Three-Dimensional Bioprinting of Strontium-Modified Controlled Assembly of Collagen Polylactic Acid Composite Scaffold for Bone Repair.

In recent years, the incidence of bone defects has been increasing year by year. Bone transplantation has become the most needed surgery after a blood transfusion and shows a rising trend. Three-dimensional-printed implants can be arbitrarily shaped according to the defects of tissues and organs to achieve perfect morphological repair, opening a new way for non-traumatic repair and functional reconstruction. In this paper, strontium-doped mineralized collagen was first prepared by an in vitro biomimetic mineralization method and then polylactic acid was homogeneously blended with the mineralized collagen to produce a comprehensive bone repair scaffold by a gas extrusion 3D printing method. Characterization through scanning electron microscopy, X-ray diffraction, and mechanical testing revealed that the strontium-functionalized composite scaffold exhibits an inorganic composition and nanostructure akin to those of human bone tissue. The scaffold possesses uniformly distributed and interconnected pores, with a compressive strength reaching 21.04 MPa. The strontium doping in the mineralized collagen improved the biocompatibility of the scaffold and inhibited the differentiation of osteoclasts to promote bone regeneration. This innovative composite scaffold holds significant promise in the field of bone tissue engineering, providing a forward-thinking solution for prospective bone injury repair.

Luminous Self-Assembled Fibers of Azopyridines and Quantum Dots Enabled by Synergy of Halogen Bond and Alkyl Chain Interactions.

Herein, a simple approach for the fabrication of luminous self-assembled fibers based on halogen-bonded azopyridine complexes and oleic acid-modified quantum dots (QDs) is reported. The QDs uniformly align on the edge of the self-assembled fibers through the formation of van der Waals force between the alkyl chain of oleic acid on the QD surface and the alkyl chain of the halogen-bonded complexes, 15Br or 15I. Furthermore, the intermolecular interaction mechanism was elucidated by using Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, and density functional theory (DFT) calculations. This approach results in retention of the fluorescence properties of the QDs in the fibers. In addition, the bromine-bonded fibers can be assembled into tailored directional fibers upon evaporation of the solvent (tetrahydrofuran) when using capillaries via the capillary force. Interestingly, the mesogenic properties of the halogen-bonded complexes are preserved in the easily prepared halogen-bonded fluorescent fibers; this provides new insight into the design of functional self-assembly materials.

In-Situ Oxidative Polymerization of Pyrrole Composited with Cellulose Nanocrystal by Reactive Ink-Jet Printing on Fiber Substrates.

A simple and novel method for the deposition of polypyrrole (PPy) and cellulose nanocrystal (CNC) composites on different fiber substrates by reactive ink-jet printing was proposed. PPy/CNCs composites were successfully prepared, and the surface resistance of conductive layer deposited on different fiber substrates is the least when the monomer concentration is 0.6 M. PPy/CNCs were deposited on polyethylene terephthalate (PET) to form a conductive layer by adding polyvinyl alcohol (PVA), and the optimum sintering temperature is 100 °C (monomer/PVA ratio 4.0, conductivity 0.769 S cm-1). The PPy/CNCs conductive layer deposited on the paper has the lowest surface resistance and the best adhesion, and the surface resistance of PPy/CNCs conductive layer decreases first and then increases with the increase of sulfonate concentration. Moreover, the volume of anion in sulfonate will affect the arrangement and aggregation of PPy molecular chain in composite materials. Appropriate sulfonate doping can improve the conductivity and stability of conductive paper, and the maximum conductivity is 0.813 S cm-1. Three devices based on PPy/CNCs conductive paper were proposed and fabricated. Therefore, this ink-jet printing provides a new method for the preparation of conductive materials, sensors, energy storage and electromagnetic shielding, etc.

LBL assembly of Ag@Ti3C2TXand chitosan on PLLA substrate to enhance antibacterial and biocompatibility.

Poly L-lactic acid (PLLA) is a non-toxic, biocompatible degradable polymer material with excellent mechanical properties after moulding. However, it faces challenges in the use of biomedical materials because of its intolerance to bacteria. Here, we use an easy-to-operate method to prepare a composite multilayer membrane: PLLA membrane was used as substrates to assemble positively charged chitosan and negatively charged Ag@MXene on the surface using the layer-by-layer (LBL) method. The assembly process was detected by fluorescein isothiocyanate-labelled chitosan and the thickness of the coating multilayer was also detected as 210.0 ± 12.1 nm for P-M membrane and 460.5 ± 26.5 nm for P-Ag@M membrane. The surface self-assembled multilayers exhibited 91.27% and 96.11% growth inhibition ratio againstEscherichia coliandStaphylococcus aureusstrains under 808 nm near-infrared laser radiation with a synergistic photothermal antibacterial effect. Furthermore, best biocompatibility of P-M and P-Ag@M membranes compare to PLLA membrane motivated us to further explore its application in biomedical materials.

3D bioprinting of an electroactive and self-healing polysaccharide hydrogels.

Polysaccharide hydrogels including alginate, agarose, hyaluronic acid, and chitosan have been widely used as scaffolds in 3D bio-printing field. Konjac glucomannan (KGM) exhibits excellent properties of water solubility, biocompatibility, and biodegradability. Herein composite hydrogels were prepared via Schiff-base reaction between the aldehyde group of oxidized konjac glucomannan (OKGM) and the amino group of branched polyethyleneimine (PEI). The OKGM/PEI composite hydrogel displayed self-healing ability and pH sensitivity and showed shear thinning capability, which is suitable for 3D bio-printing technology. Furthermore, the OKGM/PEI electroactive composite hydrogel was obtained by adding carbon nanotubes (CNTs). Then the rheological behavior and morphology of OKGM/PEI electroactive hydrogels were thoroughly characterized. The conductivities of OKGM/PEI electroactive composite hydrogels increased with increasing the content of CNTs. The rheological behavior and 3D bio-printability of OKGM/PEI electroactive hydrogels were also tested. It was found that CNTs can also improve the bio-printability of OKGM/PEI electroactive hydrogels. Thus, the OKGM/PEI electroactive hydrogels could be employed as scaffolds for muscle and cardiac nerve tissue regeneration.

Preparation recombination human-like collagen/fibroin scaffold and promoting the cell compatibility with osteoblasts.

On this basis, a novel recombinant human-like collagen (RHLC)/silk fibroin scaffold material with high porosity and controllable aperture was prepared. The compatibility of osteoblasts (OB) with the blends was tested in vitro. The morphology, adhesion and growth of scaffold cells were observed by scanning electron microscope and laser confocal microscope. Extensive measurements, including 3-[4, 5-dimethylthiazole-2-acyl]-2, 5-diphenyl tetrabrominate assays, intracellular total protein content, and alkaline phosphatase activity assays were performed after 7 days of culture. Survival and protein content increased in RHLC/fibroin stents. LSCM and SEM results confirmed that the cells grew better in the mixed scaffolds than in the pure silk scaffolds, and showed that the cells were easy to adhere and diffuse in the RHLC/silk scaffolds. RHLC/silk fibroin scaffolds are promising biomaterials for bone tissue engineering.

Development of Rapid Curing SiO2 Aerogel Composite-Based Quasi-Solid-State Dye-Sensitized Solar Cells through Screen-Printing Technology.

Grätzel's dye-sensitized solar cells (DSSCs) can readily convert sunlight into electricity, attracting considerable attention of global scientists. The fabrication efficiency of DSSCs was greatly limited by the slow fabrication (∼3.5-24 h) of quasi-solid (QS) electrolytes to date. In this study, novel composites of SiO2 aerogel with graphene (GR), multi-walled carbon nanotubes, or polyaniline were proposed in the fabrication of QS-state electrolytes. The morphology of these composites was characterized. The gels with SiO2 aerogels as QS electrolytes of DSSCs can be rapidly cured in ∼3 s. Using the screen-printing technology, these QS electrolytes can be readily utilized to construct the QS-DSSC to provide high efficiency and great stability. The photovoltaic parameters and interfacial charge-transfer resistances of the QS-DSSC incorporated with our synthetic composites were investigated in detail. Specifically, the SiO2 aerogel composed of GR (SiO2@GR) as a gel can greatly improve the performance of QS-DSSCs up to 8.25%. It is likely that these SiO2 aerogel composite electrolytes could provide a rapid curing process in the preparation of QS-state DSSCs, which might be useful to promote the development of DSSCs for future industrialization.

Trends and sex disparities in school bullying victimization among U.S. youth, 2011-2019.

BACKGROUND: The prevalence of being bullied traditionally among U.S. high school students is expected to reduce to 17.9%, according to Healthy People 2020 Initiatives. We examined trends in traditional victimization and cybervictimization with the latest large-scale time-series data in the United States. METHODS: We analyzed the data from the 2011-2019 national Youth Risk Behavior Survey (YRBS) to access the trends in traditional victimization and cybervictimization among U.S. high school students. We identified the temporal trends using multivariate logistic regression analyses, accounting for survey design features of YRBS. Participants included 72,605 high school students. RESULTS: The overall prevalence of victimization was 19.74% for traditional bullying and 15.38% for cyberbullying, suggesting that cyberbullying is not a low frequent phenomenon. The prevalence of victimization ranged from 20.19 to 19.04% for traditional victimization and 16.23 to 14.77% for cybervictimization, and the declined trends for the two kinds of bullying victimization were both statistically non-significant. The degree of overlap between the two kinds of bullying victimization was about 60%. Besides, female students reported more traditional victimization and cybervictimization than male peers within each survey cycle. CONCLUSIONS: No declined trends in traditional victimization and cybervictimization were observed during 2011-2019. Female students are more likely to experience school bullying. To achieve the Healthy People 2020 goal on bullying, more work is needed to explore the underlying reasons behind these unchanging trends.

Printable CsPbBr3 perovskite quantum dot ink for coffee ring-free fluorescent microarrays using inkjet printing.

Printable perovskite quantum dot (QD) ink is very important for achieving high quality coffee ring-free fluorescent microarrays for different kinds of emerging perovskite optoelectronic applications using inkjet printing. In this work, we prepared a printable CsPbBr3 perovskite QD ink by mixing high-boiling point dodecane with low-boiling point toluene as a solvent. The evaporation rate, viscosity and surface tension of the ink were carefully optimized by tuning the volume ratio of these two solvents for forming appropriate Marangoni flow, so as to balance the capillary flow and eliminate the coffee ring effect further. Successfully, CsPbBr3 perovskite microarrays with uniform surface, low roughness and no coffee rings were achieved by inkjet printing the optimized perovskite QD ink on a PVK (poly-(9-vinylcarbazole)) layer. Furthermore, we patterned the CsPbBr3 perovskite QD ink, and the printed patterns were only visible under ultraviolet (UV) light, which can be applied in invisible anti-counterfeiting labels and encryption in the future.

Organic-inorganic hybrid liquid crystals of azopyridine-enabled halogen-bonding towards sensing in aquatic environment.

In this study, organic-inorganic hybrid mesogens of silver nanoparticles (Ag NPs) and azopyridines (AzoPys) enabled by halogen bonding were prepared. Triple functions of the degree of orientation change, metal-enhanced fluorescence, and surface-enhanced Raman scattering were observed in Ag⋯Br-Br⋯AzoPy nanoparticles (12Br-Ag), which were induced by the in situ synthesis of Ag NPs in AzoPy. The bromine molecules were then linked by halogen bonding and electrostatic interaction resulting in the smectic A phase of 12Br-Ag. To demonstrate the potential of Br-Br⋯AzoPy (12Br) as a practical sensor, we used the 12Br compound to detect silver in an aqueous condition, and significant signals of the halogen-bonded complex-silver system were observed in the X-ray diffraction pattern and Raman spectra. Herein, we provide a novel perspective and design principle for the practical applications of organic-inorganic hybrid liquid crystals in environmental monitoring.

High-Throughput Identification and Screening of Single Microbial Cells by Nanobowl Array.

High-throughput screening and fast identification of single bacterial cells are crucial for clinical diagnosis, bioengineering, and fermentation engineering. Although single-cell technologies have been developed extensively in recent years, the single-cell technologies for bacteria still need further exploration. In this study, we demonstrate an identification and screening technology for single bacterial cells based on a large-scale nanobowl array, which is well-ordered and size-adjustable for use with different kinds of bacteria. When the culture medium with monodispersed bacteria was placed on the nanobowl array, it successfully enabled loading of single bacterium into a single nanobowl. Because of the limitative size and depth of the nanobowls, mixture of different bacteria species could be screened according to their sizes. In addition, with the help of a low electrical current, the bacteria can be further screened according to their intrinsic surface charges. If combined with micromanipulation technology, high-throughput single bacterial selection can be achieved in future.

Surface-Coated Thermally Expandable Microspheres with a Composite of Polydisperse Graphene Oxide Sheets.

Surface-modified thermally expandable microcapsules (TEMs) hold potential for applications in various fields. In this work, we discussed the possible surface coating mechanism and reported the properties of TEMs coated with polyaniline (PANI) and polydisperse graphene oxide sheets (ionic liquid-graphene oxide hybrid nanomaterial (ILs-GO)). The surface coating of PANI/ ILs-GO increased the corresponding particle size and its distribution range. The morphologies analyzed by scanning electron microscopy indicated that no interfacial gap was observed between the microspheres ink and substrate layer during the substrate application. The thermal properties were determined by thermogravimetric and differential thermal analyses. The addition of ILs-GO to the polyaniline coating significantly improved the thermal expansion and thermal conductivity of the microcapsules. The evaporation of hexane present in the core of TEMs was not prevented by the coating of PANI/ ILs-GO. The printing application of TEMs showed excellent adaptability to various flexible substrates with great 3D appearance. By incorporating a flame retardant agent into TEMs coated by PANI/ILs-GO, finally, these TEMs also demonstrated a great flame retardant ability. We expect that these TEM-coated PANI/ ILs-GO are likely to have the potential to improve the functional properties for various applications.

Printed and Flexible Capacitive Pressure Sensor with Carbon Nanotubes based Composite Dielectric Layer.

Flexible pressure sensors have attracted tremendous attention from researchers for their widely applications in tactile artificial intelligence, electric skin, disease diagnosis, and healthcare monitoring. Obtaining flexible pressure sensors with high sensitivity in a low cost and convenient way remains a huge challenge. In this paper, the composite dielectric layer based on the mixture of carbon nanotubes (CNTs) with different aspect ratios and polydimethylsiloxane (PDMS) was employed in flexible capacitive pressure sensor to increase its sensitivity. In addition, the screen printing instead of traditional etching based methods was used to prepare the electrodes array of the sensor. The results showed that the aspect ratio and weight fraction of the CNTs play an important role in improving the sensitivity of the printed capacitive pressure sensor. The prepared capacitive sensor with the CNTs/PDMS composite dielectric layer demonstrated a maximum sensitivity of 2.9 kPa-1 in the pressure range of 0-450 Pa, by using the CNTs with an aspect ratio of 1250-3750 and the weight fraction of 3.75%. The mechanism study revealed that the increase of the sensitivity of the pressure sensor should be attributed to the relative permittivity increase of the composite dielectric layer under pressure. Meanwhile, the printed 3 × 3 and 10 × 10 sensor arrays showed excellent spatial resolution and uniformity when they were applied to measure the pressure distribution. For further applications, the flexible pressure sensor was integrated on an adhesive bandage to detect the finger bending, as well as used to create Morse code by knocking the sensor to change their capacitance curves. The printed and flexible pressure sensor in this study might be a good candidate for the development of tactile artificial intelligence, intelligent medical diagnosis systems and wearable electronics.

A Review: Preparation, Performance, and Applications of Silicon Oxynitride Film.

Silicon oxynitride (SiNxOy) is a highly promising functional material for its luminescence performance and tunable refractive index, which has wide applications in optical devices, non-volatile memory, barrier layer, and scratch-resistant coatings. This review presents recent developments, and discusses the preparation methods, performance, and applications of SiNxOy film. In particular, the preparation of SiNxOy film by chemical vapor deposition, physical vapor deposition, and oxynitridation is elaborated in details.

Nano-Silver Ink of High Conductivity and Low Sintering Temperature for Paper Electronics.

Highly conductive ink with low sintering temperature is important for printed electronics on paper substrate. Silver nanoparticles (Ag NPs) of different average radii ranging from 48 to 176 nm were synthesized by adjusting the Ag+ concentration in the reaction process. The electric resistivity of the Ag NP-based ink film in relation to Ag NP size, sintering temperature, amount of PVP capping agent on Ag NP surface, and morphology evolution of the film during heating process was investigated. It was found that the resistivity of the films reduced very rapidly with increasing particle size due above all to reduced amount of protective agent capping on the Ag NPs. A semi-empirical relationship between the resistivity and the particle size was proposed. With the help of this mathematical expression, one gains both systematic and detailed insight to the resistivity evaluation with regard to the Ag particle size. The optimal electric resistivity of 4.6 µΩ cm was achieved at 140 °C for 10 min which was very close to the resistivity value of bulk Ag (1.58 µΩ cm). Mechanical flexibility of the printed electronics with the Ag NP-based ink on paper substrates was investigated. The prints on the art coated paper exhibited better flexibility compared to that on the photopaper. This might be attributed to the surface coating composition, surface morphology of the paper, and their corresponding ink absorption property.

Synthesis and Applications of Silver Nanowires for Transparent Conductive Films.

Flexible transparent conductive electrodes (TCEs) are widely applied in flexible electronic devices. Among these electrodes, silver (Ag) nanowires (NWs) have gained considerable interests due to their excellent electrical and optical performances. Ag NWs with a one-dimensional nanostructure have unique characteristics from those of bulk Ag. In past 10 years, researchers have proposed various synthesis methods of Ag NWs, such as ultraviolet irradiation, template method, polyol method, etc. These methods are discussed and summarized in this review, and we conclude that the advantages of the polyol method are the most obvious. This review also provides a more comprehensive description of the polyol method for the synthesis of Ag NWs, and the synthetic factors including AgNO3 concentration, addition of other metal salts and polyvinyl pyrrolidone are thoroughly elaborated. Furthermore, several problems in the fabrication of Ag NWs-based TCEs and related devices are reviewed. The prospects for applications of Ag NWs-based TCE in solar cells, electroluminescence, electrochromic devices, flexible energy storage equipment, thin-film heaters and stretchable devices are discussed and summarized in detail.

Silver Nanoparticles Based Ink with Moderate Sintering in Flexible and Printed Electronics.

Printed electronics on flexible substrates has attracted tremendous research interest research thanks its low cost, large area production capability and environmentally friendly advantages. Optimal characteristics of silver nanoparticles (Ag NPs) based inks are crucial for ink rheology, printing, post-print treatment, and performance of the printed electronics devices. In this review, the methods and mechanisms for obtaining Ag NPs based inks that are highly conductive under moderate sintering conditions are summarized. These characteristics are particularly important when printed on temperature sensitive substrates that cannot withstand sintering of high temperature. Strategies to tailor the protective agents capping on the surface of Ag NPs, in order to optimize the sizes and shapes of Ag NPs as well as to modify the substrate surface, are presented. Different (emerging) sintering technologies are also discussed, including photonic sintering, electrical sintering, plasma sintering, microwave sintering, etc. Finally, applications of the Ag NPs based ink in transparent conductive film (TCF), thin film transistor (TFT), biosensor, radio frequency identification (RFID) antenna, stretchable electronics and their perspectives on flexible and printed electronics are presented.

Recent Developments for Flexible Pressure Sensors: A Review.

Flexible pressure sensors are attracting great interest from researchers and are widely applied in various new electronic equipment because of their distinct characteristics with high flexibility, high sensitivity, and light weight; examples include electronic skin (E-skin) and wearable flexible sensing devices. This review summarizes the research progress of flexible pressure sensors, including three kinds of transduction mechanisms and their respective research developments, and applications in the fields of E-skin and wearable devices. Furthermore, the challenges and development trends of E-skin and wearable flexible sensors are also briefly discussed. Challenges of developing high extensibility, high sensitivity, and flexible multi-function equipment still exist at present. Exploring new sensing mechanisms, seeking new functional materials, and developing novel integration technology of flexible devices will be the key directions in the sensors field in future.

Azopyridine-Containing Three-arm Star Compounds with Aggregation-induced Fluorescence.

Three-arm star azopyridinium salts self-organize into various morphologies in water/organic mixed solvents. Interesting AIE and self-assembling features are observed due to the strong interaction of the azopyridinium moieties with the highly polar H2 O molecules causing the salts to aggregate, which restricts the molecular motion and induces the fluorescence.

Branched CdO/ZnO Core/Shell Heterogeneous Structure and Its Enhanced Photoelectrocatalytic Performance.

Branched nanostructures of semiconductors based on one-dimensional heterostructures have many promising applications in optoelectronics, supercapacitors, photocatalysts, etc. Here, we report a novel branched core/shell CdO/ZnO hetero-nanostructure that resembles a Crimson bottlebrush (Callistemon Citrinus) but with intriguing hexagonal symmetry. The nanomaterials were fabricated via an improved one-step chemical vapor deposition method and consist of a CdO wire as the core and ZnO as the shell. With cadmium acting as a catalyst, ZnO nanowires grow as perpendicular branches from the CdO/ZnO one-dimensional core/shell structure. The nanostructures were characterized with X-ray diffraction scanning and transmission electron microscopy. A homogeneous epitaxial growth mechanism has been postulated for the formation of the nanostructure. The materials show a broad and strong absorption ranging from visible to ultraviolet and a better photoelectrocatalytic properties in comparison to pure ZnO or CdO. Our synthetic strategy may open up a new way for controlled preparation of one-dimensional nanomaterials with core/shell heterostructure, which could find potential applications in solar cells and opto-electrochemical water-splitting devices.