Ultrastrong, smooth, and shiny graphene paper with a layered structure (see figure) is prepared by vacuum filtration of a well‐dispersed graphene dispersion. Moderate thermal annealing further ...enhances its mechanical properties and electrical conductivity. A combination of exceptional mechanical strength, thermal stability, high electrical conductivity, and biocompability makes this unique material promising for many technological applications.
The use of software measures for project management and software process improvement has been encouraged for many years. However, the low level of acceptance and use of software measures in practice ...has been a constant concern. In this paper we propose and test a model which explains and predicts the use of software measures. The model is based on the technology acceptance model (TAM) and operationalizes the perceived usefulness construct according to the “desirable properties of software measures.” Our research provides guidance for software engineers in selecting among different software measures and for software metrics coordinators who are planning measurement programs.
Abstract The brain is an enormously complex organ structured into various regions of layered tissue. Researchers have attempted to study the brain by modeling the architecture using two dimensional ...(2D) in vitro cell culturing methods. While those platforms attempt to mimic the in vivo environment, they do not truly resemble the three dimensional (3D) microstructure of neuronal tissues. Development of an accurate in vitro model of the brain remains a significant obstacle to our understanding of the functioning of the brain at the tissue or organ level. To address these obstacles, we demonstrate a new method to bioprint 3D brain-like structures consisting of discrete layers of primary neural cells encapsulated in hydrogels. Brain-like structures were constructed using a bio-ink consisting of a novel peptide-modified biopolymer, gellan gum-RGD (RGD-GG), combined with primary cortical neurons. The ink was optimized for a modified reactive printing process and developed for use in traditional cell culturing facilities without the need for extensive bioprinting equipment. Furthermore the peptide modification of the gellan gum hydrogel was found to have a profound positive effect on primary cell proliferation and network formation. The neural cell viability combined with the support of neural network formation demonstrated the cell supportive nature of the matrix. The facile ability to form discrete cell-containing layers validates the application of this novel printing technique to form complex, layered and viable 3D cell structures. These brain-like structures offer the opportunity to reproduce more accurate 3D in vitro microstructures with applications ranging from cell behavior studies to improving our understanding of brain injuries and neurodegenerative diseases.
Biodegradable active implantable devices can be used to diagnose and/or treat disease and eventually disappear without surgical removal. If an “external” energy source is required for effective ...operation then a biocompatible and biodegradable battery would be ideal. In this study, a partially biodegradable Mg‐air bioelectric battery (biobattery) is demonstrated using a silk fibroin‐polypyrrole (SF‐PPy) film cathode coupled with bioresorbable Mg alloy anode in phosphate buffered saline (PBS) electrolyte. PPy is chemically coated onto one side of the silk substrate. SF‐PPy film shows a conductivity of ≈1.1 S cm−1 and a mild catalytic activity toward oxygen reduction. It degrades in a concentrated buffered protease XIV solution, with a weight loss of 82% after 15 d. The assembled Mg‐air biobattery exhibits a discharge capacity up to 3.79 mA h cm−2 at a current of 10 μA cm−2 at room temperature, offering a specific energy density of ≈4.70 mW h cm−2. This novel partially biodegradable battery provides another step along the route to biodegradable batteries.
A partially biodegradable bilayer‐structured film composed of silk fibroin and polypyrrole demonstrates an 82% mass loss after 15 d incubation in buffered protease XIV solution. It can offer an energy density of ≈4.70 mW h cm−2 when coupled with Mg alloy in phosphate buffered saline. This battery system may provide appropriate power for temporary implantable electronics coupled with the required degradation profile.
The development of cell printing is vital for establishing biofabrication approaches as clinically relevant tools. Achieving this requires bio-inks which must not only be easily printable, but also ...allow controllable and reproducible printing of cells. This review outlines the general principles and current progress and compares the advantages and challenges for the most widely used biofabrication techniques for printing cells: extrusion, laser, microvalve, inkjet and tissue fragment printing. It is expected that significant advances in cell printing will result from synergistic combinations of these techniques and lead to optimised resolution, throughput and the overall complexity of printed constructs.
Celotno besedilo
Dostopno za:
CEKLJ, DOBA, EMUNI, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK
Although electrochemical CO2 reduction is one of the most promising ways to convert atmospheric CO2 into value-added chemicals, there are still numerous limitations to overcome to achieve highly ...efficient CO2 conversion performance. Herein, we report for the first time the development and use of a three-dimensional iron porphyrin-based graphene hydrogel (FePGH) as an electrocatalyst for extremely efficient robust CO2 reduction to CO. Electrocatalytic CO2 conversion was performed in aqueous medium with FePGH, which has a highly porous and conductive 3D graphene structure, resulting in high catalytic activity for CO production with ∼96.2% faradaic efficiency at a very low overpotential of 280 mV. Furthermore, FePGH showed considerable catalytic durability maintaining a consistent CO yield (96.4% FE) over 20 h electrolysis at the same overpotential, corresponding to the highest cathodic energy efficiency yet observed of 79.7% compared to other state-of-the-art immobilised metal complex electrocatalysts. This approach to fabricating a 3D graphene-based hydrogel electrocatalyst should provide an exciting new avenue for the development of other kinds of molecular electrocatalysts.
Key points in the formation of liquid crystalline (LC) dispersions of graphene oxide (GO) and their processability via wet‐spinning to produce long lengths of micrometer‐dimensional fibers and yarns ...are addressed. Based on rheological and polarized optical microscopy investigations, a rational relation between GO sheet size and polydispersity, concentration, liquid crystallinity, and spinnability is proposed, leading to an understanding of lyotropic LC behavior and fiber spinnability. The knowledge gained from the straightforward formulation of LC GO “inks” in a range of processable concentrations enables the spinning of continuous conducting, strong, and robust fibers at concentrations as low as 0.075 wt%, eliminating the need for relatively concentrated spinning dope dispersions. The dilute LC GO dispersion is proven to be suitable for fiber spinning using a number of coagulation strategies, including non‐solvent precipitation, dispersion destabilization, ionic cross‐linking, and polyelectrolyte complexation. One‐step continuous spinning of graphene fibers and yarns is introduced for the first time by in situ spinning of LC GO in basic coagulation baths (i.e., NaOH or KOH), eliminating the need for post‐treatment processes. The thermal conductivity of these graphene fibers is found to be much higher than polycrystalline graphite and other types of 3D carbon based materials.
New insights are provided into the processing of liquid crystalline graphene oxide (GO) dispersion (containing large GO sheets) demonstrating a facile and scalable production of GO and reduced GO fibers and yarns with exciting properties such as high thermal conductivity. These results provide a universal platform for the development of solution‐based processing methods, properties, and applications of liquid crystalline GO‐based architectures.
Highly stretchable, actuatable, electrically conductive knitted textiles based on Spandex (SPX)/CNT (carbon nanotube) composite yarns were prepared by an integrated knitting procedure. SPX filaments ...were continuously wrapped with CNT aerogel sheets and supplied directly to an interlocking circular knitting machine to form three-dimensional electrically conductive and stretchable textiles. By adjusting the SPX/CNT feed ratio, the fabric electrical conductivities could be tailored in the range of 870 to 7092 S/m. The electrical conductivity depended on tensile strain, with a linear and largely hysteresis-free resistance change occurring on loading and unloading between 0% and 80% strain. Electrothermal heating of the stretched fabric caused large tensile contractions of up to 33% and generated a gravimetric mechanical work capacity during contraction of up to 0.64 kJ/kg and a maximum specific power output of 1.28 kW/kg, which far exceeds that of mammalian skeletal muscle. The knitted textile provides the combination of strain sensing and the ability to control dimensions required for smart clothing that simultaneously monitors the wearer’s movements and adjusts the garment fit or exerts forces or pressures on the wearer, according to needs. The developed processing method is scalable for the fabrication of industrial quantities of strain sensing and actuating smart textiles.
The cyber–physical nature of biotechnology raises unprecedented security concerns. Computers can be compromised by encoding malware in DNA sequences, and biological threats can be synthesized using ...publicly available data. Trust within the biotechnology community creates vulnerabilities at the interface between cyberspace and biology. Awareness is a prerequisite to managing these risks.
Wearable energy storage devices are of practical interest, but few have been commercially exploited. Production of electrodes with extended cycle life, as well as high energy and power densities, ...coupled with flexibility, remains a challenge. Herein, we have demonstrated the development of a high-performance hybrid carbon nanotube (CNT) fiber-based supercapacitor for the first time using conventional wet-spinning processes. Manganese dioxide (MnO
) nanoflakes were deposited onto the as-prepared CNT fibers by electrodeposition to form highly flexible nanocomposites fibers. As-prepared fibers were characterized by electron microscopy, electrical, mechanical, and electrochemical measurements. It was found that the specific capacitance was over 152 F g
(156 F cm
), which is about 500% higher than the multi-walled carbon nanotube/MnO
yarn-based supercapacitors. The measured energy density was 14.1 Wh kg
at a power density of 202 W kg
. These values are 232% and 32% higher than the energy density and power density of MWNT/MnO
yarn-based supercapacitor, respectively. It was found that the cyclic retention ability was more stable, revealing a 16% increase after 10 000 cycles. Such substantial enhancements of key properties of the hybrid material can be associated with the synergy of CNT and MnO
nanoparticles in the fiber structure. The use of wet-spun hybrid CNT for fiber-based supercapacitors has been demonstrated.
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