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In situ 3D printing is an emerging technique designed for patient-specific needs and performed directly in the patient’s tissues in the operating room. While this technology has progressed rapidly, several improvements are needed to push it forward for widespread utility, including ink formulations and optimization for in situ context. Silk fibroin inks emerge as a viable option due to the diverse range of formulations, aqueous processability, robust and tunable mechanical properties, and self-assembly via biophysical adsorption to avoid exogenous chemical or photochemical sensitizer additives, among other features. In this review, we focus on this new frontier of 3D in situ printing for tissue regeneration, where silk is proposed as candidate biomaterial ink due to the unique and useful properties of this protein polymer. In vitro 3D printing techniques have challenges that limit their clinical translation, including multistep processes, mismatches with patient-specific defects, risk of contamination, and postprocessing manipulation requirements.In situ 3D printing, the next frontier for 3D printing, aims to fabricate new tissues and organs in vivo, in the surgical setting, directly in the patient.Inks remain a challenge for this transition to in situ 3D printing, requiring fast gelation, high shape fidelity, minimal if any postprocessing, robust mechanical properties tunable to the target tissue, and biocompatibility.Versatile and appropriate inks, such as those developed from silk fibroin, offer a foundation for this translation, based on their unique amphiphilic structure, versatility in physical crosslinking, mechanical properties, biocompatibility, and tunable degradation.

Photodetectors based on transition metal dichalcogenides (TMDs) have been widely reported in the literature and molybdenum disulfide (MoS2) has been the most extensively explored for photodetection applications. The properties of MoS2, such as direct band gap transition in low dimensional structures, strong light–matter interaction and good carrier mobility, combined with the possibility of fabricating thin MoS2 films, have attracted interest for this material in the field of optoelectronics. In this work, MoS2-based photodetectors are reviewed in terms of their main performance metrics, namely responsivity, detectivity, response time and dark current. Although neat MoS2-based detectors already show remarkable characteristics in the visible spectral range, MoS2 can be advantageously coupled with other materials to further improve the detector performance Nanoparticles (NPs) and quantum dots (QDs) have been exploited in combination with MoS2 to boost the response of the devices in the near ultraviolet (NUV) and infrared (IR) spectral range. Moreover, heterostructures with different materials (e.g., other TMDs, Graphene) can speed up the response of the photodetectors through the creation of built-in electric fields and the faster transport of charge carriers. Finally, in order to enhance the stability of the devices, perovskites have been exploited both as passivation layers and as electron reservoirs.

The shortage of tissues and organs for transplantation is an urgent clinical concern. In situ 3D printing is an advanced 3D printing technique aimed at printing the new tissue or organ directly in the patient. The ink for this process is central to the outcomes, and must meet specific requirements such as rapid gelation, shape integrity, stability over time, and adhesion to surrounding healthy tissues. Among natural materials, silk fibroin exhibits fascinating properties that have made it widely studied in tissue engineering and regenerative medicine. However, further improvements in silk fibroin inks are needed to match the requirements for in situ 3D printing. In the present study, silk fibroin-based inks were developed for in situ applications by exploiting covalent crosslinking process consisting of a pre-photo-crosslinking prior to printing and in situ enzymatic crosslinking. Two different silk fibroin molecular weights were characterized and the synergistic effect of the covalent bonds with shear forces enhanced the shift in silk secondary structure toward β-sheets, thus, rapid stabilization. These hydrogels exhibited good mechanical properties, stability over time, and resistance to enzymatic degradation over 14 days, with no significant changes over time in their secondary structure and swelling behavior. Additionally, adhesion to tissues in vitro was demonstrated. [Display omitted] •With in situ 3D printing new tissues/organs are printed directly into the patient.•Silk fibroin-based inks were developed for in situ 3D printing applications.•Double crosslinking process was applied to avoid any post processing manipulation.•Synergistic effect of the crosslinking process with the shear rate in the nozzle: structure stability.•The resultant hydrogels exhibited resistance to degradation and good hBM-MSCs adhesion.

Barium titanate (BT) recently gained new interest in the preparation of dielectric and piezoelectric lead-free materials for applications in sensors, electronics, energy harvesting and storage fields. Barium titanate nanocomposites can achieve attractive performance, provided that the compatibility between ceramic particles and polymeric matrices is enhanced to the benefit of the physical properties of the final composite. Tuning the particle–matrix interface through particle functionalization represents a viable solution. In this work, surface functionalization of BT nanoparticles (NPs), obtained by hydrothermal synthesis, with 3-glycidyloxypropyltrimethoxysilane, 2-[(acetoxy(polyethyleneoxy)propyl]triethoxysilane and triethoxysilylpropoxy(polyethyleneoxy)dodecanoate, was performed after optimizing the hydroxylation process of the NPs to improve their surface reactivity and increase the yield of grafting. Solid-state nuclear magnetic resonance and thermogravimetric analysis were used to quantify the molecules grafted onto the ceramic nanoparticles. Both bare and functionalized particles were employed in the realization of epoxy- and polydimethylsiloxane (PDMS)-based nanocomposites. Functionalization was proven to be beneficial for particle dispersibility and effective for particle alignment in the PDMS matrix. Moreover, the dielectric constant measurements revealed the potential of PDMS-based nanocomposites for applications in the field of dielectric elastomers.

Silk sericin (SS) is a natural polymer widely studied in the design of biodegradable materials for cosmetic, biomedical, food, and chemical applications. This work was designed to explore the molecular and structural characteristics of SS extracted from different silk sources with different processing degrees: high-quality cocoons (NCs), defective cocoons (DCs), and raw silk yarn (Y). The last two sources have been less studied. SS solutions were obtained from each source using the high-temperature and high-pressure degumming method (HTHP). The molecular weight distribution and amino acid composition of SS extracts were determined using gel permeation chromatography (GPC) and reversed-phase chromatography (RP HPLC), respectively. SS films were formed from each solution and then characterized by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), nuclear magnetic resonance spectroscopy (NMR), and differential scanning calorimetry (DSC). Water uptake and degradation of SS films were also evaluated. The molecular characteristics of SS extracts were related to the processing degree of the silk source. Moreover, the properties of SS films seemed to be dominated by the primary structure and the presence of natural impurities in each extract. The results suggest that silk sources could be selected ad hoc to design SS materials with distinctive properties for specific applications.Three different silk sources were explore for sericin (SS) extraction and film formation. Features of each raw material, especially the degree of processing, have remarkable effects on the primary structure and the presence of nonprotein compounds in the sericin extract. As a result, sericin films exhibited distinctive properties that seemed to be correlated with the amount of natural impurities and the molecular properties of the SS extract obtained from each raw material.

Organic phase change materials (PCMs) represent an effective solution to manage intermittent energy sources as the solar thermal energy. This work aims at encapsulating docosane in organosilica shells and at dispersing the produced capsules in epoxy/carbon laminates to manufacture multifunctional structural composites for thermal energy storage (TES). Microcapsules of different sizes were prepared by hydrolysis-condensation of methyltriethoxysilane (MTES) in an oil-in-water emulsion. X-ray diffraction (XRD) highlighted the difference in the crystalline structure of pristine and microencapsulated docosane, and 13C solid-state nuclear magnetic resonance (NMR) evidenced the influence of microcapsules size on the shifts of the representative docosane signals, as a consequence of confinement effects, i.e., reduced chain mobility and interaction with the inner shell walls. A phase change enthalpy up to 143 J/g was determined via differential scanning calorimetry (DSC) on microcapsules, and tests at low scanning speed emphasized the differences in the crystallization behavior and allowed the calculation of the phase change activation energy of docosane, which increased upon encapsulation. Then, the possibility of embedding the microcapsules in an epoxy resin and in an epoxy/carbon laminate to produce a structural TES composite was investigated. The presence of microcapsules agglomerates and the poor capsule-epoxy adhesion, both evidenced by scanning electron microscopy (SEM), led to a decrease in the mechanical properties, as confirmed by three-point bending tests. Dynamic mechanical analysis (DMA) highlighted that the storage modulus decreased by 15% after docosane melting and that the glass transition temperature of the epoxy resin was not influenced by the PCM. The heat storage/release properties of the obtained laminates were proved through DSC and thermal camera imaging tests.

Barium Titanate (BaTiO3) is one of the most promising lead-free ferroelectric materials for the development of piezoelectric nanocomposites for nanogenerators and sensors. The miniaturization of electronic devices is pushing researchers to produce nanometric-sized particles to be embedded into flexible polymeric matrices. Here, we present the sol-gel preparation of crystalline BaTiO3 nanoparticles (NPs) obtained by reacting barium acetate (Ba(CH3COO)2) and titanium (IV) isopropoxide (Ti(OiPr)4). The reaction was performed both at ambient conditions and by a hydrothermal process carried on at 200 °C for times ranging from 2 to 8 h. Doped BaTiO3 nanoparticles were also produced by addition of Na, Ca, and Bi cations. The powders were annealed at 900 °C in order to improve NPs crystallinity and promote the cubic-to-tetragonal (c⟶t) phase transformation. The microstructural features of nanoparticles were investigated in dependence of both the hydrothermal reaction time and the presence of dopants. It is found that short hydrothermal treatment (2 h) can produce BaTiO3 spherical and more homogeneous nanoparticles with respect to longer hydrothermal treatments (4 h, 6 h, 8 h). These particles (2 h) are characterized by decreased dimension (approx. 120 nm), narrower size distribution and higher tetragonality (1.007) in comparison with particles prepared at ambient pressure (1.003). In addition, the short hydrothermal treatment (2 h) produces particles with tetragonality comparable to the one obtained after the longest process (8 h). Finally, dopants were found to affect to different extents both the c⟶t phase transformation and the crystallite sizes.

This study aims to demonstrate the remarkable features of graphene-based fillers, which are able to improve the protective performance of acrylic coatings. Furthermore, the joint application of a cataphoretic primer and a spray top coat, containing graphene and functionalized graphene oxide flakes, respectively, enables the deposition of a double-layer coating with high conductivity and abrasion resistance properties, capable of offering excellent corrosion resistance to the metal substrate. The surface morphology of the single- and double-layer coatings was investigated by optical and electron microscopies, analysing the defectiveness introduced in the polymer matrix due to the filler agglomeration. The behavior in aggressive environments was assessed by exposure of the samples in the salt spray chamber, evaluating the blister formation and the adhesion level of the coatings. Electrochemical impedance spectroscopy measurements were employed to study the corrosion protection properties of the coatings, whose conductivity and abrasion resistance features were analysed by conductivity assessment and scrub tests, respectively. The incorporation of graphene-based fillers in the cataphoretic primer improves the corrosion protection properties of the system, while the graphene flakes provide the top coat spray layer with high conductivity and excellent abrasion resistance features. Thus, this work demonstrates the possibility of employing different types of graphene-based fillers and deposition methods for the creation of multifunctional coatings.

Starch was plasticized with epoxidized soybean oil (ESO) modified by reaction with cinnamic acid (CA), and films were prepared using solvent casting from water/ethanol solutions. They exhibited good hydrophobicity, reduced water sensitivity, and showed the same transparency as glycerol-plasticized counterparts, but with less flexibility. Interestingly, modified ESO enhanced gelatinization and hindered retrogradation of the biopolymer. ESO was reacted with CA without the use of catalysts to obtain a β-hydroxyester; in order to optimize the synthesis process, different reaction conditions were explored, varying the stoichiometry and the heating cycles. Products were fully characterized by Fourier transform infrared (FTIR) spectroscopy, 1H and 13C nuclear magnetic resonance (NMR), and the different reactions following the opening of the oxirane ring were discussed. The properties of the novel starch-based films prepared with modified ESO highlight their use in food packaging, disposable devices, and agricultural mulching films.

The functional properties displayed by graphene oxide (GO)-polymer nanocomposites are strongly affected by the dispersion ability of GO sheets in the polymeric matrix, which can be largely improved by functionalization with organosilanes. The grafting to GO of organosilanes with the general formula RSi(OCH3)3 is generally explained by the condensation reactions of silanols with GO reactive groups. In this study, the influence of the organic group on the RSi(OCH3)3 grafting ability was analyzed in depth, taking into account the interactions of the R end chain group with GO oxidized groups. Model systems composed of commercial graphene oxide reacted with 3-aminopropyltrimethoxysilane (APTMS), 3-mercaptopropyltrimethoxysilane (MPTMS), and 3-methacryloxypropyltrimethoxysilane, (MaPTMS), respectively, were characterized by natural abundance 13C, 15N and 29Si solid state nuclear magnetic resonance (NMR), x-ray diffraction (XRD), and electron spin resonance (ESR). The silane organic tail significantly impacts the grafting, both in terms of the degree of functionalization and direct interaction with GO reactive sites. Both the NMR and XRD proved that this is particularly relevant for APTMS and to a lower extent for MPTMS. Moreover, the epoxy functional groups on the GO sheets appeared to be the preferential anchoring sites for the silane condensation reaction. The characterization approach was applied to the GO samples prepared by the nitric acid etching of graphene and functionalized with the same organosilanes, which were used as a filler in acrylic coatings obtained by cataphoresis, making it possible to correlate the structural properties and the corrosion protection ability of the layers.