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Background: Thromboembolism, which leads to pulmonary embolism and ischemic stroke, remains one of the main causes of death. Ultrasound‐assisted thrombolysis (UAT) is an effective thrombolytic method. However, further studies are required to elucidate the mechanism of ultrasound on arterial and venous thrombi. Methods: We employed the blood‐on‐a‐chip technology to simulate thrombus formation in coronary stenosis and deep vein valves. Subsequently, UAT was conducted on the chip to assess the impact of ultrasound on thrombolysis under varying flow conditions. Real‐time fluorescence was used to assess thrombolysis and drug penetration. Finally, scanning electron microscopy and immunofluorescence were used to determine the effect of ultrasound on fibrinolysis. Results: The study revealed that UAT enhanced the thrombolytic rate by 40% in the coronary stenosis chip and by 10% in the deep venous valves chip. This enhancement is attributed to the disruption of crosslinked fibrin fibers by ultrasound, leading to increased urokinase diffusion within the thrombus and accumulation of plasminogen on the fibrinogen α chain. Moreover, the acceleration of the dissolution rate of thrombi in the venous valve chip by ultrasound was not as significant as that in the coronary stenosis chip. Conclusion: These findings highlight the differential impact of ultrasound on thrombolysis under various flow conditions and emphasize the valuable role of the blood‐on‐a‐chip technology in exploring thrombolysis mechanisms. [ABSTRACT FROM AUTHOR]

Five different solutions containing microparticles in different sizes were tested in a vibration cavitation erosion experiment. After the experiment, the number of erosion pits on sample surfaces, free radicals HO· in solutions, and mass loss all show that the cavitation erosion strength is strongly related to the particle size, and 500 nm particles cause more severe cavitation erosion than other smaller or larger particles do. A model is presented to explain such result considering both nucleation and bubble-particle collision effects. Particle of a proper size will increase the number of heterogeneous nucleation and at the same time reduce the number of bubble-particle combinations, which results in more free bubbles in the solution to generate stronger cavitation erosion. [ABSTRACT FROM AUTHOR]

• Unified backstress and stress sensitivity models covering creep and viscoplasticity. • Microstructure-based constitutive model to encompass diverse deformation states. • Tensile, creep and stress-relaxation are concurrently and accurately predicted. • The model greatly improves the prediction accuracy for hybrid forming of Ti alloy. A unified model to characterize the mechanism transitions in a wide range of strain rates at elevated temperatures of titanium alloys has been developed and validated in this study. Models of microstructure-based backstress and strain rate dependent stress sensitivity covering both creep and viscoplasticity domains have been proposed, so as to predict different deformation behaviors concurrently for hot forming. Systematical experiments, including hot tensile, creep, stress-relaxation, and corresponding loading-unloading tests have been designed and performed, to get the different deformation behaviors, as well as the evolution of backstresses of titanium alloys at elevated temperatures. Microstructural observations, such as electron backscatter diffraction (EBSD), have also been performed to assist the mechanisms characterization. Based on the microstructural and macro properties results, the developed unified model has been calibrated and further implemented for typical cases of hot stamping - stress-relaxation forming (HS-SRF). The developed model achieved an excellent accuracy for all the tensile, creep, and stress-relaxation behaviors concurrently, with an error of only about 4.9 %, and a comparative 71.8 % ∼ 90.8 % reduction in springback prediction error has been reported for hot forming of typical thin-walled titanium alloy components when compared with the conventional modelling strategy where a single deformation mechanism is considered. The potential of the proposed model for process design and optimizations has also been discussed. [Display omitted] [ABSTRACT FROM AUTHOR]

A diffusion-controlled method ispresented to study the growthof bubbles on a solid surface. The bubbles are nucleated spontaneouslyon a hydrophobic smooth surface in response to a sudden pressure reductionand then grow with an expanding contact line. The evolution of thebubbles in the early stage is found to grow with a constant bubbleradius and a decreasing contact angle, while the bubbles continuetheir growth with a constant contact angle and an increasing bubbleradius after the contact angle reaches its equilibrium value. A totalvariation of about 60° of the contact angle is observed duringthe growth of the bubbles with the size scale of 10–100 μmin radius. The growing process is described by the diffusion theorywith the validation of the growth constant. [ABSTRACT FROM AUTHOR]

Abstract: Ion implantation was adopted to change the surface potentials of samples made of aluminum bronze. The interactions between the SiO2 particles and the sample surfaces in water were changed from attractive to repulsive. According to the surface element integration method, this interaction was simulated and the electrostatic double layer force was considered to be the dominated factor. This long range repulsive interaction was proved to have effect on preventing micro particles approaching the alloy surface by the fluorescent particles adhesion experiment, and the technology of ion implantation may have potential applications in adhesion resistance and abrasion reduction for alloys running in water. [Copyright &y& Elsevier]

Abstract: Special rings with iridescent color were found around erosion pits on mild carbon steel surface in rotate disk cavitation erosion experiments. The EDS and XPS examinations proved that the ring was an oxidation film mainly composed of Fe2O3. The mean diameter of iridescent rings was 200–300μm, and the thickness was 200–500nm. The rings have four main kinds of the shapes, named as O-shaped, U-shaped, pies and comet rings. Their special shapes and chemical compositions indicate that the iridescent rings are products of a kind of local oxidizations related to the collapsing bubbles above them. Based on numerical and experimental results, it is explained that the hot gas in a collapsing bubble is possible to contact the metal surface to cause the high temperature oxidization, and the shape of the bubble at its final stage of collapsing is responsible for the special shape of the ring. [ABSTRACT FROM AUTHOR]

Abstract: A detail experiment investigation on hydrophobicity of lotus leaf had been given, including contact angle, entrapped gas, micrometer and nanometer surface topographies. Four kinds of lotus leaf surfaces were involved: fresh front (FF), dried front (DF), fresh back (FB) and dried back (DB) surfaces. The basic mechanisms of the liquid spreading on a rough surface and the entrapped gas under a drop had been discussed. Based on the mechanisms and experiment, hydrophobicity of the four lotus leaf surfaces was analyzed. The investigation results showed that the hydrophobicity of the front surfaces was dominated by the entrapped gas under the drop and the absolute stable position of the contact line while the back surfaces by metastable positions of the contact line, resulting in the ultrahydrophobicity on the front surfaces and large contact angle hysteresis on the back surfaces. The effects of dual-size surface structures on the hydrophobicity were discussed in detail. Because the nano-pillars were firmly close together, there was no entrapped gas in the nano-structure on the front surfaces. The structure of micro-pillars was a main cause for the ultrahydrophobicity of the front surfaces. However, on the FB surface, the structure of nano-pillars was a main cause to induce entrapped gas. [Copyright &y& Elsevier]

The characteristics of erosion pits on a carbon steel surface were investigated at the incipient stage of cavitation erosion. After a 5-minute experiment performed in an ultrasonic vibration system, needle-like erosion pits appeared on the polished steel surface, and a specially affected zone was formed around the pit. The shape of the pit and the plastic deformation of the affected zone indicate that the mechanical impaction on the surface is the main reason for the cavitation damage. On the other hand, the iridescent color, the decreased surface hardness and the precipitated carbides on the affected zone prove that the affected zone has experienced a tempering process with the temperature higher than 300°C. The lack of oxygen in the affected zone also proves that it is not a chemical oxygen result. A special phenomenon that a carbon ring forms in the affected zone is explained as a result of the toroidal bubbles' heating effect at the final stage of the bubble collapse. [ABSTRACT FROM AUTHOR]

Abstract??Polished, grinded, and milled samples made of 40Cr stainless steel were prepared for the cavitation erosion experiment. A typical phenomenon of ?pits chain?, which consisted of two contact pits and a smaller pit on the ridge between them, was found on the sample surfaces after 15-minute experiment. Numerical simulation indicated that the pressure fluctuation caused by the sequentially formed pits on the solid surface was the main reason for the formation of the ?pits chain?. It proves that the early-formed pits affect the formation of the subsequent erosion pits, and the whole cavitation erosion process is not a probability event. Based on the numerical analyses, the development of erosion is divided into four stages, which describe how a pit develops vertically and horizontally under the effect of the pressure perturbation. The development was validated by the characteristics of the damaged surface observed at different experimental time. [ABSTRACT FROM AUTHOR]

Abstract: A lubricant in a head-disk interface is considered as a non-Newtonian fluid. Properties of non-Newtonian lubricants are specified by three nonlinear functions and a modified Reynolds equation is derived for the varied film thickness in the interface. The shear dependent viscosity is the principal factor and it is expressed by a first order transfer function. Its amplitude frequency response describes the process of the viscosity variation and indicates that the shear dependent viscosity is affected not only by the lubricant material parameters, but also by the shear frequency. Based on the modified Reynolds equation, the numerical result of lubrication is given. The load capacity is not always higher or always lower than that of the Newtonian fluid. The effect of the first normal stress difference is enlarged with the slider flying height varies. [Copyright &y& Elsevier]

Discusses the use of the system identification method to identify the micro helicopter's yaw dynamics. Modification of the conventional system identification method to strengthen the information of the dynamics and reduce the effect of the noise when processing the experiment data; Calculation of the factors of the weighted criterion by training a perception to allocate the factors automatically; Suggestion that the modified system identification method would be useful in identifying dynamic systems which use the multiexperiment data.

Hydrophobic biodegradable ethyl cellulose (EC) nanoparticles are commonly used to stabilize the gas/liquid interfaces. To produce EC foams, ultrasonication with a driving frequency of 21.45 kHz is utilized. EC suspension reduced the cavitation noise, and the immersing depth of the vibrating horn influenced the foamability of the EC particles. When the horn is near the air/liquid interface, dense and homogeneous EC foams will be obtained, but when the horn is near the bottom wall, sparse and polydisperse EC foams are obtained. This is attributed to the fact that more bubbles are stabilized by the EC nanoparticles in the ultrasonic field when the horn is near the air/liquid interface; therefore, the collapse of the bubbles is suppressed, and the sound pressure level is lowered on the broadband. [ABSTRACT FROM AUTHOR]

Tetrahedrons are basic building blocks in natural and artificial materials, while the terahertz response of micro tetrahedrons has been little explored. Here we fabricate subwavelength ceramic tetrahedrons for use in the terahertz frequency range, and find that the three-dimensional geometry significantly affects their terahertz properties. The transmission spectra are independent of the orientation of the tetrahedrons, while the first magnetic resonance disappears in the reflection spectra when an upright tetrahedron is flipped upside down on the metallic substrate, which changes it from a perfect absorber to a perfect reflector. This is attributed to the destructive interference between two magnetic dipoles induced respectively by the incident and the reflected wave. The study brings new insights in the materials design with 3D building blocks to realize more interesting and exotic terahertz properties. [ABSTRACT FROM AUTHOR]

Geometric model fitting has been widely applied in the electronic industry. However, it remains as a challenging task when handling the data corrupted by a large number of false matches (i.e., severe outliers) between two-view images. In this article, we propose a novel motion consistency guided fitting method (MCF) to robustly and efficiently estimate the parameters of model instances in data involving severe outliers. Specifically, from input data, we first generate a series of neighborhood sets, in each of which gross outliers that are inconsistent in motions can be effectively filtered, according to motion consistency among true matches (i.e., inliers). Then, we propose an effective sampling algorithm to sample minimal subsets from the generated neighborhood sets. In this way, the model hypotheses computed from the sampled minimal subsets can cover all model instances with a high probability. Furthermore, by taking advantages of the generated hypotheses and neighborhood sets, we propose a novel model selection algorithm to estimate the number and the parameters of model instances. For fitting evaluation, we also build a new dataset, in which the images are collected from a fundus camera. Experiments on a variety of electronic industrial applications show that the proposed MCF achieves higher fitting accuracy at a much lower computational cost than several state-of-the-art fitting methods. [ABSTRACT FROM AUTHOR]

A systematic experimental and numerical study of the cooling rate effects on the post-formed strength and microstructure evolutions of a dual phase Ti-6Al-4V alloy under hot forming conditions was performed in this study. A series of cooling treatment tests were designed to achieve typical cooling scenarios in current hot forming processes, i.e. air cooling, water quenching and die quenching. The post-treated mechanical properties and phase volume fractions were characterized and quantified. The results show that higher temperatures and higher cooling rate would facilitate the β phase transformation and martensite transformation of α ′ phases, leading to the higher yield strength in the formed part. Based on the macro- and micro- properties relations and observed data, a unified model for the hot forming and cooling of Ti-6Al-4V was proposed and calibrated, enabling the accurate prediction of both the macro-strength and microstructures under different cooling conditions of the material. The proposed model was further implemented into FE simulation for practical forming process simulations. A typical hot gas forming process of a rectangular cross-sectioned titanium alloy hollow tubular part was investigated. Experiments of hot gas forming with different cooling conditions, i.e. forming temperatures and cooling rates, were carried out and used to validate the established material model and simulation model. Good prediction accuracy was obtained under all the tested conditions, with the maximum prediction errors of 5.55 % for macro-strength and of 9.79 % for average grain size. The results and the model developed in this paper provides an effective way to facilitate the process designs and optimization for hot forming titanium alloy parts in various applications. • Cooling rate effects on strength of hot formed Ti-6Al-4V are experimentally and numerically investigated. • Cooling induced strength changes is due to phase transformation and grain evolutions. • A unified model is developed to accurately predict cooling effects on microstructures and strengths. • The model in micro and macro properties prediction is validated by hot gas forming of typical components. [ABSTRACT FROM AUTHOR]

When a water drop approaches a solid surface in an ambient oil environment, a thin oil film will be formed between the drop and the solid surface. The lubrication film presents more complex behaviors when the external electrical field varies discretely, and in this work, concentric ripples are found in the thin film under a series of voltage steps, which is obviously different from the film profile when the applied voltage is continuously increased. According to the time evolution of the thin film, each voltage step adds a new concentric ripple outside the existing lubrication film. The radial wavelength and the maximum height of each ripple are revealed to have a linear relationship with the amplitude of the corresponding voltage step. The ripples finally break into microscopic oil droplets, and the size and the number of the droplets can be predicted with the diameter and the radial wavelength of each ripple. [ABSTRACT FROM AUTHOR]

Yttrium-stabilized zirconia(3YSZ) microspheres with different size ranges were prepared by sol-gel method, followed by electroless Ni plating on their surfaces. The as-prepared core-shell structure 3YSZ/Ni microspheres were then spark plasma sintered (SPS) into 3YSZ/Ni composites, in which a uniform distribution of ceramic and metal phases was achieved. The underlying correlations among microsphere size, Ni concentration, microstructure, and resultant mechanical properties were experimentally analyzed. Results show that: continuous and smaller microsphere sizes can obtain relatively high-density samples with good mechanical properties, which can be proved by the Minimum Solid Area (MSA) model. 3YSZ sample prepared with the optimized microsphere size range of 0–50 μm exhibits the highest relative density and fracture toughness of 98.8% and 5.51 ± 0.33 MPa·m1/2, respectively. Furthermore, the core-shell structure 3YSZ/Ni microspheres with varying Ni contents exhibited a uniform composite of flakes and particles Ni metal after sintering, among which 3YSZ/10 wt%Ni composites have achieved better mechanical properties, with density, hardness and fracture toughness of 96.9%, 8.61 ± 0.35 GPa, 7.92 ± 0.71 MPa·m1/2, respectively. Firstly, the uniformly dispersed Ni metal flakes or particles provide multiple toughening effects, including crack bridging, pull-out, interfacial debonding, crack deflection, etc. Secondly, due to residual stress, cracks tend to deflect near Ni metal, extending the crack path. Thirdly, the 3YSZ matrix's transition from an intergranular to a transgranular fracture also increases fracture energy consumption. Compared to the pure 3YSZ sample with a wide microsphere size range of 0–100 μm, the fracture toughness of 3YSZ/10 wt%Ni composites with a microsphere size of 0–50 μm is increased by 73.9%. [ABSTRACT FROM AUTHOR]

When oil drops in a continuous water phase move from the hydrophilic to the hydrophobic section of a microchannel, they can be controlled to either adhere or not adhere on the channel by changing the capillary number. Using experiments and a model for the thin film flow, we show that the critical capillary number for adhesion is approximately Ca ∼ D3/4/d3/2, where D and d is the length of the droplet and the inner dimension of the microchannel, respectively. As one application of these ideas, droplet adhesion is demonstrated as a promising technology for recycling of emulsions in droplet microfluidics. [ABSTRACT FROM AUTHOR]

Thrombosis is the leading cause of death, while the effect of the shear flow on the formation of thrombus in vascular constructions has not been thoroughly understood, and one of the challenges is to observe the origination of thrombus with a controlled flow field. In this work, we use blood-on-a-chip technology to mimic the flow conditions in coronary artery stenosis, neonatal aortic arch, and deep venous valve. The flow field is measured by the microparticle image velocimeter (μPIV). In the experiment, we find that the thrombus often originates at the constructions of stenosis, bifurcation, and the entrance of valve, where the flow stream lines change suddenly, and the maximum wall shear rate gradient appears. Using the blood-on-a-chip technology, the effect of the wall shear rate gradients on the formation of the thrombus has been illustrated, and the blood-on-a-chip is demonstrated to be a perspective tool for further studies on the flow-induced formation of thrombosis. [ABSTRACT FROM AUTHOR]

The left ventricular assist device (LVAD) is often used in the treatment of heart failure. However, 4% to 9% implanted LVAD will have thrombosis problem in one year, which is fatal to the patient's life. In this work, an interventional sonothrombolysis (IST) method is developed to realize the thrombolysis on LVAD. A pair of ultrasound transducer rings is installed on the shell of LVAD, and drug‐loaded microbubbles are injected into the LVAD through the interventional method. The microbubbles are adhere on the thrombus with the coated thrombus‐targeted drugs, and the thrombolytic drugs carried by the bubbles are brought into the thrombus by the cavitation of bubbles under the ultrasound. In a proof‐of‐concept experiment in a live sheep model, the thrombus on LVAD is dissolved in 30 min, without damages on LVADs and organs. This IST exhibits to be more efficient and safer compared with other thrombolysis methods on LVAD. [ABSTRACT FROM AUTHOR]

Fibrin is found in both arterial and venous thrombi, which provides an important target for thrombus-targeted microbubbles (MBs) used in MB-enhanced ultrasound imaging and sonothrombolysis. A fibrin-targeted peptide, Cys-Arg-Glu-Lys-Ala (CREKA), is used to modify the commercially available SonoVue ultrasound contrast agent using a conjugation method, and the binding capacity and binding strength of the fibrin-targeted CREKA-modified SonoVue MBs are evaluated with a thrombus-embedded microchannel at a typical shear rate range of venous and arterial blood flow. The experimental results indicate that the targeted MBs bind firmly to the thrombus surface when they flow along the microchannel at a wall shear rate of up to 1000 s−1. This work not only provides an effective method for the fabrication of fibrin-targeted MBs based on commercially available SonoVue MBs but also demonstrates an approach for evaluation of the binding properties of flowing targeted MBs under well-controlled flow conditions. [ABSTRACT FROM AUTHOR]

We present the manipulation of oil, organic and gaseous chemicals by electrowetting-on-dielectric (EWOD) technology using aqueous-shell compound drops. We demonstrate that the transport and coalescence of viscous oil drops, the reaction of bromine with styrene in benzene solution, and the reaction of red blood cells with carbon monoxide bubbles can be accomplished using this method. [ABSTRACT FROM AUTHOR]

The erosion pits formed in an ultrasound vibration cavitation were compared to those corrosion pits formed in static water. Concentric iridescent rings around the erosion pit make it different from those corrosion pits. The distinct color and the α-FeOOH structure of the rings indicated that the iridescent rings were oxidization film formed under high temperature generated in the cavitation environment. According to the direct observation on the development of the iridescent rings under microscope, the formation of the iridescent rings was attributed to the repeated interactions between mechanical removal and high temperature oxidization during the cavitation erosion. This work also illustrated the synergistic effect of erosion-enhanced corrosion during the cavitation erosion. [ABSTRACT FROM AUTHOR]

Microcapillary devices with tapered constrictions were fabricated for the study of the features of the cavitation. The cavitation was induced by applying negative pressure at the outlet with opening the inlet to atmospheric pressure, and the experimental results show that the cavitation bubbles generated at the center of the tapered tip flow upstream and adhere on the wall near the orifice, which is explained by the recirculation flow according to the numerical simulation results. The desinent cavitation number keeps constant for a microcapillary device, and the device works in a negative-pressure system is more susceptible to the cavitation than that works in a positive-pressure system. In addition, the effect of the orifice size on the incipient cavitation number and the desinent cavitation number has been studied with five devices with different sizes of the orifices from 50 to 120 microns. Both the incipient and desinent cavitation numbers increase monotonely with the size of the orifice. These results may be helpful to the design of the geometries of the microfluidic devices for various applications. [ABSTRACT FROM AUTHOR]

A 100-h-long cavitation erosion experiment was performed on a sample of polytetrafluoroethelyene (PTFE). The weight loss curve of PTFE was different from that of metals, and the erosion process was characterized by two stages, each with a distinct erosion rate. Morphology studies on the erosion pits and X-ray diffraction analysis of the eroded surfaces revealed that brittle fracture was the main reason for the higher erosion rate at the beginning of the erosion process, while ductile fracture dominated the weight loss process later in the erosion process, thereby reducing the erosion rate. Based on these results, we consider that this transition from brittle to ductile fracture was responsible for the different erosion rates at the two different erosion stages. [ABSTRACT FROM AUTHOR]

Adhesion of marine fouling organisms on artificial surfaces such as ship hulls causes many problems, including extra energy consumption, high maintenance costs, and increased corrosion. Therefore, marine antifouling is an important issue. In this review, physical and biochemical developments in the field of marine biofouling, which involves biofilm formation and macro-organism settlement, are discussed. The major antifouling technologies based on traditional chemical methods, biological methods, and physical methods are presented. The chemical methods include self-polishing types such as tributyltin (TBT) self-polishing co-polymer coatings, which despite its good performance has been banned since 2008 because of its serious environmental impact. Therefore, other methods have been encouraged. These include coatings with copper compounds and biocide boosters to replace the TBT coatings. Biological extracts of secreted metabolites and enzymes are anticipated to act as antifoulants. Physical methods such as modification of surface topography, hydrophobic properties, and charge potential have also been considered to prevent biofouling. In this review, most of the current antifouling technologies are discussed. It is proposed that the physical antifouling technologies will be the ultimate antifouling solution, because of their broad-spectrum effectiveness and zero toxicity. [ABSTRACT FROM AUTHOR]

3D microparticles have promising applications in self-assembly, biomedical engineering, mechanical engineering, etc. The shape of microparticles plays a significant role in their functionalities. Although numerous investigations have been conducted to tailor the shape of microparticles, the diversity is still limited, and it remains a challenge to fabricate 3D microparticles with sharp edges. Here, we present a facile approach that combines a folded PDMS channel and orthogonal projection lithography for shaping sharp-edged 3D microparticles. By adjusting the number and the length of channel sides, both regular and irregular polyhedral cross-sections of the folded channel can be obtained. UV light with diverse patterns is applied vertically as the second shape controlling factor. A variety of 3D microparticles are obtained with sharp edges, which are potential templates for micromachining tools and abrasives. Some sharp-edged microparticles are assembled into 2D and 3D mesoscale structures, which demonstrates their prospective applications in self-assembly, tissue engineering, etc. [ABSTRACT FROM AUTHOR]

The rapid development of portable precision detection methods and the crisis of insufficient blood supply worldwide has led scientists to study mechanical visualization features beyond the biochemical properties of erythrocytes. Combined evaluation of currently known biochemical biomarkers and mechanical morphological biomarkers will become the mainstream of single-cell detection in the future. To explore the mechanical morphology of erythrocytes, a microfluidic capillary system was constructed in vitro, with flow velocity and glucose concentration as the main variables, and the morphology and ability of erythrocytes to recover from deformation as the main objects of analysis. We showed the mechanical distortion of erythrocytes under various experimental conditions. Our results showed that glucose plays important roles in improving the ability of erythrocytes to recover from deformation and in repairing the damage caused to the cell membrane during the repeated squeeze process. These protective effects were also confirmed in in vivo experiments. Our results provide visual detection markers for single-cell chips and may be useful for future studies in cell aging. [ABSTRACT FROM AUTHOR]

Deep vein thrombosis (DVT) often occurs in the lower limb veins of bedridden patients and greatly reduces the quality of life. The altered blood flow in venous valves induced by the insufficient efficacy of the muscle pump is commonly considered as a main factor. However, it is still a great challenge to observe the altered blood flow in real time, and its role in the formation of thrombi is poorly understood. Here we make a microfluidic venous valve model with flexible leaflets in a deformable channel that can mimic the motion of valves and the compression of vessels by muscle contraction, and identify the stasis and intermittent reflux in the valve pocket generated by the muscle pump. A thrombus forms in the stasis flow, while the intermittent reflux removes the fibrin and inhibits the growth of the thrombus. A flexible microfluidic device that can mimic the motion of valves and the contraction of vessels would have wide applications in the research on cardiovascular diseases. [ABSTRACT FROM AUTHOR]

This study demonstrates the use of a liquid-liquid phase reunion (PR) assisted sol-gel method to prepare hollow ZrO 2 microspheres. The oil phase of trichloroethylene and isooctanol mixture (TCE/IO), aqueous phase of the ZrO 2 precursor sol, and co-solvent phase propylene glycol monomethyl ether (PGME) were mixed and vigorously stirred to form an emulsion with dispersed sub-micron TCE/IO-rich droplets, which do not aggregate and are stable in the long term. This emulsion was further dispersed in pure TCE/IO to form multicore microdroplets, wherein the inner sub-micron droplets grew unstable and coalesced as one (PR), this led to the transformation of the microdroplets from being multicore to single core. The resultant core-shell structure was stable over the duration of the gelation and the aging processes. Subsequently, hollow ZrO 2 microspheres with cavities that could be size controlled were obtained by sintering. The method presented in this study is scalable for achieving an increased productivity due to the self-assembly fabrication of the core-shell droplets by using the liquid-liquid PR method. [ABSTRACT FROM AUTHOR]

A bubble in a vertical cylindrical capillary can get stuck due to the drainage of its lubrication film, according to the prediction originally made by Bretherton. When stuck, the profile of the lubrication film around the bubble is measured using an optical interference method. Our experimental results verified the theoretical prediction of the time-dependent minimum thickness hmin ∼ t−4/5 [C. Lamstaes and J. Eggers, "Arrested bubble 'rise' in a narrow tube," J. Stat. Phys. 167, 656–682 (2017)]. The bubble is stuck in a cylindrical capillary if the critical radius is proportional to the capillary length. We show that this result can be extended to square capillaries, where bubbles will get stuck in square capillaries below a critical width. For the same capillary length, the critical width of the square capillaries is much smaller than the critical radius of the cylindrical ones, due to the fluid leakage at the corners. As the square channels are also commonly used in microfluidic devices, our results provide helpful insights into the different features of the motion of bubbles resulting from the shape of channels. [ABSTRACT FROM AUTHOR]

Abstract: In this study, the diffusion‐induced external gelation is combined with a microfluidic technique to prepare monodisperse ZrO2 ceramic microspheres. The gelation of sol droplets is traced by fluorescence visualization of the local pH, and it illustrates the effect of the external concentration of triggering agent (tetramethylethylenediamine, TMEDA) on the formation of the gel network, which results in 3 kinds of deformation of the gel particles. The deformation mechanism mainly lies in the imbalanced Laplace pressure exerted on the gel network during the competition between the gelation and the drying processes. By regulating the concentration of TMEDA, the monodisperse ZrO2 ceramic microspheres with high sphericity can be readily fabricated. [ABSTRACT FROM AUTHOR]

Prolonged storage will alter the biophysical properties of red blood cells (RBCs), and it decreases the quality of stored blood for blood transfusion. It has been known that less deformable aged RBCs can be separated by margination, but the recognition of the storage time from the separation efficiency of the stiff RBCs is still a challenge. In this study, we realized enhanced separation of aged RBCs from normal RBCs by controlling the channel cross section and demonstrated that the storage time can be deduced from the percentage of the separated RBCs in the stored RBCs. This separation technology helps to reveal the regulation of time on the RBC aging mechanism and offer a new method to separate stiffened cells with high efficiency. [ABSTRACT FROM AUTHOR]

Ventricular assist devices (VADs) can effectively improve the survival rate of patients with end-stage heart failure, but the hemolytic complications induced by long-time VAD support have received wide attention recently. The conventional evaluation method of the hemolytic properties of VADs by the indicator of plasma free hemoglobin (PFH) concentration is used but not sensitive enough to meet the needs of the actual examinations. In this study, an experimental method was applied for the evaluation of the injuries and damages caused by VADs to erythrocytes by both indicators of PFH and lactic dehydrogenase (LDH) in the in vitro hemolysis assay of VADs. The changes of LDH and PFH concentrations in plasma with the shear stress and the exposure time under a fixed shear stress were measured and analyzed to investigate the sensitivity and accuracy of the evaluation of erythrocyte damage by LDH. Furthermore, through 24 h in vitro hemolysis tests, the changes of LDH and PFH concentrations in blood samples were measured in combination with the microscopic histological changes and ultrastructural changes of erythrocytes, to assess the possibility of LDH evaluating the hemolysis of VADs. The changes of the concentration of LDH were more sensitive than those of PFH to different shear stress and exposure times, especially lower stress. Meanwhile, in the 24 h in vitro hemolysis assay, the PFH concentration in the blood samples showed no significant changes in the first 8 h, while the LDH concentration increased significantly in the first 3 h, which was consistent with the morphological changes of erythrocytes. Compared with the changes of the PFH concentration, the LDH concentration is sensitive to the damage of erythrocytes caused by VADs. It was considered that LDH could be applied as an additional indicator in the evaluation of erythrocyte damage and hemolytic properties of VADs in combination with the normalized index of hemolysis, for the more accurate assessment of the blood compatibility of VADs. [ABSTRACT FROM AUTHOR]

A droplet micro-reactor was developed to realize the internal sol-gel reaction of ZrO2 inside the droplet. The reactants are only allowed to combine when the droplet forms, meanwhile, they are able to mix well and react to form gel particles with a proper designed structure of the micro-reactor. In this condition, the mixing efficiency was determined by the structure of the micro-reactor and the flow rate ratio of the two components. After sintering, ZrO2 ceramic microspheres are acquired with high sphericity and narrow size distribution. This droplet micro-reactor overcomes the gelation of the premixed sol and reactant in the channel, and it has been demonstrated to be more stable with a longer running time. [ABSTRACT FROM AUTHOR]

Drag reduction was found in polydimethylsiloxane (PDMS) microchannels when the flow was pulled by depressurization at the inlet, and it was attributed to the formation of the bubbles on the PDMS surface. The formed bubbles were examined by atomic force microscopy (AFM), and the resultant effective slip length was measured by micropimage velocimetry (μPIV). The drag reduction was found to decrease as the bubbles grew and detached from the surface, causing a pulsatile flow in the microchannel. [ABSTRACT FROM AUTHOR]

Porous carbon particles have been widely used in many areas including energy storage. Production of carbon microspheres in an efficient, controlled, and low-cost manner, however, is challenging. Here, we demonstrate a microfluidic approach to generate porous carbon particles using inexpensive precursors and show that the size of the particle and pores can be tuned by adjusting the deionized (DI) water content in droplets and preheating temperature. The developed strategy offers an effective approach to control the production of porous carbon spheres with a well-defined diameter, narrow size distribution and pore size. [ABSTRACT FROM AUTHOR]

A technology is presented to fabricate a microfluidic chip in which the microchannels and the microelectrodes of sensors are integrated directly into the copper sheet on a printed circuit board. Then, we demonstrate an application of the generation of oil-in-water and water-in-oil emulsion droplets on this microfluidic chip driven by a USB interface, and the droplet size is detected by the microelectrodes on the downstream microchannel. The integration of the microfluidic chip is improved by the direct connection of the channels to the microelectrodes of the driving unit and of the sensors on the same substrate, and it is a promising way to integrate microfluidics into a more complex micro electrical–mechanical system (MEMS). [ABSTRACT FROM AUTHOR]

Based on the self-developed experimental apparatus, the wet steam erosion experiments were performed on polished steel specimens. Scanning Electronic Microscope (SEM) and Atomic Force Microscope (AFM) were used to identify the pit characteristics. The experimental results showed that there was little damage on the surface after being impacted by wet steam erosion. However, when the micro-particles were added into the wet steam, not only indentations and scratches but also craters appeared on the eroded surface. Some characteristics of crater, such as the circular shape and intergranular fractures, make the damages distinguish from those of the water-drop or micro-particle impact to solid wall, and they are considered as the results of cavitation erosion. [ABSTRACT FROM AUTHOR]

To clarify the water erosion mechanism of the mild carbon steels, the water erosion experiments were performed by using deionized water as steam source. The results showed that under the damage threshold velocity of liquid impact, the material surface would not be destroyed. However, when the micro-particles were added into the steam, the pits appeared on the surface soon. By comparison, it is found that the pits are quite different from those induced by micro-particles impact without steam, but similar to those induced by cavitation erosion. The results indicated that the water erosion mechanism was similar to that of cavitation erosion under the damage threshold velocity. The micro-particles carry the micro-bubbles to approach the surface of the material, and the micro-bubbles collapse and generate micro-jet to impinge vertically on the surface, which lead to the produce of pits. [ABSTRACT FROM AUTHOR]