Functionalized alginate-based bioinks for microscale electrohydrodynamic bioprinting of living tissue constructs with improved cellular spreading and alignment

Bioprinting has been widely investigated for tissue engineering and regenerative medicine applications.However,it is still difficult to reconstruct the complex native cell arrangement due to the limited printing resolution of conventional bioprinting techniques such as extrusion-and inkjet-based printing.Recently,an electrohydrodynamic(EHD)bioprinting strategy was reported for the precise deposition of well-organized cell-laden constructs with microscale filament size,whereas few studies have been devoted to developing bioinks that can be applied for EHD bioprinting and simultaneously support cell spreading.This study describes functionalized alginate-based bioinks for microscale EHD bioprinting using peptide grafting and fibrin incorporation,which leads to high cell viability(>90%)and cell spreading.The printed filaments can be further refined to as small as 30μm by incorporating polyoxyethylene and remained stable over one week when exposed to an aqueous environment.By utilizing the presented alginate-based bioinks,layer-specific cell alignment along the printing struts could be observed inside the EHD-printed microscale filaments,which allows fabricating living constructs with cell-scale filament resolution for guided cellular orientation.

Non-contact tensile viscoelastic characterization of microscale biological materials

Many structures and materials in nature and physiology have important ＂meso-scale＂ structures at the micron lengthscale whose tensile responses have proven difficult to characterize mechanically. Although techniques such as atomic force microscopy and micro- and nano-identation are mature for compression and indentation testing at the nano-scale, and standard uniaxial and shear rheometry techniques exist for the macroscale, few techniques are applicable for tensile-testing at the micrometre-scale, leaving a gap in our understanding of hierarchical biomaterials. Here, we present a novel magnetic mechanical testing （MMT） system that enables viscoelastic tensile testing at this critical length scale. The MMT system applies non-contact loading, avoiding gripping and surface interaction effects. We demonstrate application of the MMT system to the first analyses of the pure tensile responses of several native and engineered tissue systems at the mesoscale, showing the broad potential of the system for exploring micro- and meso-scale analysis of structured and hierarchical biological systems.

APPLICATIONS AND MANUFACTURE OF THE MICROSCALE LONG-OPTICAL-PATH ELECTROCHEMICAL CELL WITH A PLUG-IN THIN-LAYER ELECTRODE

The construction and characteristics of a microscale long-optical-path electrochemi- cal cell with a plug-in thin-layer electrode are described.Using ferricyanide as the test species,the thermodynamic parameters of electron transfer processes are determined at car- bon,plantinum,and gold electrodes.

A basic model of unconventional gas microscale flow based on the lattice Boltzmann method

A new method for selecting dimensionless relaxation time in the lattice Boltzmann model was proposed based on similarity criterion and gas true physical parameters.At the same time,the dimensionless relaxation time was modified by considering the influence of the boundary Knudsen layer.On this basis,the second-order slip boundary condition of the wall was considered,and the key parameters in the corresponding combined bounce-back/specular-reflection boundary condition were deduced to build a new model of unconventional gas microscale flow simulation based on the lattice Boltzmann method suitable for high temperatures and high pressures.The simulation results of methane gas flow driven by body force in infinite micro-channels and flow driven by inlet-outlet pressure differential in long straight channels were compared with the numerical and analytical solutions in the literature to verify the accuracy of the model,and the dimensionless relaxation time modification was formally optimized.The results show that the new model can effectively characterize the slippage effect,compression effect,gas density and the effect of boundary Knudsen layer in the micro-scale flow of unconventional natural gas.The new model can achieve a more comprehensive characterization of the real gas flow conditions and can be used as a basic model for the simulation of unconventional gas flow on the micro-nano scale.

Investigation of normal,lateral,and oblique impact of microscale projectiles into unidirectional glass/epoxy composites

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(Do P)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 Do P, velocity, and penetration resistance force as functions of time. The theoretical model and numerical simulations are used to determine new Do P parameters: characteristic time of depth of penetration and threshold impact velocity. These models are a first step in developing the capability to predict Do P for oblique,microscale, high-speed impact on composite materials.

Microscale Infrared Observation of Liquid-Vapor Phase Change Process on the Surface of Porous Media for Loop Heat Pipe

Loop Heat Pipe (LHP) performance strongly depends on the performance of a wick that is porous media inserted in an evaporator. In this paper, the visualization results of thermo-fluid behavior on the surface of the wick with microscopic infrared thermography were reported. In this study, 2 different samples that simulated a part of wick in the evaporator were used. The wicks were made by different two materials: polytetrafluoroethylene (PTFE) and stainless steel (SUS). The pore radii of PTFE wick and SUS wick are 1.2 μm and 22.5 μm. The difference of thermo-fluid behavior that was caused by the difference of material was investigated. These two materials include 4 different properties: pore radius, thermal conductivity, permeability and porosity. In order to investigate the effect of the thermal conductivity on wick’s operating mode, the phase diagram on the q-keff plane was made. Based on the temperature line profiles, two operating modes: mode of heat conduction and mode of convection were observed. The effective thermal conductivity of the porous media has strong effect on the operating modes. In addition, the difference of heat leak through the wick that was caused by the difference of the material was discussed.

Developing From Tranditional Microscale Chemistry to Microscale Green Chemistry

Microscale chemistry is appealing to all levels of education.In contrast to conventional macroscale chemistry,only minute amount of chemicals are required to undertaking a chemical investigation.……

Microscale Chemistry in Japan

Microscale laboratory is environmentally benign as the amount of reagents,waste,energy and cost can be reduced dramatically,and exposure to potentially toxic chemicals is diminished.……

Microscale spherical TiO_(2)powder prepared by hydrolysis of TiCl_(4)solution:Synthesis and kinetics

Hydrolysis of TiCl_(4)solution is capable of preparing microscale TiO_(2)particles.This research studied the synthesis of microscale spherical TiO_(2)powders and the hydrolysis kinetics.The effects of the flow field generated by different agitators and baffles in the crystallizer,the initial free acid concentration,the initial equivalent TiO_(2)concentration,and the temperature on the hydrolysis progress and powder morphology were systematically studied.The results show that the flow field in a crystallizer can significantly affect the morphology and particle size of the powders,and the axial flow can improve the sphericity of the powders.The increased free HCl and equivalent TiO_(2)concentrations in the pregnant solution inhibit the forward hydrolysis reaction,prolong the time to reach equilibrium,and reduce the yield.An appropriate temperature matching the compositions of the pregnant solution is crucial for the powder morphology and size.Powders with sizes ranging from around 5 um-40μm can be tuned under controlled flow field,solution compositions,and temperature conditions.In addition,the Cheng and Wunderlich modified Avrami equation was used for the crystallization kinetic modeling.The effects of the free HCl concentration,equivalent TiO_(2)concentration,and hydrolysis temperature are reflected in the reaction rate constant and active nuclei reduction index.Increasing the free HCl and equivalent TiO_(2)concentrations will reduce the reaction rate constant and accelerate the deactivation of the active nuclei,thus increasing the final powder size,while increasing the temperature will lead to the opposite results.

Cell architecture designs towards high-energy-density microscale energy storage devices

The rapid growth of miniaturized electronics has led to an urgent demand for microscale energy storage devices(MESDs)to sustainably power the micro electronic devices.However,most MESDs reported to date have suffered from the limited energy densities and shape versatility compared to conventional large-scale counterparts because of the architectural constraints inherent in microfabrication-based cell manufacturing and cell dimension/structure.This review addresses the cell architecture design for MESDs that can achieve both miniaturization and high energy density.We provide a comprehensive overview of five types of cell architectures of MESDs and their fabrication techniques.In addition,to enable practical applications of MESDs,several cell design approaches are presented with the aim of minimizing the inactive parts of the cell and maximizing the performance metrics of MESDs.Finally,we discuss development direction and outlook of MESDs with a focus on materials chemistry,energy-dense electrochemical systems,and cell performance normalization,which will help to expand their applications and manufacturing scalability.

A rapid modeling method for urban microscale meteorology and its applications

This paper introduces a fast urban microscale meteorological model with a horizontal resolution of O(10)m,named URBAN(Urban Rapid&Building-Aware Neighborhood),which is capable of rapid assessment of meteorological fields over key urban areas,including wind speed,air temperature,humidity and thermal comfort index,with the execution time less than10 minutes consuming 1 CPU core.URBAN uses a fast wind diagnostic method to construct three-dimensional(3-D)wind fields surrounding complex building clusters with their geometry resolved explicitly.To enhance the accuracy of wind reconstruction and the continuity of the initial wind field around irregular buildings,we propose a new parameterization method based on stream functions,which can accurately characterize the influences of complex urban building clusters on the three-dimensional wind field.The model can provide various results for the meteorological service of large outdoor activities,including conventional meteorological elements(wind,temperature,humidity,radiation,etc.)and the Universal Thermal Comfort Index,which is derived from the relationship between physiological processes and environmental meteorological conditions.In this paper,URBAN is applied to develop an automatic analysis and forecast system of microscale meteorological elements over the central Beijing region in summer during a large outdoor event.By comparing with the half-hourly observations from three auto weather stations(AWSs)in the region,the root-mean-square errors(RMSEs)of the modeled 10-meter-height wind speed,2-meter-height air temperature and humidity are 0.98 m s^(-1),1.37℃and 7.37%,respectively.

Urban Earthquake Vulnerability Assessment and Mapping at the Microscale Based on the Catastrophe Progression Method

Vulnerability assessment and mapping play a crucial role in disaster risk reduction and planning for adaptation to a future earthquake.Turkey is one of the most at-risk countries for earthquake disasters worldwide.Therefore,it is imperative to develop effective earthquake vulnerability assessment and mapping at practically relevant scales.In this study,a holistic earthquake vulnerability index that addresses the multidimensional nature of earthquake vulnerability was constructed.With the aim of representing the vulnerability as a continuum across space,buildings were set as the smallest unit of analysis.The study area is in İzmit City of Turkey,with the exposed human and structural elements falling inside the most hazardous zone of seismicity.The index was represented by the building vulnerability,socioeconomic vulnerability,and vulnerability of the built environment.To minimize the subjectivity and uncertainty that the vulnerability indices based on expert knowledge are suffering from,an extension of the catastrophe progression method for the objective weighing of indicators was proposed.Earthquake vulnerability index and components were mapped,a local spatial autocorrelation metric was employed where the hotspot maps demarcated the earthquake vulnerability,and the study quantitatively revealed an estimate of people at risk.With its objectivity and straightforward implementation,the method can aid decision support for disaster risk reduction and emergency management.

Intermittent failure mechanism and stabilization of microscale electrical contact

The stability and lifetime of electrical contact pose a major challenge to the performance of microelectro-mechanical systems(MEMS),such as MEMS switches.The microscopic failure mechanism of electrical contact still remains largely unclear.Here conductive atomic force microscopy with hot switching mode was adopted to simulate the asperity-level contact condition in a MEMS switch.Strong variation and fluctuation of current and adhesion force were observed during 10,000 repetitive cycles,exhibiting an“intermittent failure”characteristic.This fluctuation of electrical contact properties was attributed to insulative carbonaceous contaminants repetitively formed and removed at the contact spot,corresponding to degradation and reestablishment of electrical contact.When contaminant film was formed,the contact interface became“metal/carbonaceous adsorbates/metal”instead of direct metal/metal contact,leading to degradation of the electrical contact state.Furthermore,a system of iridium/graphene on ruthenium(Ir/GrRu)was proposed to avoid direct metal/metal contact,which stabilized the current fluctuation and decreased interfacial adhesion significantly.The existence of graphene enabled less adsorption of carbonaceous contaminants in ambient air and enhanced mechanical protection against the repetitive hot switching actions.This work opens an avenue for design and fabrication of microscale electrical contact system,especially by utilizing two-dimensional materials.

A comprehensive review on microchannel heat sinks for electronics cooling

The heat generation of electronic devices is increasing dramatically,which causes a serious bottleneck in the thermal management of electronics,and overheating will result in performance deterioration and even device damage.With the development of micro-machining technologies,the microchannel heat sink(MCHS)has become one of the best ways to remove the considerable amount of heat generated by high-power electronics.It has the advantages of large specific surface area,small size,coolant saving and high heat transfer coefficient.This paper comprehensively takes an overview of the research progress in MCHSs and generalizes the hotspots and bottlenecks of this area.The heat transfer mechanisms and performances of different channel structures,coolants,channel materials and some other influencing factors are reviewed.Additionally,this paper classifies the heat transfer enhancement technology and reviews the related studies on both the single-phase and phase-change flow and heat transfer.The comprehensive review is expected to provide a theoretical reference and technical guidance for further research and application of MCHSs in the future.

Optical manipulation from the microscale to the nanoscale: fundamentals, advances and prospects

Since the invention of optical tweezers,optical manipulation has advanced significantly in scientific areas such as atomic physics,optics and biological science.Especially in the past decade,numerous optical beams and nanoscale devices have been proposed to mechanically act on nanoparticles in increasingly precise,stable and flexible ways.Both the linear and angular momenta of light can be exploited to produce optical tractor beams,tweezers and optical torque from the microscale to the nanoscale.Research on optical forces helps to reveal the nature of light–matter interactions and to resolve the fundamental aspects,which require an appropriate description of momenta and the forces on objects in matter.In this review,starting from basic theories and computational approaches,we highlight the latest optical trapping configurations and their applications in bioscience,as well as recent advances down to the nanoscale.Finally,we discuss the future prospects of nanomanipulation,which has considerable potential applications in a variety of scientific fields and everyday life.

VIBRATION ANALYSIS OF MICROSCALE PLATES BASED ON MODIFIED COUPLE STRESS THEORY

A non-classical Kirchhoff plate model is developed for the dynamic analysis of microscale plates based on the modified couple stress theory in which an internal material length scale parameter is included. Unlike the classical Kirchhoff plate model, the newly developed model can capture the size effect of microscale plates. Two boundary value problems of rectangular micro- plates are solved and the size effect on the lowest two natural frequencies is investigated. It is shown that the natural frequencies of the microscale plates predicted by the current model are size-dependent when the plate thickness is comparable to the material length scale parameter.

Microscale endometrial sampling biopsy in detecting endometrial cancer and atypical hyperplasia in a population of 1551 women:a comparative study with hysteroscopic endometrial biopsy

Background:Endometrial cancer is one of the most common malignancies of the reproductive system.Effective and cost-effective screening method for populations at high risk is not available.This study aimed to investigate specimen adequacy and the influencing factors in microscale endometrial sampling biopsy and to evaluate the diagnostic accuracy and medical cost of biopsy in endometrial cancer and atypical hyperplasia screenings in comparison with hysteroscopic endometrial biopsy.Methods:A total of 1551 patients at high risk for endometrial lesions who required hysteroscopic endometrial biopsy from November 2017 to August 2018 were included.Microscale endometrial sampling biopsy was performed,followed by hysteroscopic endometrial biopsy.We evaluated the specimen adequacy and influencing factors of microscale endometrial sampling.Diagnostic consistency between microscale endometrial sampling biopsy and hysteroscopic endometrial biopsy was evaluated.The sensitivity,specificity,positive predictive value,and negative predictive value of microscale endometrial sampling biopsy in screening for endometrial cancer and atypical hyperplasia were analyzed,and the medical costs of the two procedures were compared.Results:The specimen adequacy was 81.2%.Patient age,menopausal status,endometrial thickness,and endometrial lesion type were correlated with specimen adequacy.There was good consistency in distinguishing benign and malignant endometrial diseases between microscale endometrial sampling biopsy and hysteroscopic biopsy(kappa 0.950,95%CI 0.925-0.975).The sensitivity,specificity,positive predictive value,and negative predictive value of microscale endometrial sampling biopsy were 91.7%,100.0%,100.0%,and 99.3%for endometrial cancer screening,respectively,and 82.0%,100.0%,100.0%,and 99.4%for atypical hyperplasia screening.The medical cost of endometrial sampling biopsy was only 22.1%of the cost of hysteroscopic biopsy.Conclusions:Microscale endometrial sampling biopsy is a minimally invasive alternative technique for obtaining adequate endometrial specimens for histopathological examination.It has the potential to be used in detecting endometrial cancer and atypical hyperplasia with high efficiency and low cost.

Representation of microscale ocean wavenumber spectrum correct to the second order

In this paper, the analytical representations of four wave source functions in high-frequency spectrum range are given on the basis of ocean wave theory and dimensional analysis, and the perturbation method is used to solve the governing equations of ocean wave high-frequency spectrum on the basis of the temporally stationary and locally homogeneous scale relations of microscale wave. The microscale ocean wavenumber spectrum correct to the second order has an explicit structure, its first order part represents the equilibrium between dif- ferent source functions, and its second order part represents the contribution of microscale wave propagation.

A microscale optical implant for continuous in vivo monitoring of intraocular pressure

Intraocular pressure(IOP)is a key clinical parameter in glaucoma management.However,despite the potential utility of daily measurements of IOP in the context of disease management,the necessary tools are currently lacking,and IOP is typically measured only a few times a year.Here we report on a microscale implantable sensor that could provide convenient,accurate,ondemand IOP monitoring in the home environment.When excited by broadband near-infrared(NIR)light from a tungsten bulb,the sensor’s optical cavity reflects a pressure-dependent resonance signature that can be converted to IOP.NIR light is minimally absorbed by tissue and is not perceived visually.The sensor’s nanodot-enhanced cavity allows for a 3–5 cm readout distance with an average accuracy of 0.29 mm Hg over the range of 0–40 mm Hg.Sensors were mounted onto intraocular lenses or silicone haptics and secured inside the anterior chamber in New Zealand white rabbits.Implanted sensors provided continuous in vivo tracking of short-term transient IOP elevations and provided continuous measurements of IOP for up to 4.5 months.

Microscale mechanics for metal thin film delamination along ceramic substrates

The metal thin film delamination along metal/ceramic interface in the case of large scale yielding is studied by employing the strain gradient plasticity theory and the material microscale effects are considered. Two different f racture process models are used in this study to describe the nonlinear delamination phenomena for metal thin films. A set of experiments have been done on the mechanism of copper films delaminating from silica substrates, based on which the peak interface separation stress and the micro-length scale of material, as well as the dislocation-free zone size are predicted.