Precise assembly and joining of silver nanowires in three dimensions for highly conductive composite structures

Three-dimensional(3D)electrically conductive micro/nanostructures are now a key component in a broad range of research and industry fields.In this work,a novel method is developed to realize metallic 3D micro/nanostructures with silver-thiol-acrylate composites via two-photon polymerization followed by femtosecond laser nanojoining.Complex 3D micro/nanoscale conductive structures have been successfully fabricated with∼200 nm resolution.The loading of silver nanowires(AgNWs)and joining of junctions successfully enhance the electrical conductivity of the composites from insulating to 92.9 Sm^−1 at room temperature.Moreover,for the first time,a reversible switching to a higher conductivity is observed,up to∼10^5Sm^−1 at 523 K.The temperature-dependent conductivity of the composite is analyzed following the variable range hopping and thermal activation models.The nanomaterial assembly and joining method demonstrated in this study pave a way towards a wide range of device applications,including 3D electronics,sensors,memristors,micro/nanoelectromechanical systems,and biomedical devices,etc.

Precise assembly of inside-out cell membrane camouflaged nanoparticles via bioorthogonal reactions for improving drug leads capturing

Cell membrane camouflaged nanoparticles have been widely used in the field of drug leads discovery attribute to their unique biointerface targeting function.However,random orientation of cell membrane coating does not guarantee effective and appropriate binding of drugs to specific sites,especially when applied to intracellular regions of transmembrane proteins.Bioorthogonal reactions have been rapidly developed as a specific and reliable method for cell membrane functionalization without disturbing living biosystem.Herein,inside-out cell membrane camouflaged magnetic nanoparticles(IOCMMNPs)were accurately constructed via bioorthogonal reactions to screen small molecule inhibitors targeting intracellular tyrosine kinase domain of vascular endothelial growth factor recptor-2.Azide functionalized cell membrane acted as a platform for specific covalently coupling with alkynyl functionalized magnetic Fe_(3)O_(4)nanoparticles to prepare IOCMMNPs.The inside-out orientation of cell membrane was successfully verified by immunogold staining and sialic acid quantification assay.Ultimately,two compounds,senkyunolide A and ligustilidel,were successfully captured,and their potential antiproliferative activities were further testified by pharmacological experiments.It is anticipated that the proposed inside-out cell membrane coating strategy endows tremendous versatility for engineering cell membrane camouflaged nanoparticles and promotes the development of drug leads discovery platforms.

An image mosaic technique with non-overlapping regions based on microscopic vision in precision assembly

Microscopic vision has been widely applied in precision assembly.To achieve sufficiently high resolution in measurements for precision assembly when the sizes of the parts involved exceed the field of view of the vision system,an image mosaic technique must be used.In this paper,a method for constructing an image mosaic with non-overlapping areas with enhanced efficiency is proposed.First,an image mosaic model for the part is created using a geometric model of the measurement system installed on a X-Y-Z precision stages with high repeatability,and a path for image acquisition is established.Second,images are captured along the same path for a specified calibration plate,and an entire image is formed based on the given model.The measurement results obtained from the specified calibration plate are utilized to identify mosaic errors and apply compensation for the part requiring measurement.Experimental results show that the maximum error is less than 4μm for a camera with pixel equivalent 2.46μm,thereby demonstrating the accuracy of the proposed method.This image mosaic technique with non-overlapping regions can simplify image acquisition and reduce the workload involved in constructing an image mosaic.

Precise and Controllable Assembly of Block Copolymers

With the development of nanotechnology,the precise synthesis of nanoparticles with nicely-defined dimensions and structures has been well-developed,and the functionalization and subsequent applications of the resultant nanostructures are becoming increas-ingly important.Comparing to inorganic nanoparticles,the nanostructures based on soft matters,especially block copolymer as-semblies,are much lower in cost,easier to fabricate and richer in morphology.However,the dimensional control over the block co-polymer assemblies is not as easy.Only in recent decade,with the discovery of living Crystallization-Driven Self-Assembly(CDSA)by Manners and Winnik,researchers become able to precisely tune the sizes of block copolymer assemblies in a relatively wide range.This discovery has inspired tremendous research effort in the self-assembly field,and considerable progress has been made recently.This review summarizes the main progress in the precise and controllable self-assembly field in the past five years,and is mostly fo-cused on four aspects,including in-depth understanding of the assembly methods,extension of this method to two-dimensional nanostructures,utilization of this method to fabricate hierarchical structures,and the potential applications of these well-defined nanostructures.We hope not only to make a periodic systematic summary of previous studies,but also to provide some useful thinking for the future development of this field.

Optimizing circumferential assembly angle of rotor parts connected by curvic couplings based on acquired tooth surface error data

Due to the excellent self-centering and load-carrying capability,curvic couplings have been widely used in advanced aero-engine rotors.However,curvic tooth surface errors lead to poor assembly precision.Traditional physical-master-gauge-based indirect tooth surface error measurement and circumferential assembly angle optimization methods have the disadvantages of high cost and weak generality.The unknown tooth surface fitting mechanism is a big barrier to assembly precision prediction and improvement.Therefore,this work puts forward a data-driven assembly simulation and optimization approach for aero-engine rotors connected by curvic couplings.The origin of curvic tooth surface error is deeply investigated.Using 5-axis sweep scan method,a large amount of high-precision curvic tooth surface data are acquired efficiently.Based on geometric models of parts,the fitting mechanism of curvic couplings is uncovered for assembly precision simulation and prediction.A circumferential assembly angle optimization model is developed to decrease axial and radial assembly runouts.Experimental results show that the assembly precision can be predicted accurately and improved dramatically.By uncovering the essential principle of the assembly precision formation and proposing circumferential assembly angle optimization model,this work is meaningful for assembly quality,efficiency and economy improvement of multistage aero-engine rotors connected by curvic couplings.

Macroscopic Supramolecular Assembly and Its Applications

Macroscopic supramolecular assembly(MSA)has been a recent progress in supramolecular chemistry.MSA mainly focuses on studies of the building blocks with a size beyond ten micrometers and the non-covalent interactions between these interactive building blocks to form ordered structures.MSA is essential to realize the concept of"self-assembly at all scales"by bridging most supramolecular researches at molecular level and at macroscopic scale.This review summaries the development of MSA,the basic design principle and related strategies to achieve MSA and potential applications.Correspondingly,we try to elucidate the correlations and differences between"macroscopic assembly"and MSA based on intermolecular interactions;the design principle and the underlying assembly mechanism of MSA are proposed to understand the reported MSA behaviors;to demonstrate further applications of MSA,we introduce some methods to improve the ordered degree of the assembled structures from the point of precise assembly and thus envision some possible fields for the use of MSA.

Effects of assembly errors and bonding defects on the centroid drift of a precision sleeve structure

Adhesive joints are widely used in precision electromechanical products,and their bonding process has significant effects on the performance of an assembled product.This paper presents a numerical study on the bonding assembly of a sleeve structure of a precision inertial device using a finite element method,where the stresses due to curing and relaxation behaviors are considered.The effects of assembly errors and bonding defects on the centroid drift of the sleeve structure were found and analyzed quantitatively.This study can help understand the zero-drift mechanism of the precision inertial device and contribute valuable data for its error compensation.