Multiscale 3D printing via active nozzle size and shape control.

Three-dimensional (3D) printers extruding filaments through a fixed nozzle encounter a conflict between high resolution, requiring small diameters, and high speed, requiring large diameters. This limitation is especially pronounced in multiscale architectures featuring both bulk and intricate elements. Here, we introduce adaptive nozzle 3D printing (AN3DP), a technique enabling dynamic alteration of nozzle diameter and cross-sectional shape during printing. The AN3DP nozzle consists of eight independently controllable, tendon-driven pins arrayed around a flexible, pressure-resistant membrane. The design incorporates a tapered angle optimized for extruding shear-thinning inks and a pointed tip suitable for constrained-space printing, such as conformal and embedded printing. AN3DP's efficacy is demonstrated through the fabrication of components with continuous gradients, eliminating the need for discretization, and achieving enhanced density and contour precision compared to traditional 3D printing methods. This platform substantially expands the scope of extrusion-based 3D printers, thus facilitating diverse applications, including bioprinting cell-laden and hierarchical implants with bone-like microarchitecture.

Enhanced Photocatalytic Degradation Activity Using the V2O5/RGO Composite.

Semiconductor-based photocatalyst materials played an important role in the degradation of organic compounds in recent years. Photocatalysis is a simple, cost-effective, and environmentally friendly process for degrading organic compounds. In this work, vanadium pentoxide (V2O5) and V2O5/RGO (reduced graphene oxide) composite were synthesized by a hydrothermal method. The prepared samples were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), Raman spectroscopy, and UV-Vis spectroscopic analysis, etc. Raman analysis shows the occurrence of RGO characteristic peaks in the composite and different vibrational modes of V2O5. The band gap of flake-shaped V2O5 is reduced and its light absorption capacity is enhanced by making its composite with RGO. The photocatalytic degradation of methylene blue (MB) was studied using both V2O5 and V2O5/RGO composite photocatalyst materials. The V2O5/RGO composite exhibits a superior photocatalytic performance to V2O5. Both catalyst and light play an important role in the degradation process.

High-Fidelity Cytosine Base Editing in a GC-Rich Corynebacterium glutamicum with Reduced DNA Off-Target Editing Effects.

Genome editing technology is a powerful tool for programming microbial cell factories. However, rat APOBEC1-derived cytosine base editor (CBE) that converts C•G to T•A at target genes induced DNA off-targets, regardless of single-guide RNA (sgRNA) sequences. Although the high efficiencies of the bacterial CBEs have been developed, a risk of unidentified off-targets impeded genome editing for microbial cell factories. To address the issues, we demonstrate the genome engineering of Corynebacterium glutamicum as a GC-rich model industrial bacterium by generating premature termination codons (PTCs) in desired genes using high-fidelity cytosine base editors (CBEs). Through this CBE-STOP approach of introducing specific cytosine conversions, we constructed several single-gene-inactivated strains for three genes (ldh, idsA, and pyc) with high base editing efficiencies of average 95.6% (n = 45, C6 position) and the highest success rate of up to 100% for PTCs and ultimately developed a strain with five genes (ldh, actA, ackA, pqo, and pta) that were inactivated sequentially for enhancing succinate production. Although these mutant strains showed the desired phenotypes, whole-genome sequencing (WGS) data revealed that genome-wide point mutations occurred in each strain and further accumulated according to the duration of CBE plasmids. To lower the undesirable mutations, high-fidelity CBEs (pCoryne-YE1-BE3 and pCoryne-BE3-R132E) was employed for single or multiplexed genome editing in C. glutamicum, resulting in drastically reduced sgRNA-independent off-targets. Thus, we provide a CRISPR-assisted bacterial genome engineering tool with an average high efficiency of 90.5% (n = 76, C5 or C6 position) at the desired targets. IMPORTANCE Rat APOBEC1-derived cytosine base editor (CBE) that converts C•G to T•A at target genes induced DNA off-targets, regardless of single-guide RNA (sgRNA) sequences. Although the high efficiencies of bacterial CBEs have been developed, a risk of unidentified off-targets impeded genome editing for microbial cell factories. To address the issues, we identified the DNA off-targets for single and multiple genome engineering of the industrial bacterium Corynebacterium glutamicum using whole-genome sequencing. Further, we developed the high-fidelity (HF)-CBE with significantly reduced off-targets with comparable efficiency and precision. We believe that our DNA off-target analysis and the HF-CBE can promote CRISPR-assisted genome engineering over conventional gene manipulation tools by providing a markerless genetic tool without need for a foreign DNA donor.

Sulfur Nanoparticle-Decorated Nickel Cobalt Sulfide Hetero-Nanostructures with Enhanced Energy Storage for High-Performance Supercapacitors.

Transition-metal sulfides exaggerate higher theoretical capacities and were considered a type of prospective nanomaterials for energy storage; their inherent weaker conductivities and lower electrochemical active sites limited the commercial applications of the electrodes. The sheet-like nickel cobalt sulfide nanoparticles with richer sulfur vacancies were fabricated by a two-step hydrothermal technique. The sheet-like nanoparticles self-combination by ultrathin nanoparticles brought active electrodes entirely contacted with the electrolytes, benefiting ion diffusion and charges/discharges. Nevertheless, defect engineers of sulfur vacancy at the atomic level raise the intrinsic conductivities and improve the active sites for energy storage functions. As a result, the gained sulfur-deficient NiCo2S4 nanosheets consist of good specific capacitances of 971 F g-1 at 2 A g-1 and an excellent cycle span, retaining 88.7% of the initial capacitance over 3500 cyclings. Moreover, the values of capacitance results exhibited that the fulfilling characteristic of the sample was a combination of the hydrothermal procedure and the surface capacitances behavior. This novel investigation proposes a new perspective to importantly improve the electrochemical performances of the electrode by the absolute engineering of defects and morphologies in the supercapacitor field.

Crosslinking effect of borax additive on the thermal properties of polymer-based 1D and 2D nanocomposites used as thermal interface materials.

Recently, polymer-based materials have been used in various filed of applications, but their low thermal conductivity restricts their uses due to the high interfacial thermal resistance. Therefore, in this study, one-dimensional thin-walled carbon nanotube (1D-TWCNT) and two-dimensional boron nitride nanosheet (2D-BNNS) fillers were used to enhance the thermal properties of polyvinyl alcohol (PVA). An important factor to be considered in enhancing the thermal properties of PVA is the interfacial configuration strategy, which provides sufficient pathways for phonon transport and the controlled loss of the intrinsic thermal properties of the filler nanomaterial. In this study, the effect of sodium tetraborate (borax) additive on the thermal properties of 1D-TWCNT/PVA and 2D-BNNS/PVA nanocomposites was explored. Borax is a well-known crosslinking additive that can be used with PVA. The crosslink density of the PVA-borax nanocomposite was controlled by changing its borate ion concentration. The addition of borax into nanocomposites improves the conductivity of 1D-TWCNT/PVA nanocomposites up to 14.5% (4 wt.% borax) and of 2D-BNNS/PVA nanocomposite up to 30.6% for BNNS (2 wt.% borax). Thus, when borax was added, the 2D-BNNS/PVA nanocomposite showed better results than the 1D-TWCNT/PVA nanocomposite.

Chemically Synthesized Iron-Oxide-Based Pure Negative Electrode for Solid-State Asymmetric Supercapacitor Devices.

Among energy storage devices, supercapacitors have received considerable attention in recent years owing to their high-power density and extended cycle life. Researchers are currently making efforts to improve energy density using different asymmetric cell configurations, which may provide a wider potential window. Many studies have been conducted on positive electrodes for asymmetric supercapacitor devices; however, studies on negative electrodes have been limited. In this study, iron oxides with different morphologies were synthesized at various deposition temperatures using a simple chemical bath deposition method. A nanosphere-like morphology was obtained for α-Fe2O3. The obtained specific capacitance (Cs) of α-Fe2O3 was 2021 F/g at a current density of 4 A/g. The negative electrode showed an excellent capacitance retention of 96% over 5000 CV cycles. The fabricated asymmetric solid-state supercapacitor device based on α-Fe2O3-NF//Co3O4-NF exhibited a Cs of 155 F/g and an energy density of 21 Wh/kg at 4 A/g.

Photocatalytic degradation of tetracycline antibiotics using hydrothermally synthesized two-dimensional molybdenum disulfide/titanium dioxide composites.

Tetracycline (TC) is a persistent antibiotic used in many countries, including China, India, and the United States of America (USA), because of its low price and effectiveness in enhancing livestock production. However, such antibiotics can have toxic effects on living organisms via complexation with metals, and their accumulation leading to teratogenicity and carcinogenicity. In this study, two-dimensional molybdenum disulfide/titanium dioxide (MoS2/TiO2) composites with different amounts of molybdenum disulfide (MoS2) were prepared via a simple, cost-effective, and pollution-free hydrothermal route. The synthesized MoS2/TiO2 microstructures were thoroughly characterized and their performance for the photocatalytic degradation of antibiotics such as TC was investigated. In the degradation experiments, the photocatalytic activities of TiO2 and the MoS2/TiO2 composites were compared, and the effects of different parameters, such as catalyst dose and electrolyte solution pH, were investigated. Under irradiation, the MoS2/TiO2 composites possessed superior photodegradation activity toward TC because of their excellent adsorption abilities, suitable band positions, and large surface areas as well as the effective charge-transfer ability of MoS2. Kinetics studies revealed that the photocatalytic degradation process followed pseudo-first-order reaction kinetics. In addition, a degradation mechanism for TC was proposed.

Nanoflakes-like nickel cobaltite as active electrode material for 4-nitrophenol reduction and supercapacitor applications.

Catalytic reduction of nitroaromatic compounds present in wastewater by nanostructured materials is a promising process for wastewater treatment. A multifunctional electrode based on ternary spinal nickel cobalt oxide is used in the catalytic reduction of a nitroaromatic compound and supercapacitor application. In this study, we designed nanoflakes- like nickel cobaltite (NiCo2O4) using a simple, chemical, cost-effective hydrothermal method. Nanoflakes- like NiCo2O4 samples are tested as catalysts toward rapid reduction of 4-nitrophenol and as electrode materials for supercapacitors. The conversion of 4-nitrophenol into 4-aminophenol is achieved using a reducing agents like sodium borohydride and NiCo2O4 catalyst. Effect of catalyst loading, 4-nitrophenol and sodium borohydride concentrations on the catalytic performance of 4-nitrophenol is studied. As sodium borohydride concentration increases the catalytic efficiency of 4-nitrophenol increased due to more BH4- ions available which provides more electrons for catalytic reduction of 4-nitrophenol. Catalytic reduction of 4-nitrophenol using sodium borohydride as a reducing agent was based on the Langmuir-Hinshelwood mechanism. This mechanism follows the apparent pseudo first order reaction kinetics. Additionally, NiCo2O4 electrode is used for energy storage application. The nanoflakes-like NiCo2O4 electrode deposited at 120 °C shows a higher specific capacitance than samples synthesized at 100 and 140 °C. The maximum specific capacitance observed for NiCo2O4 electrode is 1505 Fg-1 at a scan rate of 5 mV s-1 with high stability of 95% for 5000 CV cycles.

Mechanically Sustainable Starch-Based Flame-Retardant Coatings on Polyurethane Foams.

The use of halogen-based materials has been regulated since toxic substances are released during combustion. In this study, polyurethane foam was coated with cationic starch (CS) and montmorillonite (MMT) nano-clay using a spray-assisted layer-by-layer (LbL) assembly to develop an eco-friendly, high-performance flame-retardant coating agent. The thickness of the CS/MMT coating layer was confirmed to have increased uniformly as the layers were stacked. Likewise, a cone calorimetry test confirmed that the heat release rate and total heat release of the coated foam decreased by about 1/2, and a flame test showed improved fire retardancy based on the analysis of combustion speed, flame size, and residues of the LbL-coated foam. More importantly, an additional cone calorimeter test was performed after conducting more than 1000 compressions to assess the durability of the flame-retardant coating layer when applied in real life, confirming the durability of the LbL coating by the lasting flame retardancy.

Ultrasound assisted synthesis of highly active nanoflower-like CoMoS4 electrocatalyst for oxygen and hydrogen evolution reactions.

Rapid technological development requires sustainable, pure, and clean energy systems, such as hydrogen energy. It is difficult to fabricate efficient, highly active, and inexpensive electrocatalysts for the overall water splitting reaction: the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). The present research work deals with a simple hydrothermal synthesis route assisted with ultrasound that was used to fabricate a 3D nanoflower-like porous CoMoS4 electrocatalyst. A symmetric electrolyzer cell was fabricated using a CoMoS4 electrode as both the anode and cathode, with a cell voltage of 1.51 V, to obtain a current density of 10 mA/cm2. Low overpotentials were observed for the CoMoS4 electrode (250 mV for OER and 141 mV for HER) at a current density of 10 mA/cm2.

Three-dimensional nanoflower-like hierarchical array of multifunctional copper cobaltate electrode as efficient electrocatalyst for oxygen evolution reaction and energy storage application.

The study deals with the hydrothermal growth of a CuCo2O4 hierarchical 3D nanoflower-like array on carbon cloth (CuCo2O4@CC), which is a useful multifunctional electrode. The electrocatalytic oxygen evolution reaction (OER) study of the CuCo2O4@CC electrode shows high durability and good activity in 1 M KOH. As an energy storage electrode, it shows a high specific capacitance of 1438 Fg-1 at 10 mA cm-2 in a 3 M KOH electrolyte. The electrochemical stability of the CuCo2O4@CC electrode was tested for 5000 cycles at 10 mA cm-2, and it showed 98.6% stability. This CuCo2O4@CC electrode produces a capacitance of 10 mA cm-2 at an overpotential of 288 mV for the OER, with a Tafel slope of 64.2 mV dev-1. The electrochemical stability measured at an overpotential of 292 mV for 12 h at 10 mA cm-2 shows good electronic stability in an alkaline medium. The enhanced electrochemical performance of the CuCo2O4@CC electrode may be due to the Cu and Co counterparts in addition to the high surface area. The CuCo2O4@CC electrode is a simple, flexible, and cost-effectivive electrode in both electrocatalytic OER and energy storage applications.

Topology Optimization of Planar Gear-Linkage Mechanisms.

Topology optimization for mechanism synthesis has been developed for the simultaneous determination of the number and dimension of mechanisms. However, these methods can be used to synthesize linkage mechanisms that consist only of links and joints because other types of mechanical elements such as gears cannot be simultaneously synthesized. In this study, we aim to develop a gradient-based topology optimization method which can be used to synthesize mechanisms consisting of both linkages and gears. For the synthesis, we propose a new ground model defined by two superposed design spaces: the linkage and gear design spaces. The gear design space is discretized by newly proposed gear blocks, each of which is assumed to rotate as an output gear, while the linkage design space is discretized by zero-length-spring-connected rigid blocks. Another set of zero-length springs is introduced to connect gear blocks to rigid blocks, and their stiffness values are varied to determine the existence of gears when they are necessary to produce the desired path. After the proposed topology-optimization-based synthesis formulation and its numerical implementation are presented, its effectiveness and validity are checked with various synthesis examples involving gear-linkage and linkage-only mechanisms.

Design and Electro-Thermo-Mechanical Behavior Analysis of Au/Si3N4 Bimorph Microcantilevers for Static Mode Sensing.

This paper presents a design optimization method based on theoretical analysis and numerical calculations, using a commercial multi-physics solver (e.g., ANSYS and ESI CFD-ACE+), for a 3D continuous model, to analyze the bending characteristics of an electrically heated bimorph microcantilever. The results from the theoretical calculation and numerical analysis are compared with those measured using a CCD camera and magnification lenses for a chip level microcantilever array fabricated in this study. The bimorph microcantilevers are thermally actuated by joule heating generated by a 0.4 µm thin-film Au heater deposited on 0.6 µm Si3N4 microcantilevers. The initial deflections caused by residual stress resulting from the thermal bonding of two metallic layers with different coefficients of thermal expansion (CTEs) are additionally considered, to find the exact deflected position. The numerically calculated total deflections caused by electrical actuation show differences of 10%, on average, with experimental measurements in the operating current region (i.e., ~25 mA) to prevent deterioration by overheating. Bimorph microcantilevers are promising components for use in various MEMS (Micro-Electro-Mechanical System) sensing applications, and their deflection characteristics in static mode sensing are essential for detecting changes in thermal stress on the surface of microcantilevers.

Inhibition of senescence and promotion of the proliferation of chondrocytes from articular cartilage by CsA and FK506 involves inhibition of p38MAPK.

Cyclosporine A (CsA) and tacrolimus (FK506) are the most important immunosuppressive compounds that block the activation of helper T-cells. In this study, we investigated the effects of CsA and FK506 on growth and senescence of articular chondrocytes. Chondrocytes from young rabbit cartilage entered senescence after 8.6 ± 0.8 population doublings (PDs), while chondrocytes treated with CsA and FK506 entered senescence after 12.3 ± 1.4 and 13.7 ± 0.6 PDs, respectively. Furthermore, chondrocytes from the cartilage of old rabbits were senescent after 2.6 ± 0.9 PDs, whereas those treated with CsA and FK506 were senescent after 8.2 ± 1.8 and 6.9 ± 1.6 PDs, respectively. These compounds also inhibited senescence induction of chondrocytes in a high-cell density pellet culture system. We previously reported that p38MAPK plays a critical role in the onset of senescence in chondrocyte. This study revealed that the phosphorylation of p38MAPK was inhibited by either CsA or FK506. The early onset of senescence in chondrocyte harboring MKK6E, which is a constitutively-active form of MKK6 and increases p38MAPK phosphorylation, was blocked by CsA. These results suggest that CsA and FK506 increase the proliferation and inhibit the senescence of articular chondrocytes through inactivation of p38MAPK.

Vehicle Position Estimation Based on Magnetic Markers: Enhanced Accuracy by Compensation of Time Delays.

The real-time recognition of absolute (or relative) position and orientation on a network of roads is a core technology for fully automated or driving-assisted vehicles. This paper presents an empirical investigation of the design, implementation, and evaluation of a self-positioning system based on a magnetic marker reference sensing method for an autonomous vehicle. Specifically, the estimation accuracy of the magnetic sensing ruler (MSR) in the up-to-date estimation of the actual position was successfully enhanced by compensating for time delays in signal processing when detecting the vertical magnetic field (VMF) in an array of signals. In this study, the signal processing scheme was developed to minimize the effects of the distortion of measured signals when estimating the relative positional information based on magnetic signals obtained using the MSR. In other words, the center point in a 2D magnetic field contour plot corresponding to the actual position of magnetic markers was estimated by tracking the errors between pre-defined reference models and measured magnetic signals. The algorithm proposed in this study was validated by experimental measurements using a test vehicle on a pilot network of roads. From the results, the positioning error was found to be less than 0.04 m on average in an operational test.

Numerical Modeling and Experimental Validation by Calorimetric Detection of Energetic Materials Using Thermal Bimorph Microcantilever Array: A Case Study on Sensing Vapors of Volatile Organic Compounds (VOCs).

Bi-layer (Au-Si3N4) microcantilevers fabricated in an array were used to detect vapors of energetic materials such as explosives under ambient conditions. The changes in the bending response of each thermal bimorph (i.e., microcantilever) with changes in actuation currents were experimentally monitored by measuring the angle of the reflected ray from a laser source used to illuminate the gold nanocoating on the surface of silicon nitride microcantilevers in the absence and presence of a designated combustible species. Experiments were performed to determine the signature response of this nano-calorimeter platform for each explosive material considered for this study. Numerical modeling was performed to predict the bending response of the microcantilevers for various explosive materials, species concentrations, and actuation currents. The experimental validation of the numerical predictions demonstrated that in the presence of different explosive or combustible materials, the microcantilevers exhibited unique trends in their bending responses with increasing values of the actuation current.

Development of an integrated sensor module for a non-invasive respiratory monitoring system.

A respiratory monitoring system has been developed for analyzing the carbon dioxide (CO2) and oxygen (O2) concentrations in the expired air using gas sensors. The data can be used to estimate some medical conditions, including diffusion capability of the lung membrane, oxygen uptake, and carbon dioxide output. For this purpose, a 3-way valve derived from a servomotor was developed, which operates synchronously with human respiratory signals. In particular, the breath analysis system includes an integrated sensor module for valve control, data acquisition through the O2 and CO2 sensors, and respiratory rate monitoring, as well as software dedicated to analysis of respiratory gasses. In addition, an approximation technique for experimental data based on Haar-wavelet-based decomposition is explored to remove noise as well as to reduce the file size of data for long-term monitoring.

Experimental validation of numerical study on thermoelectric-based heating in an integrated centrifugal microfluidic platform for polymerase chain reaction amplification.

A comprehensive study involving numerical analysis and experimental validation of temperature transients within a microchamber was performed for thermocycling operation in an integrated centrifugal microfluidic platform for polymerase chain reaction (PCR) amplification. Controlled heating and cooling of biological samples are essential processes in many sample preparation and detection steps for micro-total analysis systems. Specifically, the PCR process relies on highly controllable and uniform heating of nucleic acid samples for successful and efficient amplification. In these miniaturized systems, the heating process is often performed more rapidly, making the temperature control more difficult, and adding complexity to the integrated hardware system. To gain further insight into the complex temperature profiles within the PCR microchamber, numerical simulations using computational fluid dynamics and computational heat transfer were performed. The designed integrated centrifugal microfluidics platform utilizes thermoelectrics for ice-valving and thermocycling for PCR amplification. Embedded micro-thermocouples were used to record the static and dynamic thermal responses in the experiments. The data collected was subsequently used for computational validation of the numerical predictions for the system response during thermocycling, and these simulations were found to be in agreement with the experimental data to within ∼97%. When thermal contact resistance values were incorporated in the simulations, the numerical predictions were found to be in agreement with the experimental data to within ∼99.9%. This in-depth numerical modeling and experimental validation of a complex single-sided heating platform provide insights into hardware and system design for multi-layered polymer microfluidic systems. In addition, the biological capability along with the practical feasibility of the integrated system is demonstrated by successfully performing PCR amplification of a Group B Streptococcus gene.