Precision Micro Research Articles

Exploring high-connectivity three-dimensional covalent organic frameworks: topologies, structures, and emerging applications.

Covalent organic frameworks (COFs) represent a highly versatile class of crystalline porous materials, formed by the deliberate assembly of organic building units into ordered two-dimensional (2D) and three-dimensional (3D) structures. Their unique combination of topological precision and tunable micro- or mesoporous architectures offers unmatched flexibility in material design. By selecting specific building units, reactive sites, and functional groups, COFs can be engineered to achieve customized skeletal, porous, and interfacial properties, opening the door to materials with optimized performance for diverse applications. Among recent advances, high-connectivity 3D COFs have emerged as a particularly exciting development, with their intricate network structures enabling unprecedented levels of structural complexity, stability, and functionality. This review provides a comprehensive overview of the synthesis strategies, topological design principles, structural characterization techniques, and emerging applications of high-connectivity 3D COFs. We explore their potential across a broad range of cutting-edge applications, including gas adsorption and separation, macromolecule adsorption, dye removal, photocatalysis, electrocatalysis, lithium-sulfur batteries, and charge transport. By examining these key areas, we aim to deepen the understanding of the intricate relationship between structure and function, guiding the rational design of next-generation COF materials. The continued advancements in this field hold immense promise for revolutionizing sectors such as energy storage, catalysis, and molecular separation, making high-connectivity 3D COFs a cornerstone for future technological innovations.

Measurement Methods for Droplet Adhesion Characteristics and Micrometer-Scale Quantification of Contact Angle on Superhydrophobic Surfaces: Challenges and Opportunities.

Inspired by nature, superhydrophobic surfaces have been widely studied. Usually the wettability of a superhydrophobic surface is quantified by the macroscopic contact angle. However, this method has various limitations, especially for precision micro devices with superhydrophobic surfaces, such as biomimetic artificial compound eyes and biomimetic water strider robots. These precision micro devices with superhydrophobic surfaces proposed a higher demand for the quantification of contact angles, requiring contact angle quantification technology to have micrometer-scale measurement capabilities. In this review, it is proposed to achieve micrometer-scale quantification of superhydrophobic surface contact angles through droplet adhesion characteristics (adhesion force and contact radius). Existing contact angle quantification techniques and droplet characteristics' measurement methods were described in detail. The advancement of micrometer-scale quantification technology for the contact angle of superhydrophobic surfaces will enhance our understanding of superhydrophobic surfaces.

Optimization of forward pulsed currents for combining the precision shaping and polishing of nickel micro mould tools to reduce demoulding defects

Precise tooling is vital for defect-free production of micro injection moulded (μ-IM) or hot-embossed products. The demoulding stage of such moulding and forming processes poses a serious challenge to the integrity of thin miniature features because of friction, adhesion, and thermal stresses. Typically, micro moulds involve geometrically textured patterns or features such as linear ridges, pillars, channels, and holes, the characteristic dimensions of which range from 10 to 300 μm. Realistically complex mould designs, containing precision micro features (enhanced fillet radius and positive draft angle) and high surface quality, are presented in this work. Electropolishing based on forward pulse currents (PC) has been used to shape and polish Ni micro moulds that contain sets of micron-scaled linear ridges and star patterns in order to ease the separation of moulded polymeric parts from the metallic mould during ejection and demoulding. The use of forward pulsed currents improved the mould design by increasing the fillet radii and draft angle while keeping the surface roughness low and maintaining a good surface shine. An optimization study of forward PC using a green solution of nickel sulfamate varied EP times (0–70 min) and duty cycles (40, 50, 60, and 70%) at a process conditions of 2.8 V, 50 °C, and 250 rpm. The best topographical and morphological changes were observed for a typical microfluidic channel (w × h, 100 × 110 μm) with an EP time of 70 min and 50% duty cycle: fillet radius increased by 3.8 μm, draft angle by 3.3°, and the channel width reduced by 11.4% while surface roughness changed by 8.6% and surface shine improved by 48.9%. Experimental validation was performed using hot embossing wherein the electropolished Ni mould replicated the micro channels and star patterns in PMMA chips with notably fewer burrs, material pile up, and no feature distortion. Moreover, there was a reduction in the side wall roughness of micro channels in PDMS casting with electropolished Ni mould by 16%. Hence, this work presents a significant scientific contribution to improving the efficiency of micro mould tools and reduces the defects caused by friction and adhesion in replicated polymeric parts.

Research and Exploration of Terahertz Feeder Manufacturing Technology Based on Micro-precision Machining

With the development of radar towards high frequency, the demand for terahertz waveguides and other devices is gradually increasing. But it is difficult to prepare such high-precision micro-devices by conventional processing methods. This paper summarizes several micromachining methods commonly used in terahertz feeder devices. On this basis, according to the development requirements of a certain type of terahertz waveguide with the characteristic of single-input-four-output, an experimental exploration is carried out. In the development process, the methods of precision NC machining and micro electroforming are comprehensively applied. which breaks through the difficulties of reliable transfer of surface coating and efficient dissolution of micro mold. The sample that meets dimensional accuracy and microwave performance was successfully prepared. The scheme has a reasonable process setting and can promote the engineering application of terahertz waveguide devices.

Predictive Analysis of Adverse Drug effects using Machine Learning

Abstract: The objective of this work is to develop machine learning (ML) methods that can accurately predict adverse drug reactions (ADRs) using databases like SIDER (Side Effect Research) and OFFSIDES (Government medical records). In this paper, three Machine Learning algorithms SVM (Support Vector Machine), Random Forest, and Gradient boosted trees are implemented on the datasets to predict various disorders caused due to adverse effects, and the performance is evaluated based on performance metrics such as average precision, recall, accuracy, f1 binary, f1 macro, and f1 micro. Finally, the two datasets were merged to understand and compare the performance of a combined dataset to a single dataset.

Multi-pulse agglomeration effects on ultrashort pulsed direct laser interference patterning of Cu

Surface functionalization by biomimetic patterns in the micro- and nanometer scale is well-established in a wide range of applications. The finely tuned surface properties are directly related to both primary and sub-pattern morphology of the applied topographies, which must be well-adjusted for maximum functionalization efficiency. In this light, the role of proceeding surface modification and its effect on pattern formation alongside multi-pulse ultrashort pulsed direct laser interference patterning (USP-DLIP) of Cu are investigated in detail by applying a multi-method characterization approach. It was shown that aside of topographical remodeling, USP-DLIP processing parallelly affects chemistry and the mechanical deformation state of the substrate surface, which in turn considerably influences laser/material interaction via incubation. An in-depth investigation of the individual and combined impacts of these substrate alterations on localized optical absorptance reveals how primary and sub-pattern formation dynamically respond to process induced surface modification. The DLIP-specific incubation impact on pattern morphology increases with inverted relation to pattern scale. The findings of this study provide a profound insight in the predominant physical interactions involved in pattern formation arising from the mutual influence between laser irradiation and substrate modification during USP-DLIP-processing of Cu allowing for high precision micro- and nanometer scaled pattern design.

Nanofiber Aerogels with Precision Macrochannels and LL-37-Mimic Peptides Synergistically Promote Diabetic Wound Healing.

Fast healing of diabetic wounds remains a major clinical challenge. Herein, this work reports a strategy to combine nanofiber aerogels containing precision macrochannels and the LL-37-mimic peptide W379 for rapid diabetic wound healing. Nanofiber aerogels consisting of poly(glycolide-co-lactide) (PGLA 90:10)/gelatin and poly-p-dioxanone (PDO)/gelatin short electrospun fiber segments were prepared by partially anisotropic freeze-drying, crosslinking, and sacrificial templating with three-dimensional (3D)-printed meshes, exhibiting nanofibrous architecture and precision micro-/macrochannels. Like human cathelicidin LL-37, W379 peptide at a concentration of 3 μg/mL enhanced the migration and proliferation of keratinocytes and dermal fibroblasts in a cell scratch assay and a proliferation assay. In vivo studies show that nanofiber aerogels with precision macrochannels can greatly promote cell penetration compared to aerogels without macrochannels. Relative to control and aerogels with and without macrochannels, adding W379 peptides to aerogels with precision macrochannels shows the best efficacy in healing diabetic wounds in mice in terms of cell infiltration, neovascularization, and re-epithelialization. The fast re-epithelization could be due to upregulation of phospho-extracellular signal-regulated kinase (p38 MAPK) after treatment with W379. Together, the approach developed in this work could be promising for the treatment of diabetic wounds and other chronic wounds.

A review of sequential micro-machining: State of art approach

In the recent years, a sequential micromachining is attracting attention of researchers as it is most promising structured approach to combine and utilize advantages of different types of micromachining techniques which improves the productivity in manufacture of high precision micro features of most advanced components. Sequential micromachining is a most effective recent approach to fabricate micro features of sophisticated parts to minimize drawbacks of individual machining techniques if they were used individually. In general, this technique combines the individual micro machining techniques in a logical sequence stages to machine faster with rough cuts in the former and achieve final sizes and tolerances in the later stage. It is the opposite of hybrid micro machining in which two techniques are combined together. Sequential micromachining can be done on different machine tools or preferably on the same machine tool for better work settling accuracy, low production time and hence less rejection. Thus, it is leading to manufacture of multifunction machine centers to perform sequential micromachining on the same machine. Eventually its necessities this manufacture to be more flexible and dynamic to accommodate the future requirements in a better way. The main aim of this review paper is to give latest developments in the field of sequential micromachining processes, especially done with same machine tools and their usefulness in terms of advantages, productivity, and applications. It also gives emphasis on capabilities of future possible combinations of various techniques with high potential in this domain.

Simulation analysis of titanium alloy micro-drilling based on thermo-mechanical coupling

With the increasing demand for high precision micro parts in machining field, the development of micro hole drilling technology, especially the finite element simulation technology is rapidly promoted. However, there are many limitations in the simulation of micro-drilling, such as element size, computational efficiency, chip forming, etc. In the present work, a finite element software, Abaqus has been used to simulate the thermal-mechanical coupling micro-drilling process of titanium alloy material, and the key technologies, such as twist bit modeling, material constitutive model, chip separation criterion and element division, were investigated. Through simulation, it was found that with the increase of rotational speed and the decrease of feed speed, chip shape gradually fragmented, in addition, thrust force and torque diminished. Since chip shape, thrust force and torque are important factors affecting drilling quality and tool life, the work could offer important guiding significance for cutting parameter optimization.

Developing Meso and Microholes by Spark-Erosion Based Drilling Processes: A Critical Review.

The increased demand for miniature components has drawn the attention of researchers, engineers, and industry users to manufacture precision micro and mesoholes on foils, sheets, and plates made from a variety of engineering materials. These days, micro-drilling is extensively being adopted as a fundamental operation in all kinds of smart manufacturing industries to make different types of microholes, such as through holes, blind holes, and taper holes on micro-parts and components. Drilled holes with a diameter of less than 1 mm are referred to as microholes, while drilled holes whose diameter ranges between 1 and 10 mm are known as mesoholes. Meso and microholes are commonly referred to as fine-holes. Modern or advanced drilling processes are mostly used to drill microholes from a variety of materials. This paper presents an extensive review of the previous research conducted on the drilling of fine holes (meso and micro size) by spark- erosion-based processes along with highlighting work and tool electrode materials, specifications of drilled holes, types of microholes (through or blind holes), process parameters, performance measures, and key findings. The paper aims to facilitate researchers and scholars by highlighting the capabilities of spark erosion machining, drilling, and its variants to fabricate miniature holes. The paper ends with a conclusion and future research directions to encourage further work in this area.

Investigating flank face friction during precision micro cutting of commercially pure titanium via plunging tests with diamond grooving tools

This study investigates flank face friction while micro machining commercially pure titanium (cp-Ti grade 2) work material considering size effects. It is important to understand friction phenomena at the tool flank and work material surface since they affect the surface integrity of the machined parts. A single crystal diamond grooving tool is used in machining experiments to reduce the influence of cutting edge radius. In addition, plunging type of cutting experiments were performed to investigate the influence of flank face contact on the machined surface. A friction model which is based on work and tool material properties is proposed to model the contribution of adhesion and deformation of the flank face coefficient of friction. The results show that for the cp-Ti and diamond tool pair, adhesion seems to be the dominant model of friction and also contributes to the size effect. The deformation friction becomes more dominant during the chip formation stage. When cutting edge effect is eliminated, the influences of flank and rake face friction on the size effect are shown.

A model-based investigation of tool-chip friction during precision micro cutting of commercially pure titanium alloy

Understanding interaction between the cutting tool edge radius and the work material is essential to identify the conditions leading to superior surface finish during the micromachining process. The interaction between friction angle and effective rake angle has been investigated based on a slip-line field-based machining model from the literature. Machining forces and cut chip thickness values were obtained from orthogonal cutting tests and employed in the process model. The proposed model also allows for calculating material properties such as shear flow stress and fracture toughness. The proposed model can successfully simulate machining forces during shearing-dominated machining conditions. The results showed the importance of flank and rake face friction in micro-scale machining.

An overview on parametric study of photochemical machining process and its applications

Photochemical Machining (PCM) is a well-known tightly controlled selective corrosion technique used to manufacture several micro and nano-size components high in quality and high precision; as it is a non-contact process, it gives a burr-free stress-free surface of the material. Nowadays, PCM is widely used in various industrial applications, including medical and healthcare industries, electronics, precision micro, nano, and other engineering industries. This article describes the correlation between various process parameters like etching temperature, time, and concentration of etchant with some response parameters like surface roughness value, metal removal rate (MRR), undercut (Uc), etch rate. In addition, magnetic field-assisted PCM and ultrasonic-assisted PCM are also explored in detail. The article highlights that etchant concentration and etching time play the most critical role in the PCM process. This article also depicts that with the increase in etchant temperature and etching time, the MRR and undercut increases. The article suggests future scopes and challenges of photochemical machining process.

Study of ion transportation and electrodeposition under hybrid agitation for electroforming of variable aspect ratios micro structures

Microstructural replication accuracy in precision micro electroforming process is related to ions transportation inside the micro structure and microstructural feature width and aspect ratio. In this study, a novel star pattern having a varying feature width of 20–320 μm with a corresponding aspect ratio of 5–0.3125 is proposed to characterize ion transportation and electrodeposition for electroforming of micro structures under a hybrid agitation of cathode rotation and jetting. Using designed patterns, simulations and electroforming experiments are conducted to systematically investigate the effect of flow fields on the diffusion layer thickness and current density on the microstructural filling precision. The results demonstrate that a hybrid flow combining cathode rotation and jetting can significantly enhance mass transfer with a ~33% reduction of diffusion layer thickness inside the micro structure with a high aspect ratio of 5, compared to individual rotating or jetting flow. The diffusion-based mass transfer is dominated inside the micro structure with an aspect ratio is greater than 1, where maximum relative replication error of depth is up to ~21.5% with an aspect ratio of 5. With the aspect ratio less than 1, the convection-dominated mass transfer can be significantly enhanced, where the minimum relative replication error of depth decreases to ~0.1%. The hybrid agitation is proved to be effective to supply ions for electrodeposition of micro structures. Additionally, the results also indicate that a low current density of 18 A/m2 should be used for defect-free electroforming of high-aspect-ratio micro structures based on hybrid agitation.

Investigation of mass transfer inside micro structures and its effect on replication accuracy in precision micro electroforming

Micro electroforming is a promising electrodeposition-based precision replication technique for the fabrication of microstructured moulds. In this process, a poor mass transfer inside the micro structure with a high aspect ratio significantly affects the replication accuracy of the mould. In this paper, a novel star pattern with a continuously changing line width in the range of 20–320 μm, corresponding to a variable aspect ratio of 0.16–2.5, was firstly proposed for the assessment of mass transfer capability and microstructural replication accuracy. Based on the designed patterns, the effects of different flow fields (cathode rotating/jetting agitation) on the ion concentration distribution and thickness of the diffusion layer were investigated theoretically. Our simulation indicated that nickel ion transportation was determined by convection and diffusion, depending on the width and aspect ratio of the micro structure. When the aspect ratio was higher than 1, the diffusion of nickel ions dominated the mass transfer. When a hybrid agitation combining cathode rotating and jetting flow was applied, the mass transfer of nickel ions inside a high-aspect-ratio micro structure achieved a 50% decrease in the thickness of the diffusion layer compared with individual rotating or jetting agitation. This will significantly affect the replication accuracy. Star-pattern micro electroforming experiments with the hybrid agitation were conducted to validate the effect of mass transfer on the pattern replication accuracy. The results indicated that the maximum replication relative error of the height and aspect ratio was ~16% and ~10%, respectively, with a designed high aspect ratio of 2.5 at a feature width of 20 μm. Both experiments and simulations consistently indicated that the thickness of the diffusion layer determined the replication accuracy of high-aspect-ratio features, in which the limiting current density was constrained by the thickness of the diffusion layer because of the ion transportation efficiency. Hybrid agitation can effectively reduce the thickness of the diffusion layer inside high-aspect-ratio feature, thus increasing the limiting current density. This can effectively increase the replication accuracy of high-aspect-ratio micro structures using micro electroforming.

Position sensor for active magnetic bearing with commercial linear optical encoders

Active magnetic bearings are used in a number of applications but their disadvantage is the high asynchronous error due to sensor noise amplification. In this paper a new radial position sensor for active magnetic bearings (AMB) based on linear optical encoders is presented. A commercial encoder scanning head faces a round scale with concentric, coplanar lines on its face. Because such a scale is not readily available, it is made by high precision micro machining and different options are compared. In experiments a measurement noise of 3.5 nm at 10 kHz bandwidth is achieved. In addition, a magnetic bearing is built to demonstrate the sensor in closed-loop.

Somatotype identification of middle-aged women based on decision tree algorithm

PurposeBody type classification has a great influence on plate making and garment sizing system, and the accuracy of body type classification method will greatly affect the fit of garment production. The purpose of this paper is to use the decision tree algorithm to study body classification rules, develop a decision tree body recognition model and judge the body shape of middle-aged women in Xinjiang.Design/methodology/approachFirst, perform dimensionless processing on the collected data of 256 middle-aged women in Xinjiang, and the dimensionless data were used for K-means body clustering; Then, quantitatively analyze the effectiveness of different classification clusters based on the silhouette coefficients. Second, the decision tree algorithm is used to divide the classified sample data into a training set and a test set at a ratio of 70/30, and select the best node and the best branch based on the Gini coefficient to construct a classification tree. Last, the overall optimal decision tree is generated by means of hyperparameter pruning.FindingsThe body shape of middle-aged women in Xinjiang can be divided into three types: standard body, plump body and obese body. The decision tree model has an excellent effect on body classification of middle-aged women in Xinjiang (precision (macro), 95.46%; precision (micro), 95.95%; recall (macro), 95.46%; recall (micro), 95.95%; F1 (macro), 95.46%; F1 (micro), 95.95%).Originality/valueFor scientific research, this paper is conducive to increasing the regional body type theory and stimulating the establishment of a garment sizing subdivision system in Xinjiang. In terms of production practice, this paper not only establishes a model for judging the shape of middle-aged women in Xinjiang, but also provides reference data for intermediates of various sizes. In addition, to facilitate pattern-making and the establishment of a subdivision system for the size of middle-aged women's garments in Xinjiang, this paper provides the grading values of various body control parts of middle-aged women in Xinjiang.

Surface tension—based ultra-micro precision dispensing method for micro—scale manufacturing and its key influence factors analysis

Due to the rapid development of precision micro-manufacturing technology, the connection and assembly process of precision micro devices put forward higher requirements for the volume and accuracy of micro dispensing technology. In this paper, an ultra-micro dispensing method based on the surface tension is proposed. It can realize micro size feature adhesive dispensing, here, adhesive droplet volume is in range of fL—pL. The transferring needle passes through the thin tube filled with adhesive liquid, and correspondingly, a micro amount of adhesive liquid is attached to the needle depending on the adhesion between needle and liquid. Then, the adhesive force between adhesive liquid and dispensing surface and the liquid’s self surface tension make a micro amount of adhesive liquid left on the dispensing surface and form a droplet. In this paper, we carried out a set of detailed single factor experimental study, and systematically analyzed the affection of main working parameters, including the diameter of transferring needle, dispensing speed, dispensing distance between the tip of needle and dispensing surface and the viscosity of adhesive, on dispensing results. Based on the above research results about working parameters characteristics, an ultra-micro dispensing process at fL level volume was realized. Diameter of adhesive droplet could be as small as 22.4 μm, and volume reached to 228 fL. Ultra-micro automatic continuous dispensing is realized through automatic moving path planning of transferring needle by CAD program, and we obtained two droplet dot arrays with different layouts. The proposed ultra micro dispensing system can control droplet size and dispensing position precisely. The deviation of adhesive droplet diameter is less than 2.2 μm, and the position deviation is within 1.58 μm.

Thiol-ene microfluidic chip for fast on-chip sample clean-up, separation and ESI mass spectrometry of peptides and proteins

Mass spectrometry (MS) is a key technology for sensitive and high-resolution mass analysis of peptides and proteins. Sample clean-up and chromatographic separation is typically performed prior to MS analysis to limit adduct formation and ionization suppression. Usually, this requires a high-pressure LC pump system equipped with expensive metal chromatographic columns placed in-line of an electrospray ionization (ESI) source. Microfluidic devices coupled to MS have gained considerable attention, due to the promise of low manufacturing costs, low sample consumption and channels with a high surface area to volume ratio and tailorable functional groups. Here, we describe a thiol-ene microfluidic chip capable of fast chromatographic sample clean-up, concentration, and separation of complex protein and peptide mixtures with direct on-chip ESI. On-chip reversed-phase chromatography (RPC) was performed through an in-situ polymerized monolith frit for retaining inexpensive commercially available reversed-phase (RP) spherical particles, while on-chip ESI is achieved through an emitter monolithically implemented by precision micro milling. The on-chip integration of both RPC and ESI emitter allowed for a minimization of dead-volumes and enables very fast sample clean-up, efficient ionization, and mass analysis of peptides and proteins from complex matrices.

Investigation of the specific cutting energy and its effect in shearing dominant precision micro cutting

Abstract The analysis of SCE (specific cutting energy) is vital for determining the machining efficiency. Conventionally, the machining forces are used to determine SCE, which is quantified as the energy that is consumed to remove unit volume of material. To correlate the micro-mechanics of material deformation and small-scale material removal in machining, in this research paper, the SCE has been modelled with consideration of shearing mechanism. While developing the model, small scale material indentation and deformation phenomena have been correlated with complex tool-work interaction behaviour in micro machining. The experiment was conducted for validation of the model for different light-weight materials i.e. Al alloy and Cu alloy. The investigation was done through the analysis of cutting forces and the visual examination of microchip morphology. It was found that the nonlinear increase and sharp fall of specific shearing energy (UShe) occur owing to the variations of the material removal mechanism. This is especially valid for lower values of UCT (undeformed chip thickness).