Optimization of CoFe2O4 nanoparticles and graphite fillers to endow thermoplastic polyurethane nanocomposites with superior electromagnetic interference shielding performance.

The rapid growth, integration, and miniaturization of electronics have raised significant concerns about how to handle issues with electromagnetic interference (EMI), which has increased demand for the creation of EMI shielding materials. In order to effectively shield against electromagnetic interference (EMI), this study developed a variety of thermoplastic polyurethane (TPU)-based nanocomposites in conjunction with CoFe2O4 nanoparticles and graphite. The filler percentage and nanocomposite thickness were tuned and optimized. The designed GF15-TPU nanocomposite, which has a 5 mm thickness, 15 weight percent cobalt ferrite nanoparticles, and 35 weight percent graphite, showed the highest total EMI shielding effectiveness value of 41.5 dB in the 8.2-12.4 GHz frequency range, or 99.993% shielding efficiency, out of all the prepared polymer nanocomposites. According to experimental findings, the nanocomposite's dipole polarization, interfacial polarization, conduction loss, eddy current loss, natural resonance, exchange resonance, multiple scattering, and high attenuation significantly contribute to improving its electromagnetic interference shielding properties. The created TPU-based nanocomposites containing graphite and CoFe2O4 nanoparticles have the potential to be used in communication systems, defense, spacecraft, and aircraft as EMI shielding materials.

Design and Fabrication of Electrospun PLA-Based Silica-Modified Composite Nanofibers with Antibacterial Properties for Perspective Wound Treatment.

The aim of this study was to develop a novel amikacin (AMI) delivery system with prolonged release based on composite electrospun nanofibers of PLA supplemented with AMI-loaded Si nanoparticles of different morphology. The resultant materials were characterized in terms of their physical properties (scanning electron microscopy, Brunauer-Emmett-Teller analysis, thermogravimetric analysis, water contact angle). High-Performance Liquid Chromatography was used to determine the AMI content in the liquid fractions obtained from the release study. The results show that nanofibers of fumed silica exhibited an aggregated, highly porous structure, whereas nanofibers of mesoporous silica had a spherical morphology. Both silica nanoparticles had a significant effect on the hydrophilic properties of PLA nanofiber surfaces. The liquid fractions were investigated to gauge the encapsulation efficiency (EE) and loading efficiency (LE) of AMI, demonstrating 66% EE and 52% LE for nanofibers of fumed silica compared to nanofibers of mesoporous silica nanoparticles (52% EE and 12.7% LE). The antibacterial activity of the AMI-loaded nanofibers was determined by the Kirby-Bauer Method. These results demonstrated that the PLA-based silica nanofibers effectively enhanced the antibacterial properties against the Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae.

Controlled Drug Delivery Device for Cornea Treatment and Novel Method for Its Testing.

A new solution for local anesthetic and antibiotic delivery after eye surgery is presented. A contact lens-shaped collagen drug carrier was created and loaded by Levofloxacin and Tetracaine with a riboflavin crosslinked surface layer, thus impeding diffusion. The crosslinking was confirmed by Raman spectroscopy, whereas the drug release was investigated using UV-Vis spectrometry. Due to the surface barrier, the drug gradually releases into the corneal tissue. To test the function of the carrier, a 3D printed device and a new test method for a controlled drug release, which mimics the geometry and physiological lacrimation rate of the human eye, were developed. The experimental setup with simple geometry revealed that the prepared drug delivery device can provide the prolonged release profile of the pseudo-first-order for up to 72 h. The efficiency of the drug delivery was further demonstrated using a dead porcine cornea as a drug recipient, without the need to use live animals for testing. Our drug delivery system significantly surpasses the efficiency of antibiotic and anesthetic eyedrops that would have to be applied approximately 30 times per hour to achieve the same dose as that delivered continuously by our device.

Stable Magnetorheological Fluids Containing Bidisperse Fillers with Compact/Mesoporous Silica Coatings.

A drawback of magnetorheological fluids is low kinetic stability, which severely limits their practical utilization. This paper describes the suppression of sedimentation through a combination of bidispersal and coating techniques. A magnetic, sub-micro additive was fabricated and sequentially coated with organosilanes. The first layer was represented by compact silica, while the outer layer consisted of mesoporous silica, obtained with the oil-water biphase stratification method. The success of the modification technique was evidenced with transmission electron microscopy, scanning electron microscopy/energy-dispersive X-ray spectroscopy and Fourier-transform infrared spectroscopy. The coating exceptionally increased the specific surface area, from 47 m2/g (neat particles) up to 312 m2/g, which when combined with lower density, resulted in remarkable improvement in the sedimentation profile. At this expense, the compact/mesoporous silica slightly diminished the magnetization of the particles, while the magnetorheological performance remained at an acceptable level, as evaluated with a modified version of the Cross model. Sedimentation curves were, for the first time in magnetorheology, modelled via a novel five-parameter equation (S-model) that showed a robust fitting capability. The sub-micro additive prevented the primary carbonyl iron particles from aggregation, which was projected into the improved sedimentation behavior (up to a six-fold reduction in the sedimentation rate). Detailed focus was also given to analyze the implications of the sub-micro additives and their surface texture on the overall behavior of the bidisperse magnetorheological fluids.

Unravelling the highly efficient synthesis of individual carbon nanodots from casein micelles and the origin of their competitive constant-blue-red wavelength shift luminescence mechanism for versatile applications.

Synthesis of casein-derived carbon nanodots (CND) using a microwave-assisted approach, giving a high product yield (25%), is reported. Casein was used as a sustainable carbon source, and polyvinylpyrrolidone was used as a stabilizer for the nanodots. The size of the prepared amorphous CND corresponds to individual casein coils, which were only partially carbonized. They were obtained due to the disintegration of casein micelles and submicelles within the microwave-assisted solvothermal process. The resulting nanodots had bright photoluminescence, and their electronic structure and optical properties were investigated. A novel competitive model of their luminescence mechanism was introduced to explain a phenomenon beyond the standard models. The synthesized carbon nanodots were used as luminescent ink for anticounterfeit applications. A polymer matrix nanocomposite was prepared by dispersing the nanodots in a flexible and robust poly(styrene-ethylene-butylene-styrene) tri-block copolymer (SEBS) using the solution cast method. For the first time, the effect of CND on the luminescence and mechanical properties of the SEBS/CND self-supporting films was studied. The film was also studied as a phosphor for light-emitting diodes, with a unique experimental setup to avoid self-absorption, which results in low efficiency and eliminates the excess UV transmitted. Because of their high luminescence, photostability, and mechanical properties, these CND could be used as luminescent labels in the packaging and optoelectronics industries.

Inkjet Printability Assessment of Weakly Viscoelastic Fluid: A Semidilute Polyvinylpyrrolidone Solution Ink Case Study.

Here, we present an integrated approach to the weakly viscoelastic fluid printability assessment by using global dimensionless criteria (DC). The problem was studied on a model semidiluted polyvinylpyrrolidone water-based ink. For the study purpose, the ink composition was kept as simple as possible. First, the solution density, viscosity, and surface tension were determined. Obtained data were used for testing limitations of DC printability diagrams already available for Newtonian fluids. A replotted version of the original Kim and Baek's map was developed emphasizing the importance of surface tension in the drop formation process. Another set of DC (e.g., Ec and De) was also used for a real evaluation of the viscoelasticity effect on both jetting conditions and drop formation. The polymer relaxation time as a crucial parameter for viscoelasticity was shown to be calculated using the Kuhn segment length rather than from Zimm and Rouse theories for diluted polymer systems. Then, a two-dimensional diagram using four DC (Oh and De with Ec and El as parameters) is proposed based on the famous McKinley's work. The diagram describes the interplay of possible forces responsible for filament thinning and breakup processes. Obtained results were supported by further experiments involving drop ejection and formation, determination of critical polymer concentration, and others. The proposed diagram promises a useful initial step in further investigations of viscoelasticity of polymer compounds by inkjet printing.

Controlled release of enrofloxacin by vanillin-crosslinked chitosan-polyvinyl alcohol blends.

In transdermal drug delivery applications uniform drug distribution and sustained release are of great importance to decrease the side effects. In this direction in the present research, vanillin crosslinked chitosan (CS) and polyvinyl alcohol (PVA) blend based matrix-type transdermal system was prepared by casting and drying of aqueous solutions for local delivery of enrofloxacin (ENR) drug. Subsequently, the properties including the morphology, chemical structure, thermal behavior, tensile strength, crosslinking degree, weight uniformity, thickness, swelling and drug release of the CS-PVA blend films before and after crosslinking were characterized. In vitro drug release profiles showed the sustained release of ENR by the incorporation of vanillin as a crosslinker into the CS-PVA polymer matrix. Furthermore, the release kinetic profiles revealed that the followed mechanism for all samples was Higuchi and the increase of vanillin concentration in the blend films resulted in the change of diffusion mechanism from anomalous transport to Fickian diffusion. Overall, the obtained results suggest that the investigated vanillin crosslinked CS-PVA matrix-type films are potential candidates for transdermal drug delivery system.

Fully Inkjet-Printed CuO Sensor on Flexible Polymer Substrate for Alcohol Vapours and Humidity Sensing at Room Temperature.

This work focuses on an inkjet-fabricated sensor based on copper oxide nanostructured particles on polymer flexible substrate for the sensing of alcohol vapours and humidity at room temperature. Nanoparticles were prepared by a microwave-assisted solvothermal sealed vessel synthesis method. The ink composition was developed on the basis of viscosity and surface tension optimization by the addition of polymeric steric surfactant and dispersant. The printing process was optimized with the help of non-dimensional criteria. Silver nanoink was used for the printing of an interdigitated pattern on a PET substrate which was overprinted by the copper oxide ink, thus obtaining a flexible flat sensor. Material design and all fabrication steps of the sensor respected the temperature limitation given by the thermal stability of the polymer substrate. Printed layers and motifs were characterized microscopically and by resistance measurement. The effectiveness of the prepared sensor was demonstrated and studied by measuring the response to saturated vapours at room temperature. The sensing layer showed the opposite resistance response to stimuli than expected for the well-known p-type sensing mechanism of CuO sensors operated at high temperatures. In addition to vapour sorption, condensation and desorption influencing electron, proton and ionic conductivity, manifestation of another mechanism was observed and an explanation suggested in terms of the electrochemical mechanism.

Water-Based Indium Tin Oxide Nanoparticle Ink for Printed Toluene Vapours Sensor Operating at Room Temperature.

This study is focused on the development of water-based ITO nanoparticle dispersions and ink-jet fabrication methodology of an indium tin oxide (ITO) sensor for room temperature operations. Dimensionless correlations of material-tool-process variables were used to map the printing process and several interpretational frameworks were re-examined. A reduction of the problem to the Newtonian fluid approach was applied for the sake of simplicity. The ink properties as well as the properties of the deposited layers were tested for various nanoparticles loading. High-quality films were prepared and annealed at different temperatures. The best performing material composition, process parameters and post-print treatment conditions were used for preparing the testing sensor devices. Printed specimens were exposed to toluene vapours at room temperature. Good sensitivity, fast responses and recoveries were observed in ambient air although the n-type response mechanism to toluene is influenced by moisture in air and baseline drift was observed. Sensing response inversion was observed in an oxygen and moisture-free N2 atmosphere which is explained by the charge-transfer mechanism between the adsorbent and adsorbate molecules. The sensitivity of the device was slightly better and the response was stable showing no drifts in the protective atmosphere.