A novel integrated microfluidic chip for on-demand electrostatic droplet charging and sorting

On-demand droplet sorting is extensively applied for the efficient manipulation and genome-wide analysis of individual cells.However,state-of-the-art microfluidic chips for droplet sorting still suffer from low sorting speeds,sample loss,and labor-intensive preparation procedures.Here,we demonstrate the development of a novel microfluidic chip that integrates droplet generation,on-demand electrostatic droplet charging,and high-throughput sorting.The charging electrode is a copper wire buried above the nozzle of the microchannel,and the deflecting electrode is the phosphate buffered saline in the microchannel,which greatly simplifies the structure and fabrication process of the chip.Moreover,this chip is capable of high-frequency droplet generation and sorting,with a frequency of 11.757 kHz in the drop state.The chip completes the selective charging process via electrostatic induction during droplet generation.On-demand charged microdroplets can arbitrarilymove to specific exit channels in a three-dimensional(3D)-deflected electric field,which can be controlled according to user requirements,and the flux of droplet deflection is thereby significantly enhanced.Furthermore,a lossless modification strategy is presented to improve the accuracy of droplet deflection or harvest rate from 97.49% to 99.38% by monitoring the frequency of droplet generation in real time and feeding it back to the charging signal.This chip has great potential for quantitative processing and analysis of single cells for elucidating cell-to-cell variations.

Buckling Optimization of Curved Grid Stiffeners through the Level Set Based Density Method

Stiffened structures have great potential for improvingmechanical performance,and the study of their stability is of great interest.In this paper,the optimization of the critical buckling load factor for curved grid stiffeners is solved by using the level set based density method,where the shape and cross section(including thickness and width)of the stiffeners can be optimized simultaneously.The grid stiffeners are a combination ofmany single stiffenerswhich are projected by the corresponding level set functions.The thickness and width of each stiffener are designed to be independent variables in the projection applied to each level set function.Besides,the path of each single stiffener is described by the zero iso-contour of the level set function.All the single stiffeners are combined together by using the p-norm method to obtain the stiffener grid.The proposed method is validated by several numerical examples to optimize the critical buckling load factor.

Efficient Carbon-Based CsPbBr_3 Inorganic Perovskite Solar Cells by Using Cu-Phthalocyanine as Hole Transport Material

Metal halide perovskite solar cells(PSCs) have attracted extensive research interest for next-generation solution-processed photovoltaic devices because of their high solar-to-electric power conversion efficiency(PCE)and low fabrication cost. Although the world's best PSC successfully achieves a considerable PCE of over 20% within a very limited timeframe after intensive efforts, the stability, high cost, and up-scaling of PSCs still remain issues. Recently, inorganic perovskite material, CsPbBr_3, is emerging as a promising photo-sensitizer with excellent durability and thermal stability, but the efficiency is still embarrassing. In this work, we intend to address these issues by exploiting CsPbBr_3 as light absorber, accompanied by using Cu-phthalocyanine(CuPc) as hole transport material(HTM) and carbon as counter electrode. The optimal device acquires a decent PCE of 6.21%, over 60% higher than those of the HTM-free devices. The systematic characterization and analysis reveal a more effective charge transfer process and a suppressed charge recombination in PSCs after introducing CuPc as hole transfer layer. More importantly, our devices exhibit an outstanding durability and a promising thermal stability, making it rather meaningful in future fabrication and application of PSCs.

Bilateral Filter for the Optimization of Composite Structures

In the present study,we propose to integrate the bilateral filter into the Shepard-interpolation-based method for the optimization of composite structures.The bilateral filter is used to avoid defects in the structure that may arise due to the gap/overlap of adjacent fiber tows or excessive curvature of fiber tows.According to the bilateral filter,sensitivities at design points in the filter area are smoothed by both domain filtering and range filtering.Then,the filtered sensitivities are used to update the design variables.Through several numerical examples,the effectiveness of the method was verified.

A Parameter-Free Approach to Determine the Lagrange Multiplier in the Level Set Method by Using the BESO

A parameter-free approach is proposed to determine the Lagrange multiplier for the constraint of material volume in the level set method.It is inspired by the procedure of determining the threshold of sensitivity number in the BESO method.It first computes the difference between the volume of current design and the upper bound of volume.Then,the Lagrange multiplier is regarded as the threshold of sensitivity number to remove the redundant material.Numerical examples proved that this approach is effective to constrain the volume.More importantly,there is no parameter in the proposed approach,which makes it convenient to use.In addition,the convergence is stable,and there is no big oscillation.

Sensitivity Analysis of a Bioinspired Refractive Index Based Gas Sensor

It was found out that the change of refractive index of ambient gas can lead to obvious change of the color of Morpho butterfly＇s wing. Such phenomenon has been employed as a sensing principle for detecting gas. In the present study, Rigorous Coupled-Wave Analysis （RCWA） was described briefly, and the partial derivative of optical reflection efficiency with respect to the refractive index of ambient gas, i.e., sensitivity of the sensor, was derived based on RCWA. A bioinspired grating model was constructed by mimicking the nanostructure on the ground scale of Morpho didius butterfly＇s wing. The analytical sensitivity was verified and the effect of the grating shape on the reflection spectra and its sensitivity were discussed. The results show that by tuning shape parameters of the grating, we can obtain desired reflection spectra and sensitivity, which can be applied to the design of the bioinspired refractive index based gas sensor.

Buckling optimization of curvilinear fiber-reinforced composite structures using a parametric level set method

Owing to their excellent performance and large design space,curvilinear fiber-reinforced composite structures have gained considerable attention in engineering fields such as aerospace and automobile.In addition to the stiffness and strength of such structures,their stability also needs to be taken into account in the design.This study proposes a level-set-based optimization framework for maximizing the buckling load of curvilinear fiber-reinforced composite structures.In the proposed method,the contours of the level set function are used to represent fiber paths.For a composite laminate with a certain number of layers,one level set function is defined by radial basis functions and expansion coefficients for each layer.Furthermore,the fiber angle at an arbitrary point is the tangent orientation of the contour through this point.In the finite element of buckling,the stiffness and geometry matrices of an element are related to the fiber angle at the element centroid.This study considers the parallelism constraint for fiber paths.With the sensitivity calculation of the objective and constraint functions,the method of moving asymptotes is utilized to iteratively update all the expansion coefficients regarded as design variables.Two numerical examples under different boundary conditions are given to validate the proposed approach.Results show that the optimized curved fiber paths tend to be parallel and equidistant regardless of whether the composite laminates contain holes or not.Meanwhile,the buckling resistance of the final design is significantly improved.

VMMAO-YOLO:an ultra-lightweight and scale-aware detector for real-time defect detection of avionics thermistor wire solder joints

The quality of the exposed avionics solder joints has a significant impact on the stable operation of the inorbit spacecrafts.Nevertheless,the previously reported inspection methods for multi-scale solder joint defects generally suffer low accuracy and slow detection speed.Herein,a novel real-time detector VMMAO-YOLO is demonstrated based on variable multi-scale concurrency and multi-depth aggregation network(VMMANet)backbone and“one-stop”global information gather-distribute(OS-GD)module.Combined with infrared thermography technology,it can achieve fast and high-precision detection of both internal and external solder joint defects.Specifically,VMMANet is designed for efficient multi-scale feature extraction,which mainly comprises variable multi-scale feature concurrency(VMC)and multi-depth feature aggregation-alignment(MAA)modules.VMC can extract multi-scale features via multiple fix-sized and deformable convolutions,while MAA can aggregate and align multi-depth features on the same order for feature inference.This allows the low-level features with more spatial details to be transmitted in depth-wise,enabling the deeper network to selectively utilize the preceding inference information.The VMMANet replaces inefficient highdensity deep convolution by increasing the width of intermediate feature levels,leading to a salient decline in parameters.The OS-GD is developed for efficacious feature extraction,aggregation and distribution,further enhancing the global information gather and deployment capability of the network.On a self-made solder joint image data set,the VMMAOYOLO achieves a mean average precision mAP@0.5 of 91.6%,surpassing all the mainstream YOLO-series models.Moreover,the VMMAO-YOLO has a body size of merely 19.3 MB and a detection speed up to 119 frame per second,far superior to the prevalent YOLO-series detectors.

An M-VCUT level set-based data-driven model of microstructures and optimization of two-scale structures

The optimization of two-scale structures can adapt to the different needs of materials in various regions by reasonably arranging different microstructures at the macro scale,thereby considerably improving structural performance.Here,a multiple variable cutting(M-VCUT)level set-based data-driven model of microstructures is presented,and a method based on this model is proposed for the optimal design of two-scale structures.The geometry of the microstructure is described using the M-VCUT level set method,and the effective mechanical properties of microstructures are computed by the homogenization method.Then,a database of microstructures containing their geometric and mechanical parameters is constructed.The two sets of parameters are adopted as input and output datasets,and a mapping relationship between the two datasets is established to build the data-driven model of microstructures.During the optimization of two-scale structures,the data-driven model is used for macroscale finite element and sensitivity analyses.The efficiency of the analysis and optimization of two-scale structures is improved because the computational costs of invoking such a data-driven model are much smaller than those of homogenization.

Indium-doped perovskite-related cesium copper halide scintillator films for high-performance X-ray imaging

Scintillators are widely utilized in high-energy radiation detection in view of their high light yield and short fluorescence decay time.However,constrained by their current shortcomings,such as complex fabrication procedures,high temperature,and difficulty in the large scale,it is difficult to meet the increasing demand for costeffective,flexible,and environment-friendly X-ray detection using traditional scintillators.Perovskite-related cesium copper halide scintillators have recently received multitudinous research due to their tunable emission wavelength,high photoluminescence quantum yield(PLQY),and excellent optical properties.Herein,we demonstrated a facile solution-synthesis route for indium-doped all-inorganic cesium copper iodide(Cs_(3)Cu_(2)I_(5))powders and a high scintillation yield flexible film utilizing indium-doped Cs_(3)Cu_(2)I_(5)powders.The large area flexible films achieved a PLQY as high as 90.2%by appropriately adjusting the indium doping concentration,much higher than the undoped one(73.9%).Moreover,benefiting from low self-absorption and high PLQY,the Cs_(3)Cu_(2)I_(5):In films exhibited ultralow detection limit of 56.2 n Gy/s,high spatial resolution up to 11.3 lp/mm,and marvelous relative light output with strong stability,facilitating that Cs_(3)Cu_(2)I_(5):In films are excellent candidates for X-ray medical radiography.Our work provides an effective strategy for developing environment-friendly,low-cost,and efficient scintillator films,showing great potential in the application of highperformance X-ray imaging.

Filters for manufacturability in design optimization of variable stiffness composites

In the design optimization of variable stiffness composites,manufacturing constraints imposed by the automated fiber placement technology must be considered.In the present paper,two filters are proposed to address this issue,and they are incorporated into the Shepard interpolation-based design optimization framework developed in our previous studies.The fiber angle arrangement of a composite is represented by a continuous function that interpolates fiber angles at scattered design points.Two filters are appointed for each design point to deal with two typical manufacturing constraints,i.e.,fiber curvature and gap/overlap.At each design point,the sensitivity is first filtered in a rectangular region around this point,and by this means the fiber curvature is controlled;then in another rectangular region around this design point,the filtered sensitivities are averaged,and the result is used to update the corresponding design variable.Several numerical examples are investigated,and the results show that the proposed method is effective.

Investigation of Fog Collection on Cactus-inspired Structures

We demonstrate the application of cactus-inspired structures for fog collection. The drop-on-cone system is modeled to analyze Gibbs free-energy gradients, equilibrium positions and motion of drops. Normalized free energy and free energy gra- dient are presented to characterize barrel and clam-shell drops, revealing the relations of the driving force and wettability to the half-apex angle of the cones. Small half-apex angle results in long collecting length and weak driving force. Thus it is important for fog collection to balance the driving force and collecting length with a suitable half-apex angle. Fog collection experiments on cactus-inspired structures are conducted for verification. Inflection points around 1.1° are observed, where the fog collection ability is mainly limited by the weak driving force when below the inflection points, while increases with the collecting length when above the inflection points. These indicate that the half-apex angle at the inflection point is a compromise between the driving force and collecting length, agreeing with the normalized functions. The results also prove that the hydrophilic cones are more suitable for fog collection with regard to condensation and driving force. Our research offers design guidance for efficient fog collection structure.

Experimental Analysis of Microscale Laser Shock Processing on Metallic Material Using Excimer Laser

Microscale laser shock processing （μLSP）, also known as laser shock processing in microscale, is a technique that uses microscale focused laser beam to induce high pressure plasma and generates plastic deformation and compressive residual stress in target materials, thus improves fatigue or stress corrosion cracking resistance of MEMS （Micro Electromechanical Systems） devices made of such a material. Many works have been reported about the research and experiment for μLSP. But the diameters of 50-200 μm were used at the first time for this field, which was useful for treating micro-device components with larger area and curved surface. The excimer laser was used firstly on μLSP for shorter wavelength than that of used in previous researches. The determination method of laser spot size at micro-level spatial resolution was presented. Under these conditions, plastic deformation, the stress analysis and microhardness with different pulse number, pulse energy and pulse spacing were investigated. Especially the residual stress distribution with depth treated by #LSP, was first investigated. Experiment results showed that the material performance was improved remarkably after μLSP.

A partition of unity level set method with moving knot CS-RBFs for optimizing variable stiffness composites

A partition of unity level set method with moving knot Compactly Supported Radial Basis Functions(CS-RBFs)is proposed for optimizing variable stiffness composite structures.The iso-contours of a level set function are utilized to represent the curved fiber paths,and the tan-gent vector of the iso-contour defines the orientation of fiber.The level set function of the full design domain is constructed according to the Partition of Unity(POU)method by a set of local level set functions defined on an array of overlapping subdomains,and they are constructed by using the CS-RBFs.The positions of knots are iteratively changed during the optimization to improve the performance of composite structures.Several examples of compliance minimization are presented.

Controlling nested wrinkle morphology through the boundary effect on narrow-band thin films

We describe the formation of nested wrinkles created by the thermal mismatch between a narrow-band thin film and a compliant substrate.When a film is described as"narrow-band",it literally means that the film band width is much shorter than its length;more precisely,it means that the width is comparable with the wavelength of the wrinkles.A silicon mask was used during film sputtering to create narrow-band films on poly(dimethylsiloxane)substrate,thus creating regular boundaries to steer local stresses and control wrinkle morphology.Disordered nano-scale wrinkles were found nested within highly ordered micro-scale sinusoidal wrinkles.The formation of nested wrinkles was explained through the amplitude and wavelength saturation of nano-scale wrinkles.The disordered morphology of nano-scale wrinkles and the highly ordered morphology of microscale wrinkles were explained by using the boundary effect.

Analysis on annealing-induced stress of blind-via TSV using FEM

Copper-filled through silicon via （TSV） is a promising material owing to its application in high-density three-dimensional （3D） packaging. However, in TSV manufacturing, thermo-mechanical stress is induced during the annealing process, often causing reliability issues. In this paper, the finite element method is employed to investigate the impacts of via shape and SiO2 liner uniformity on the thermo-mechanical properties of copper-filled blind-via TSV after annealing. Top interface stress analysis on the TSV structure shows that the curvature of via openings releases stress concentration that leads to -60 MPa decrease of normal stresses, σxx and Cryy, in copper and -70 MPa decrease of σxx in silicon. Meanwhile, the vertical interface analysis shows that annealing-induced stress at the SiO2/Si interface depends heavily on SiO2 uniformity. By increasing the thickness of SiO2 linear, the stress at the vertical interface can be significantly reduced. Thus, process optimization to reduce the annealing-induced stress becomes feasible. The results of this study help us gain a better understanding of the thermo-mechanical behavior of the annealed TSV in 3D packaging. Keywords through silicon via （TSV）, annealing-induced stress, interface stress, plastic deformation, finite element method

Review on flexible perovskite photodetector:processing and

Next-generation optoelectronics should possess lightweight and flexible characteristics,thus conforming to various types of surfaces or human skins for portable and wearable applications.Flexible photodetectors as fundamental devices have been receiving increasing attention owing to their potential applications in artificial intelligence,aerospace industry,and wise information technology of 120,among which perovskite is a promising candidate as the light-harvesting material for its outstanding optical and electrical properties,remarkable mechanical flexibility,low-cost and low-temperature processing methods.To date,most of the reports have demonstrated the fabrication methods of the perovskite materials,materials engineering,applications in solar cells,light-emitting diodes,lasers,and photodetectors,strategies for device performance enhancement,few can be seen with a focus on the processing strategies of perovskite-based flexible photodetectors,which we will give a comprehensive summary,herein.To begin with,a brief introduction to the fabrication methods of perovskite(solution and vapor-based methods),device configurations(photovoltaic,photoconductor,and phototransistor),and performance parameters of the perovskite-based photodetectors are first arranged.Emphatically,processing strategies for photodetectors are presented following,including flexible substrates(i.e.,polymer,carbon cloth,fiber,paper,etc.),soft electrodes(i.e.,metal-based conductive networks,carbon-based conductive materials,and two-dimensional(2D)conductive materials,etc.),conformal encapsulation(single-layer and multilayer stacked encapsulation),low-dimensional perovskites(0D,1D,and 2D nanostructures),and elaborate device structures.Typical applications of perovskite-based flexible photodetectors such as optical communication,image sensing,and health monitoring are further exhibited to learn the flexible photodetectors on a deeper level.Challenges and future research directions of perovskite-based flexible photodetectors are proposed in the end.The purpose of this review is not only to shed light on the basic design principle of flexible photodetectors,but also to serve as the roadmap for further developments of flexible photodetectors and exploring their applications in the fields of industrial manufacturing,human life,and health care.

Real-time tool condition monitoring method based on in situ temperature measurement and artificial neural network in turning

Tool failures in machining processes often cause severe damages of workpieces and lead to large quantities of loss,making tool condition monitoring an important,urgent issue.However,problems such as practicability still remain in actual machining.Here,a real-time tool condition monitoring method integrated in an in situ fiber optic temperature measuring apparatus is proposed.A thermal simulation is conducted to investigate how the fluctuating cutting heats affect the measuring temperatures,and an intermittent cutting experiment is carried out,verifying that the apparatus can capture the rapid but slight temperature undulations.Fourier transform is carried out.The spectrum features are then selected and input into the artificial neural network for classification,and a caution is given if the tool is worn.A learning rate adaption algorithm is introduced,greatly reducing the dependence on initial parameters,making training convenient and flexible.The accuracy stays 90%and higher in variable argument processes.Furthermore,an application program with a graphical user interface is constructed to present real-time results,confirming the practicality.

Shape and topology optimization for tailoring the ratio between two flexural eigenfrequencies of atomic force microscopy cantilever probe

In an operation mode of atomic force micro- scopy that uses a higher eigenmode to determine the physical properties of material surface, the ratio between the eigenfrequency of a higher flexural eigenmode and that of the first flexural eigenmode was identified as an important parameter that affects the sensitivity and accessibility. Structure features such as cut-out are often used to tune the ratio of eigenfrequencies and to enhance the performance. However, there lacks a systematic and automatic method for tailoring the ratio. In order to deal with this issue, a shape and topology optimization problem is formulated, where the ratio between two eigenfrequen- cies is defined as a constraint and the area of the cantilever is maximized. The optimization problem is solved via the level set based method.