical Gaussian Process Regression (GPR) model to map the macroscale deformations to macroscale stresses. During the offline learning phase, the GPR model is trained by solving the microscale problem for a sufficiently rich set of deformation states obtained by either uniform or Sobol sampling. The trained GPR model encodes the nonlinearities and anisotropies present in the microscale and serves as a material model for the membrane response of the macroscale shell. The bending response can be chosen in dependence of the mesh size to penalise the fine out-of-plane wrinkling of the membrane. After verifying and validating the different components of the proposed approach, we introduce several examples involving membranes subjected to tension and shear to demonstrate its versatility and good performance., 24 pages, 14 figures

A three-dimensional model has been developed to capture burning properties of ammonium perchlorate(AP)/hydroxyl–terminated polybutadiene(HTPB) composite propellant. Interfacial coupling between condensed domain and gas phase was conducted to obtain the surface temperature and burning rate. The condensed phase was governed by heat transfer equation, and reacting Navier-Stokes equations with pressure dependent 3-step and 12-species global kinetics were adopted. The current model was verified and validated by comparing with analytical and experimental results. Thereafter, the influences of ellipsoidal AP's orientation and aspect ratio on the burning rate were investigated. The flame structure of a typical propellant with ellipsoidal AP particle was examined, and the characteristic heights of multiple flames were determined. Besides, the flame properties of a typical propellant with spherical/ellipsoidal AP particle and different AP topologies were analyzed. Furthermore, the temperature sensitivity coefficients were calculated for composite propellant with different AP contents and sizes, matching reasonably with the experimental results.

Background: Iron tailing causes great environmental and social problems. They contaminate water, air and soil. Therefore, it is of important significance to prepare iron tailing ceramsites with microscale pores which can recycle the deposited iron tailing. Objective: The aim of the research is to obtain iron tailing ceramsites with microscale pores and good mechanical performance. Methods: The iron tailing ceramsites have been characterized via Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD). Influence of the content of iron tailing, temperature and duration time on the mechanical performance of the obtained ceramsites was performed and the optimal sintering parameter was determined. The bulk density, apparent density and cylinder compressive strength of the obtained ceramsites increased as the iron tailing content, temperature and sintering time improved. Results: Duration time and sintering temperature play important roles in the formation and size of the pores of the ceramsites. The optimal iron tailing content and sintering parameter are 70 wt.%, 1100 °C for 40 min. The iron tailing ceramsites mainly consist of orthorhombic CaAl2Si2O8, monoclinic CaSiO3, hexagonal Ca7Si2P2O16, triclinic MgSiO3, triclinic Al2SiO5, and triclinic Ca2Fe2O5 phases. Iron tailing ceramsites from 1100 °C for 40 min are composed of irregular particles with several hundreds of micrometers improving the density and strength of the ceramsites. Conclusion: Iron tailing ceramsites containing microscale pores were prepared using iron tailing and fly ash, and exhibited excellent potential for application in the field of construction.

Theoretical models for food drying commonly utilise an effective diffusivity solved through curve fitting based on experimental data. This creates models with limited predictive capabilities. Multiscale modeling is one approach which can help transition to a more physics-based model minimizing the empirical information required while improving a model's predictive capabilities. However, to enable an accurate scaling operation, multiscale models require diffusivity at a fine scale (microscale). Measuring these properties is experimentally costly and time consuming as they are often temperature and/or moisture dependent. This research conducts an inverse analysis on a multiscale homogenization food drying model to deduce the temporal diffusivity of intracellular water. A representation of the real cellular water breakdown was considered and appropriate assumptions to represent its cellular heterogeneity, in relation to time, were investigated. The work uncovered that a linear decrease in intracellular water content could be assumed and thus a function for its diffusivity was developed. The proposed function is in terms of sample temperature and intracellular water content opening the possibilities to be applied to various food materials.

Microscale-based separations are increasingly being applied in the field of metabolomics for the analysis of small-molecule metabolites. These methods have the potential to provide improved sensitivity, less solvent waste, and reduced sample-size requirements. Ion-pair free microflow-based global metabolomics methods, which we recently reported, were further compared to analytical flow ion-pairing reagent containing methods using a sample set from a urea cycle disorder (UCD) mouse model. Mouse urine and brain homogenate samples representing healthy, diseased, and disease-treated animals were analyzed by both methods. Data processing was performed using univariate and multivariate techniques followed by analyte trend analysis. The microflow methods performed comparably to the analytical flow ion-pairing methods with the ability to separate the three sample groups when analyzed by partial least-squares analysis. The number of detected metabolic features present after each data processing step was similar between the microflow-based methods and the ion-pairing methods in the negative ionization mode. The observed analyte trend and coverage of known UCD biomarkers were the same for both evaluated approaches. The 12.5-fold reduction in sample injection volume required for the microflow-based separations highlights the potential of this method to support studies with sample-size limitations.

Based on the well-known principle of selective photothermolysis, laser has been a promising way for the treatment of port wine stains (PWSs). The laser wavelengths used for PWS’s clinical treatment include but are not limited to pulsed dye laser (PDL) in 585–600 nm, long-pulse 755-nm alexandrite, and 1064-nm Nd:YAG lasers. The objective of this study was to investigate the optimal wavelength for PWS’s laser treatment. A two-scale mathematic model was constructed to simultaneously quantify macroscale laser energy attenuation in two-layered bulk skin and microscale local energy absorption on target blood vessels within Krogh unit. The effects of morphological parameters, including epidermal melanin content, epidermal thickness, dermal blood content, blood vessel depth, and diameter on laser energy deposition within target blood vessels, were investigated from the visible to near-infrared bands (500–1100 nm). The energy deposition ratio of target blood vessel to epidermal surface was proposed to determine the optimal laser wavelength for PWS with different skin morphological parameters. The bioheat transfer modeling and animal experiment are also conducted to prove our wavelength optimization. The optimal wavelengths for lightly pigmented skin with small and shallow target blood vessels are 580–610 nm in the visible band. This wavelength coincides with commercially used PDL. The optimal wavelength shifts to 940 nm as the epidermal pigmentation increases or the size and blood vessel depth increases. The optimal wavelength changes to 1005 nm as the epidermal pigmentation or the size and burying depth of target blood vessel further increases. Nine hundred forty nanometers can be selected as a general wavelength in PWS treatment to meet the need in most widely morphological structure. Lasers with wavelengths in the 580–610, 940, and 1005 nm regions are effective for treating PWS because of their high optical selectivity in blood over the epidermis.

Multiscale computational modelling is challenging due to the high computational cost of direct numerical simulation by finite elements. To address this issue, concurrent multiscale methods use the solution of cheaper macroscale surrogates as boundary conditions to microscale sliding windows. The microscale problems remain a numerically challenging operation both in terms of implementation and cost. In this work we propose to replace the local microscale solution by an Encoder-Decoder Convolutional Neural Network that will generate fine-scale stress corrections to coarse predictions around unresolved microscale features, without prior parametrisation of local microscale problems. We deploy a Bayesian approach providing credible intervals to evaluate the uncertainty of the predictions, which is then used to investigate the merits of a selective learning framework. We will demonstrate the capability of the approach to predict equivalent stress fields in porous structures using linearised and finite strain elasticity theories., Comment: 50 pages, 42 figures; corrected typos; clarifications

Achieving efficient magnetoelectric coupling of core-shell and particulate multiferroic composites has been a challenging hurdle; however, research has shown unwavering interest to overcome this barrier in pursuit of their implementation into promising potential applications. Herein, a fully coupled computational model of core-shell and particulate composites is developed and verified to investigate the magnetoelectric interactions of the particle and matrix on the microscale. The effects of particle geometry, settling, and agglomeration were exhaustively studied by investigating seven different shapes and a wide range of vertical and lateral particle spacing. Overall, it was found that utilizing particle geometries and positioning that closely resemble a laminate configuration, such as a prolate ellipsoid and horizontal particle alignment, enhances the magnetoelectric coupling of the composite structure. The results coincided with the experimental results concerning settling and agglomeration.

Purpose The purpose of this paper is to investigate the effect of a vibratory bed, as an assistant agent, on the improvement of the drag finishing process. The dynamics and kinematic of the process were surveyed in microscale for different frequencies and amplitudes and the results were compared to the basic process. Design/methodology/approach The discrete element tool was used to find out the effect of the vibratory bed on the drag finishing process. To this end, the Hertz-Mindlin model was used to investigate the contact of abrasive particles and workpiece. At the first stage, the numerical model was validated with the experimental results, and then the effect of different parameters on the finishing process was evaluated and compared with the basic case. Findings The chosen numerical model was in good agreement with the results measured in the previous literature. Moreover, the results show that not only vibrated bed enhances the contacts of abrasive particles to the workpiece, but it also increases the uniformity of the finished surface. Originality/value In comparison to the experiments, the discrete element technique consumes lower cost and time to estimate the optimum conditions of the finishing process, as well as it provides a good understanding of this phenomenon on the micro-scale.

Numerous studies have focused on designing micro/nanostructured surfaces to improve wicking capability for rapid liquid transport in many industrial applications. Although hierarchical surfaces have been demonstrated to enhance wicking capability, the underlying mechanism of liquid transport remains elusive. Here, we report the preferential capillary pumping on hollow hierarchical surfaces with internal nanostructures, which are different from the conventional solid hierarchical surfaces with external nanostructures. Specifically, capillary pumping preferentially occurs in the nanowire bundles instead of the interconnected V-groove on hollow hierarchical surfaces, observed by confocal laser scanning fluorescence microscopy. Theoretical analysis shows that capillary pumping capability is mainly dependent on the nanowire diameter and results in 15.5 times higher capillary climbing velocity in the nanowire bundles than that in the microscale V-groove. Driven by the Laplace pressure difference between nanowire bundles and V-grooves, the preferential capillary pumping is increased with the reduction of the nanowire diameter. Capillary pumping of the nanowire bundles provides a preferential path for rapid liquid flow, leading to 2 times higher wicking capability of the hollow hierarchical surface comparing with the conventional hierarchical surface. The unique mechanism of preferential capillary pumping revealed in this work paves the way for wicking enhancement and provides an insight into the design of wicking surfaces for high-performance capillary evaporation in a broad range of applications.

The influence of chloride ion concentration in the pitting behavior of 309L cladding used in nuclear power plants has been investigated in-situ by potentiodynamic polarization and morphology observation using microscale electrodes and ex-situ 2D and 3D geometrical characterizations. The results indicate that the concentration of chloride ion affects not only the pitting potential but also the geometry of the pit. The effects of lowering the chloride ions concentration are to enhance the pit growth in depth rather than width. An extremely low chloride ion concentration (0.001 mol/L) cannot give rise to “normal” pitting corrosion but to a transpassivation-induced pit. The related mechanisms are also discussed.

Fog collection plays an important role in alleviating the global water shortage. Despite great progress in creating bionic surfaces to collect fog, water droplets still could adhere to the microscale hydrophilic region and reach the thermodynamic stable state before falling, which delays the transport of water and hinders the continuous fog collection. Inspired by lotus leaves and cactuses, we designed a Janus membrane that functions to both collect fog from the air and transport it to a certain region. The Janus membrane with opposite wettability contains conical microcolumns with a wettability gradient and hydrophilic copper mesh surface. The apexes of conical microcolumns are superhydrophobic and the rest are hydrophobic. The fog droplets were deposited, coalesced, and directionally transported to the bottom of the conical microcolumns. Then, the droplets unidirectionally passed through the membrane and flowed into the water film on the surface of the copper mesh. The asymmetric structural and wettability merits endow the Janus membrane with an improved fog collection of ∼7.05 g/cm2/h. The study is valuable for designing and developing fluid control equipment in fog collection, liquid manipulation, and microfluidics.

Electronics are becoming smaller and more versatile, and the size of solder joints has decreased to tens of microns, inducing obvious inhomogeneity among the phases in the solder matrix microstructure. In this study, the influence of phase inhomogeneity on the mechanical behavior of microscale Cu/Sn–58Bi/Cu solder joints was studied. Sn and Bi single-phase solid solution samples with the same composition as the Sn and Bi phases in the Sn58Bi microstructure were prepared, and their mechanical performances, elastic constants, and power-law constitutive models were measured, calculated, and identified. Based on the obtained mechanical performances, elastic constants, and power-law constitutive models, a three-dimensional finite element model of line-type Cu/Sn58Bi/Cu microscale solder joints, including their microstructure, was established. The results demonstrate that phase inhomogeneity increases the maximum value of von Mises stress, leading to stress concentration. When the Sn58Bi solder matrix transfers from the elastic deformation stage to the plastic deformation stage, the high σeq zone of the matrix gradually shifts from the Sn phase to the Bi phase. In addition, a study of the anisotropy reveals that the elastic anisotropic mechanical properties of Sn58Bi solder matrix are mainly affected by the anisotropic effect of Sn. The stress concentration is the lowest when the crystal orientation is π/2.

There is a limited understanding of the microscale interactions between fluid–oil–solid interfaces, which could be a stumbling block to the development of relevant technologies and industries. With...

Due to the mismatch of thermal expansion coefficients and effective moduli between fibers and matrix materials, local stress concentrations arise in composites during the curing process from the high preparation temperature to room temperature. To evaluate the effect of thermal residual stresses on local stress distributions in composites, a high-precision microscale model is established in this paper. The numerical results obtained indicate that the thermal residual stresses cannot give rise to plastic strains in the matrix.

Additive manufacturing techniques have revolutionized the field of fabricating micro-supercapacitors (MSCs) with a high degree of pattern and geometry flexibility. However, traditional additive manufacturing processes are based on the functionality of microstructural modulation, which is essential for device performance. Herein, Ti3C2Tx MXene was chosen to report a convenient aerosol jet printing (AJP) process for the in situ curling and alignment of MXene nanosheets. The aerosol droplet provides a microscale regime for curling MXene monolayers while their alignment is performed by the as-generated directional stress derived from the quasi-conical fiber array (CFA)-guided parallel droplet flow. Interdigital microelectrodes were further developed with the curled MXene and a satisfying areal capacitance performance has been demonstrated. Importantly, the AJP technique holds promise for revolutionizing additive manufacturing techniques for fabricating future smart microelectronics and devices not only in the microscale but also in the nanoscale.

In order to develop optimum microneedle designs, researchers must first develop robust, repeatable and adaptable test methods which are representative of in vivo conditions. However, there is a lack of experimental tools which can accurately comparatively interrogate functional microneedle penetration of tissue. In this study, we seek to develop a state of the art finite element model of microneedle insertion into and penetration of human skin. The developed model employs a 3D hyperelastic, anisotropic pre-stressed multi-layered material which more accurately reflects in vivo skin conditions, while the microneedle is modeled as an array, which can capture the influence of adjacent microneedles on the overall response. Using the developed finite element model, we highlight the importance of accurate computational modeling which can decipher the mechanics of microneedle insertion, including the influence of its position within an array and how it correlates well with experimental observations. In particular, we have concluded that, for our model microneedle array, increasing skin pretension from 0 to 10% strain reduces the penetration force by 13%, ultimate local deformation about the microneedle by 22% and the ultimate penetration efficiency by 15%. We have also concluded that the presence of a base plate limits the penetration efficiency by up to 24%, while the penetration efficiency across a 5 × 1 microneedle array may vary by 27%. This model elucidates, for the first time, the combined effects of skin tension and needle geometry on accurately predicting microneedle penetration efficiency. Statement of Significance Microneedles arrays (MNAs) are medical devices with microscale protrusions, typically designed to penetrate the outermost layer of the skin, that upon optimisation, could lead to disruptive minimally-invasive disease management. However, the mechanics of MNA insertion are complex, due in part to a ‘bed of nails’ effect, and difficult to elucidate experimentally. Therefore, comparisons between designs, functional assessment of production batches and ultimately the likelihood of clinical translation are challenging to predict. Here, we have develop the most sophisticated in silico model of MNA insertion into pre-tensioned human skin to predict the extent of MNA penetration and therefore the likelihood of successful therapeutic delivery. Researchers can customise this model to predict the penetration efficiency of any MNA design.

Nature-inspired gradients can be implemented in metallic materials to achieve a synergy of strength and ductility. However, due to the small (often microscale) size of the gradient structured samples, their fracture properties have remained relatively unexplored. By fabricating centimeter-sized gradient-structured pure nickel samples using direct-current electroplating technique, we demonstrate that a dual-gradient architecture in pure nickel, comprising grain-size transitions from coarse grains to nano grains and then back to coarse grains (CG→NG→CG), achieves an optimized combination of strength-ductility synergy and exceptional fracture resistance – a crack-initiation toughness exceeding 300 MPa m½ – while minimizing the problem of final unstable catastrophic failure. Significantly, this dual-gradient CG→NG→CG structure can effectively arrest any brittle fracture in the nano grains by inducing a stable rising R-curve with an enhanced crack-growth toughness exceeding 350 MPa m½. We believe that this dual-gradient CG→NG→CG structure provides a promising prototype for designing multi-layer graded structures with exceptional combinations of mechanical properties which can be readily tuned to meet the advanced requirements of safety-critical applications.

An easy-to-implement method by which to fabricate superhydrophobic surfaces inspired taro leaf was successfully applied on 316L stainless steel via combining nanosecond laser (NL) processing and spin-coating techniques. The laser-textured surface composed of microscale frameworks and central bumps was fabricated by NL processing based on properly designed biomimetic patterns, and a layer of nanoscale carbon black/polydimethylsiloxane (CB/PDMS) particles was covered on it by spin-coating. The effect of pattern parameters (i.e., the inscribed circle radius of framework and the radius of central bump) on wettability of biomimetic surface was investigated. All as-prepared biomimetic surfaces with micro-nano hierarchical structures showed excellent superhydrophobicity with the water contact angle of ∼155° and contact angle hysteresis of ∼2°. By comparing the untreated surface, the wetting behavior and evaporation mode of the biomimetic surface occurred an obvious transformation. Meanwhile, experiments indicated that the biomimetic surface not only had liquid-repelling and self-cleaning functions, but also maintained remarkable mechanical robustness and superhydrophobic durability. The method is efficient for fabricating biomimetic superhydrophobic surfaces applied to liquid-repelling, evaporation-transforming and self-cleaning fields.

For the reliability of cryoelectronics, the tensile performance and fracture behavior of microscale Cu/Sn3.0Ag0.5Cu/Cu joints with shrinking size were investigated at decreasing temperature ranging from 25 °C to −120 °C. The experimental results showed that the tensile behavior of solder joints was greatly influenced by temperature and joint size. The tensile strength of the solder joint increased with decreasing temperature. At a same temperature, the joint tensile strength increased with decreasing thickness-to-diameter ratio (R = t/d, 1, 1/2 and 1/4). In addition, at a same R, the joint with a smaller diameter had a higher tensile strength. In general, the tensile strength showed an inversely proportional function of solder volume. Moreover, as temperature decreased, the fracture position changed from the solder matrix to the interface between solder and intermetallic compound layer, showing a ductile-to-brittle transition. The ductile-to-brittle transition temperature increased with decreasing R in the solder joints with a same diameter, and it decreased with decreasing joint diameter in the solder joints with a same R.

Femtosecond laser machining offers a fast, low damage route to fabricating features on the order of a few micrometers to millimeters. Within this broad application space, mechanical testing samples on this scale provides a combination of region selectivity and a bulk-like response. Use of such mechanical test specimens, however, is relatively unexplored compared to microscale and macroscale testing. The present study showcases the benefit of combining efficient specimen fabrication and testing on the mesoscale for extracting a more comprehensive picture of material mechanical properties. Moreover, a material with a complex and heterogeneous microstructure, additively manufactured grade 91, has also been studied to highlight the considerations needed and limitations of testing on this scale.

The objective of this paper is to present the modeling approach for homogenizing the 3D-printed composite parts for the accurate prediction of effective mechanical properties. The Mori–Tanaka (MT) approach associated with two-step homogenization is applied to partially oriented short carbon fiber (SCF)-reinforced polycarbonate (SCF/PC)-based composites and compared with the experimental results. Detailed microstructural analysis was performed to investigate the variation in fiber length and bead dimensions that occurred due to change in fiber percentage (3%, 5%, 7.5%, and 10% by vol.). A two-step homogenization framework was performed in this research. Change in fiber length was considered in the first-step homogenization and change in bead dimensions was considered in the second step of homogenization approach to find the microscale and mesoscale constitutive properties of SCF/PC 3D-printed composite samples using the MT method respectively. Results of this study revealed that the stiffness of the composite samples increases with the increase in fiber percentage. As we increase the SCF, significant variations were observed in the fiber length and bead dimensions which also significantly affect the mechanical properties of 3D-printed composite parts. Results obtained after considering the fiber length and bead dimensions in mathematical calculation helps in reducing the error gap between the homogenized numerical and experimental results. It was also concluded that the prediction of Young’s modulus using higher fiber percentage has relatively low errors. Eventually, the properties attained from the respective approach help to find out the macro fields (average stress and average strain) in the 3D-printed composite samples.

This review article presents an overview of the evolution of the field of insulator-based dielectrophoresis (iDEP); in particular, it focuses on insulator-based electrokinetic (iEK) systems stimulated with direct current and low-frequency(

Transdermal and intradermal drug delivery utilizing microneedles is an emerging front in painless therapeutics. Drug delivery using hollow microneedles is the most preferred method for delivering generic transdermal drugs in the clinical setup. The needle tip must be extremely short as the drug is administered to sub-millimeter depths. Also, they need to be sharp enough to pierce through the skin with minimal skin flexing. There are multiple challenges in engineering a tip profile that is short and sharp at the same time. Stainless steel (SS) hypodermic needles with the lancet tip profile are ubiquitous in subcutaneous and intramuscular injections. They have long bevel lengths that make them inappropriate as microneedles. Thus, designing a unique tip profile and developing the manufacturing technology for microneedle applications are necessary. This article presents the design and optimization of microneedle tip profiles through analytical models. Further, manufacturing strategies for reliably obtaining designed profiles are discussed. The article concludes with experimental validation of improved piercing performance of the optimized tip profile compared to other tip profiles. The article discusses about tip geometries of stainless steel needles for microneedle applications, where depth of delivery is less than 1 mm. Through series of analyses, the optimum needle tip geometry evolved from single plane bevel (SPB) to hex plane bevel (HPB) progressively improving piercing performance.

Dislocations have been identified to modify both the functional and mechanical properties of some ceramic materials. Succinct control of dislocation-based plasticity in ceramics will also demand knowledge about dislocation interaction with point defects. Here, we propose an experimental approach to modulate the dislocation-based plasticity in single-crystal SrTiO3 based on the concept of defect chemistry engineering, for example, by increasing the oxygen vacancy concentration via reduction treatment. With nanoindentation and bulk compression tests, we find that the dislocation-governed plasticity is significantly modified at the nano-/microscale, compared to the bulk scale. The increase in oxygen vacancy concentration after reduction treatment was assessed by impedance spectroscopy and is found to favor dislocation nucleation but impede dislocation motion as rationalized by the nanoindentation pop-in and nanoindentation creep tests.