Investigation on the machinability of polycrystalline ZnSe by elliptical vibration diamond cutting.

Polycrystalline zinc selenide is widely used in advanced optical systems due to its superior optical properties. However, the soft and brittle properties bring a challenge for high-quality surface processing. In recent years, elliptical vibration cutting has been proven as a promising method for machining brittle materials. In the present research, a series of grooving and planning experiments were carried out to investigate the machinability of zinc selenide with elliptical vibration cutting. The removal mechanism was analyzed from fracture characteristics, chip morphology, and phase transformation. The results show that elliptical vibration cutting is effective in suppressing cleavage-induced craters. Reducing the nominal cutting speed is beneficial to inhibit the spring back-induced tearing of grains. A 94-time increase in the critical depth of cut was achieved by vibration trajectory optimization compared to ordinary cutting. Moreover, the influence mechanism of feed on the evolution of surface morphology was revealed. Finally, a zinc selenide microlens array was successfully fabricated. The performance was evaluated by geometric parameter measurements and a multiple imaging test. The findings provide a prospective method for ductile regime machining of zinc selenide.

Cutting depth-oriented ductile machining of infrared micro-lens arrays by elliptical vibration cutting.

Infrared micro-lens arrays (MLAs) are widely used in advanced optical systems due to their advantages such as low focusing depth and high sensitivity. Elliptical vibration cutting (EVC) is a promising approach for the fabrication of MLAs on infrared brittle materials. However, the mechanism of ductile machining of MLAs prepared by EVC has not been fully elucidated so far. In this paper, based on the vibration intermittent cutting characteristics and the transient material removal state, a ductile machining model of MLAs on brittle material by EVC was established. This model effectively calculates the subsurface damage of the machined surface and realizes the prediction of the critical depth for ductile machining of MLAs. Furthermore, the concave micro-lenses were prepared on single crystal silicon by EVC and ordinary cutting (OC) to verify this model. The results demonstrated that EVC could significantly enhance the critical depth by approximately 4.3 times compared to OC. Microstructural surface damage predominantly occurs at the exit side of the tool cutting. This proposed model accurately predicts the actual critical depth, with an average error of about 7.5%. Additionally, elevating the amplitude in the depth of cut direction could increase the critical depth, but a larger amplitude would inhibit the increase of the critical depth. This study contributes to a better understanding of ductile machining of microstructure on brittle materials and facilitates the process optimization of MLAs fabrication using EVC.

Random spherical microlens array fabricated by elliptical vibration diamond cutting and molding.

Microlens arrays (MLAs) are widely used in homogenized laser beams due to excellent optical properties. However, the interference effect generated in traditional MLA (tMLA) homogenization will reduce the quality of the homogenized spot. Hence, the random MLA (rMLA) was proposed to reduce the interference effect in the homogenization process. To achieve mass production of these high-quality optical homogenization components, the rMLA with randomness in both period and sag height was proposed first. Subsequently, MLA molds were ultra-precision machined on S316 molding steel by elliptical vibration diamond cutting. Furthermore, the rMLA components were precisely fabricated by applying molding technology. Finally, Zemax simulation and homogenization experiments were carried out to verify the advantage of the designed rMLA.

Mechanically Ultra-Robust, Elastic, Conductive, and Multifunctional Hybrid Hydrogel for a Triboelectric Nanogenerator and Flexible/Wearable Sensor.

Flexibility/wearable electronics such as strain/pressure sensors in human-machine interactions (HMI) are highly developed nowadays. However, challenges remain because of the lack of flexibility, fatigue resistance, and versatility, leading to mechanical damage to device materials during practical applications. In this work, a triple-network conductive hydrogel is fabricated by combining 2D Ti3 C2 Tx nanosheets with two kinds of 1D polymer chains, polyacrylamide, and polyvinyl alcohol. The Ti3 C2 Tx nanosheets act as the crosslinkers, which combine the two polymer chains of PAM and PVA via hydrogen bonds. Such a unique structure endows the hydrogel (MPP-hydrogel) with merits such as mechanical ultra-robust, super-elasticity, and excellent fatigue resistance. More importantly, the introduced Ti3 C2 Tx nanosheets not only enhance the hydrogel's conductivity but help form double electric layers (DELs) between the MXene nanosheets and the free water molecules inside the MPP-hydrogel. When the MPP-hydrogel is used as the electrode of the triboelectric nanogenerator (MPP-TENG), due to the dynamic balance of the DELs under the initial potential difference generated from the contact electrification as the driving force, an enhanced electrical output of the TENG is generated. Moreover, flexible strain/pressure sensors for tiny and low-frequency human motion detection are achieved. This work demonstrates a promising flexible electronic material for e-skin and HMI.

Flexible GaN-based microscale light-emitting diodes with a batch transfer by wet etching.

Flexible inorganic GaN-based microscale light-emitting diodes (µLEDs) show potential applications in wearable electronics, biomedical engineering, and human-machine interfaces. However, developing cost-effective products remains a challenge for flexible GaN-based µLEDs. Here, a facile and stable method is proposed to fabricate flexible GaN-based µLEDs from silicon substrates in an array-scale manner by wet etching. Circular and square µLED arrays with a size and pitch of 500 µm were fabricated and then transferred to a flexible acrylic/copper substrate. The as-fabricated flexible µLEDs can maintain their structure intact while exhibiting a significant increase in external quantum efficiency. This Letter promotes the application of simple and low-cost flexible µLED devices, especially for virtual displays, wearables, and curvilinear displays.

Lucas-Washburn Equation-Based Modeling of Capillary-Driven Flow in Porous Systems.

Fluid flow in porous systems driven by capillary pressure is one of the most ubiquitous phenomena in nature and industry, including petroleum and hydraulic engineering as well as material and life sciences. The classical Lucas-Washburn (LW) equation and its modified forms were developed and have been applied extensively to elucidate the fundamental mechanisms underlying the basic statics and dynamics of the capillary-driven flow in porous systems. The LW equation assumes that fluids are incompressible Newton ones and that capillary channels all have the same radii. This kind of hypothesis is not true for many natural situations, however, where porous systems comprise complicated pore and capillary channel structures at microscales. The LW equation therefore often leads to inaccurate capillary imbibition predictions in such situations. Numerous studies have been conducted in recent years to develop and assess the modifications and extensions of the LW equation in various porous systems. Significant progresses in computational techniques have also been attained to further improve our understanding of imbibition dynamics. A state-of-the-art review is therefore needed to summarize the recent significant models and numerical simulation techniques as well as to discuss key ongoing research topics arising from various new engineering practices. The theoretical basis of the LW equation is first introduced in this review and recent progress in mathematical models is then summarized to demonstrate the modifications and extensions of this equation to various microchannels and porous media. These include capillary tubes with nonuniform and noncircular cross sections, discrete fractures, and capillary tubes that are not straight as well as heterogeneous porous media. Numerical studies on the LW equation are also reviewed, and comments on future works and research directions for LW-based capillary-driven flows in porous systems are listed.

Tunable fabrication of concave microlens arrays by initiative cooling-based water droplet condensation.

Microlens arrays (MLAs), as one of the key features in the optoelectronics field, have attracted a lot of attention recently. Unfortunately, existing fabrication methods of MLAs have many disadvantages, such as complex fabrication procedures and difficult morphology control. This paper presents a low-cost and tunable fabrication approach for concave MLAs on ultraviolet (UV) polymer surfaces. We used condensed water droplets, formed by initiative cooling, as the template for the formation of concave MLAs in this approach. A sacrificial layer of polymer material was introduced to fabricate concave MLAs with different morphology parameters. The three most important parameters of MLAs, i.e. diameter, cross-sectional profile, and packing distance, can be tuned by the proposed novel fabrication approach. By controlling the condensation time of water droplets, we can control the diameter of the concave MLAs. Moreover, the cross-sectional profile can be controlled by replacing the sacrificial layer material to change the interaction among the water droplets, sacrificial polymers, and UV polymers. In addition, the packing distance of the MLAs can also be adjusted by introducing the lateral flow of the sacrificial polymer, which was driven by the additional sacrificial polymer dispensed on the substrate. Furthermore, the UV polymer film with MLAs on its surface was applied for the packaging of high power green LEDs. Consequently, the optical output power of green LED modules is enhanced by 11.4% when using the MLAs at the driving current of 500 mA.

Novel functional fiber loaded with carbon dots for the deep removal of Cr(VI) by adsorption and photocatalytic reduction.

A novel functional fiber (PAN-CDs) loaded with carbon dots (CDs) with excellent photoreduction and adsorption properties for Cr(VI) was prepared via an amidization reaction between the CDs' carboxyl groups and amine groups on polyacrylonitrile (PAN)-based ion exchange fibers, which could completely preserve the fluorescence properties of the CDs. The photoluminescence (PL), photocatalysis and adsorption properties of PAN-CDs were characterized and analyzed. The PAN-CDs possess high adsorption capacity (297.6 mg/g) and excellent kinetic behavior (attaining adsorption equilibrium in 30 min) for Cr(VI) adsorption. Furthermore, the residual Cr(VI) (approximately 3 mg/L) after adsorption could be removed completely by subsequent photoreduction by the PAN-CDs. The Cr-saturated PAN-CDs could be easily separated by filtering and regenerated, with no observable decay of removal efficiency after five regeneration cycles. In addition, due to the PL quenching action of Cr(VI), the PAN-CDs can also be used as sensor for quantitative detection of trace Cr(VI) in aqueous solution.

Hierarchical metal/polymer metamaterials of tunable negative Poisson's ratio fabricated by initiator-integrated 3D printing (i3DP).

Metamaterials with artificially designed architectures can achieve unique and even unprecedented physical properties, which show promising applications in actuators, amplifiers and micromechanical controls. An initiator-integrated 3D printing technology (i3DP) was applied in this study to create scalable, metal/polymer meta-mechanical materials, which can gradually achieve negative Poisson's ratio, high strength and ultralow density, as well as high compressive and super-elastic behavior. The i3DP was enabled by integrating an atomic-transfer radical polymerization (ATRP) initiator with UV-curable resin, followed by polyelectrolyte brushes (PMETAC) grafting via surface-initiated ATRP and thereafter electroless plating to form metal coatings. Compared with polymer structures, the compressive stress of metal-polymer structure can be doubled when deposited with a 190 nm copper layer. The hollow metallic materials possess a tunable Poisson's ratio, and the highest average recoverability, which can recover nearly completely to their original shape after over 30% compression. Overall, this i3DP approach provides meta-structures with substantial benefits from the hierarchical design and fabrication flexibility.

Development of ultralight, super-elastic, hierarchical metallic meta-structures with i3DP technology.

Lightweight and mechanically robust materials show promising applications in thermal insulation, energy absorption, and battery catalyst supports. This study demonstrates an effective method for creation of ultralight metallic structures based on initiator-integrated 3D printing technology (i3DP), which provides a possible platform to design the materials with the best geometric parameters and desired mechanical performance. In this study, ultralight Ni foams with 3D interconnected hollow tubes were fabricated, consisting of hierarchical features spanning three scale orders ranging from submicron to centimeter. The resultant materials can achieve an ultralight density of as low as 5.1 mg cm-3 and nearly recover after significant compression up to 50%. Due to a high compression ratio, the hierarchical structure exhibits superior properties in terms of energy absorption and mechanical efficiency. The relationship of structural parameters and mechanical response was established. The ability of achieving ultralight density <10 mg cm-3 and the stable [Formula: see text] scaling through all range of relative density, indicates an advantage over the previous stochastic metal foams. Overall, this initiator-integrated 3D printing approach provides metallic structures with substantial benefits from the hierarchical design and fabrication flexibility to ultralight applications.

Radiomic Analysis of Contrast-Enhanced CT Predicts Glypican 3-Positive Hepatocellular Carcinoma.

BACKGROUND: The Glypican 3 (GPC3)-positive expression in Hepatocellular Carcinoma (HCC) is associated with a worse prognosis. Moreover, GPC3 has emerged as an immunotherapeutic target in advanced unresectable HCC systemic therapy. It is significant to diagnose GPC3-positive HCCs before therapy. Regarding imaging diagnosis of HCC, dynamic contrast-enhanced CT is more common than MRI in many regions. OBJECTIVE: The aim of this study was to construct and validate a radiomics model based on contrast-enhanced CT to predict the GPC3 expression in hepatocellular carcinoma. METHODS: This retrospective study included 141 (training cohort: n = 100; validation cohort: n = 41) pathologically confirmed HCC patients. Radiomics features were extracted from the Artery Phase (AP) images of contrast-enhanced CT. Logistic regression with the Least Absolute Shrinkage and Selection Operator (LASSO) regularization was used to select features to construct radiomics score (Rad-score). A final combined model, including the Rad-score of the selected features and clinical risk factors, was established. Receiver Operating Characteristic (ROC) curve analysis, Delong test, and Decision Curve Analysis (DCA) were used to assess the predictive performance of the clinical and radiomics models. RESULTS: 5 features were selected to construct the AP radiomics model of contrast-enhanced CT. The radiomics model of AP from contrast-enhanced CT was superior to the clinical model of AFP in training cohorts (P < 0.001), but not superior to the clinical model in validation cohorts (P = 0.151). The combined model (AUC = 0.867 vs. 0.895), including AP Rad-score and serum Alpha-Fetoprotein (AFP) levels, improved the predictive performance more than the AFP model (AUC = 0.651 vs. 0.718) in the training and validation cohorts. The combined model, with a higher decision curve indicating more net benefit, exhibited a better predictive performance than the AP radiomics model. DCA revealed that at a range threshold probability approximately above 60%, the combined model added more net benefit compared to the AP radiomics model of contrastenhanced CT. CONCLUSION: A combined model including AP Rad-score and serum AFP levels based on contrast-enhanced CT could preoperatively predict GPC3-positive expression in HCC.

Enzyme Immobilization by Inkjet Printing on Reagentless Biosensors for Electrochemical Phosphate Detection.

Enzyme-based biosensors commonly utilize the drop-casting method for their surface modification. However, the drawbacks of this technique, such as low reproducibility, coffee ring effects, and challenges in mass production, hinder its application. To overcome these limitations, we propose a novel surface functionalization strategy of enzyme crosslinking via inkjet printing for reagentless enzyme-based biosensors. This method includes printing three functional layers onto a screen-printed electrode: the enzyme layer, crosslinking layer, and protective layer. Nanomaterials and substrates are preloaded together during our inkjet printing. Inkjet-printed electrodes feature a uniform enzyme deposition, ensuring high reproducibility and superior electrochemical performance compared to traditional drop-casted ones. The resultant biosensors display high sensitivity, as well as a broad linear response in the physiological range of the serum phosphate. This enzyme crosslinking method has the potential to extend into various enzyme-based biosensors through altering functional layer components.

Inverse kinematics solution and control method of 6-degree-of-freedom manipulator based on deep reinforcement learning.

The advent of Industry 4.0 has significantly promoted the field of intelligent manufacturing, which is facilitated by the development of new technologies are emerging. Robot technology and robot intelligence methods have rapidly developed and been widely applied. Manipulators are widely used in industry, and their control is a crucial research topic. The inverse kinematics solution of manipulators is an important part of manipulator control, which calculates the joint angles required for the end effector to reach a desired position and posture. Traditional inverse kinematics solution algorithms often face the problem of insufficient generalization, and iterative methods have challenges such as large computation and long solution time. This paper proposes a reinforcement learning-based inverse kinematics solution algorithm, called the MAPPO-IK algorithm. The algorithm trains the manipulator agent using the MAPPO algorithm and calculates the difference between the end effector state of the manipulator and the target posture in real-time by designing a reward mechanism, while considering Gaussian distance and cosine distance. Through experimental comparative analysis, the feasibility, computational efficiency, and superiority of this reinforcement learning algorithm are verified. Compared with traditional inverse kinematics solution algorithms, this method has good generalization and supports real-time computation, and the obtained result is a unique solution. Reinforcement learning algorithms have better adaptability to complex environments and can handle different sudden situations in different environments. This algorithm also has the advantages of path planning, intelligent obstacle avoidance, and other advantages in dynamically processing complex environmental scenes.

Fabrication of Large-Area Silicon Spherical Microlens Arrays by Thermal Reflow and ICP Etching.

In this paper, we proposed an efficient and high-precision process for fabricating large-area microlens arrays using thermal reflow combined with ICP etching. When the temperature rises above the glass transition temperature, the polymer cylinder will reflow into a smooth hemisphere due to the surface tension effect. The dimensional differences generated after reflow can be corrected using etching selectivity in the following ICP etching process, which transfers the microstructure on the photoresist to the substrate. The volume variation before and after reflow, as well as the effect of etching selectivity using process parameters, such as RF power and gas flow, were explored. Due to the surface tension effect and the simultaneous molding of all microlens units, machining a 3.84 × 3.84 mm2 silicon microlens array required only 3 min of reflow and 15 min of ICP etching with an extremely low average surface roughness Sa of 1.2 nm.

Effects of Dietary Supplementation of Stimbiotics to Sows on Lactation Performance, Immune Function, and Anti-Inflammatory and Antioxidant Capacities during Late Gestation and Lactation.

Stimbiotic supplementation may provide an innovative feed additive solution to accelerate the proliferation of beneficial fiber-degrading bacteria in the distal intestine and the utilization of dietary fiber. Optimal utilization of dietary fiber has multiple benefits for gut health and nutrient utilization. This study was conducted to evaluate the late gestation and lactation performance, the plasma, colostrum, and milk immunoglobulin (IgA, IgG, and IgM) concentrations, and the anti-inflammatory and antioxidant biomarkers in plasma of sows fed with or without a stimbiotic during the late gestation and lactation phase. A total of 40 sows were allocated to two treatment groups: control (CT) with no supplementation or 100 mg/kg stimbiotic (VP), with 20 sows per treatment. Sows were fed the treatment diets from d 85 of gestation to d 28 of lactation. In the results, the average daily weight gain of piglets during lactation was greater from sows fed in the VP group compared to that in the CT group (p < 0.05). The plasma concentrations of IgM at farrowing and IgG at weaning of the sows fed the diet with the stimbiotic supplementation were much higher than those in the CT sows (p < 0.05), respectively. In addition, the dietary stimbiotic increased the concentrations of IgM in the colostrum and of IgA and IgM in the milk at d 14 of lactation (p < 0.05). Plasma concentrations of malondialdehyde (MDA) on d 0 and d 28 of lactation tended to be lower in sows fed the VP diets compared with those of the sows fed the CT diets. Thus, our study indicated that stimbiotic supplementation could improve the daily weight gain of piglets and the immune function of sows in lactation.

Inductively Coupled Plasma Dry Etching of Silicon Deep Trenches with Extremely Vertical Smooth Sidewalls Used in Micro-Optical Gyroscopes.

Micro-optical gyroscopes (MOGs) place a range of components of the fiber-optic gyroscope (FOG) onto a silicon substrate, enabling miniaturization, low cost, and batch processing. MOGs require high-precision waveguide trenches fabricated on silicon instead of the ultra-long interference ring of conventional F OGs. In our study, the Bosch process, pseudo-Bosch process, and cryogenic etching process were investigated to fabricate silicon deep trenches with vertical and smooth sidewalls. Different process parameters and mask layer materials were explored for their effect on etching. The effect of charges in the Al mask layer was found to cause undercut below the mask, which can be suppressed by selecting proper mask materials such as SiO2. Finally, ultra-long spiral trenches with a depth of 18.1 µm, a verticality of 89.23°, and an average roughness of trench sidewalls less than 3 nm were obtained using a cryogenic process at -100 °C.

Laminaria japonica Polysaccharides Improves the Growth Performance and Faecal Digestive Enzyme Activity of Weaned Piglets.

The aim of this experiment was to investigate the effect of Laminaria japonica polysaccharide (LJP) supplementation at levels of 100, 200, or 400 mg/kg on the growth performance, faecal digestive enzyme activity, and serum biochemistry and amino acids of weaned piglets. One hundred and twenty weaned piglets (Barkshire × Licha Black, 21 days old, 6.13 ± 0.16 kg) were randomly divided into four groups with five replicates of six piglets in each group based on body weight. Piglets were fed with different levels (0, 100, 200, and 400 mg/kg) of LJP for a 21-day trial. On day 21, faecal and blood samples were collected from one piglet per pen. The results showed that the supplementation of the 200 and 400 mg/kg LJP significantly increased average daily gain (ADG) and average daily feed intake (ADFI) compared to the control group (p = 0.007; p = 0.002), and dietary LJP linearly increased ADG and ADFI (p = 0.002; p < 0.001). In addition, the supplementation of the 200 and 400 mg/kg LJP significantly increased faecal amylase activity (p < 0.001) compared to the control group, and dietary LJP linearly increased faecal amylase and lipase activities (p = 0.001; p = 0.037). Moreover, dietary LJP at 400 mg/kg increased serum histidine content compared to the other groups (p = 0.002), and dietary LJP linearly increased the contents of serum histidine and asparagine in piglets (p < 0.001; p = 0.046). In conclusion, supplementation of 200 and 400 mg/kg LJP could enhance growth performance and faecal digestive enzyme activity and modulate the serum amino acid content of weaned piglets, potentially contributing to the health of weaned piglets.

Fabrication of polymer micro-lens array with pneumatically diaphragm-driven drop-on-demand inkjet technology.

The paper reports an effective method to fabricate micro-lens arrays with the ultraviolet-curable polymer, using an original pneumatically diaphragm-driven drop-on-demand inkjet system. An array of plano convex micro-lenses can be formed on the glass substrate due to surface tension and hydrophobic effect. The micro-lens arrays have uniform focusing function, smooth and real planar surface. The fabrication process showed good repeatability as well, fifty micro-lenses randomly selected form 9 × 9 miro-lens array with an average diameter of 333.28µm showed 1.1% variations. Also, the focal length, the surface roughness and optical property of the fabricated micro-lenses are measured, analyzed and proved satisfactory. The technique shows great potential for fabricating polymer micro-lens arrays with high flexibility, simple technological process and low production cost.

Source-like solution for radial imbibition into a homogeneous semi-infinite porous medium.

We describe the imbibition process from a point source into a homogeneous semi-infinite porous material. When body forces are negligible, the advance of the wetting front is driven by capillary pressure and resisted by viscous forces. With the assumption that the wetting front assumes a hemispherical shape, our analytical results show that the absorbed volume flow rate is approximately constant with respect to time, and that the radius of the wetting evolves in time as r ≈ t(1/3). This cube-root law for the long-time dynamics is confirmed by experiments using a packed cell of glass microspheres with average diameter of 42 µm. This result complements the classical one-dimensional imbibition result where the imbibition length l ≈ t(1/2), and studies in axisymmetric porous cones with small opening angles where l ≈ t(1/4) at long times.

Fabrication of High Precision Silicon Spherical Microlens Arrays by Hot Embossing Process.

In this paper, a high-precision, low-cost, batch processing nanoimprint method is proposed to process a spherical microlens array (MLA). The nanoimprint mold with high surface precision and low surface roughness was fabricated by single-point diamond turning. The anti-sticking treatment of the mold was carried out by perfluorooctyl phosphoric acid (PFOPA) liquid deposition. Through the orthogonal experiment of hot embossing with the treated mold and subsequent inductively coupled plasma (ICP) etching, the microstructure of MLA was transferred to the silicon substrate, with a root mean square error of 17.7 nm and a roughness of 12.1 nm Sa. The average fitted radius of the microlens array units is 406.145 µm, which is 1.54% different from the design radius.