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This study explores a novel approach to obtaining 3D printed strain sensors, focusing on how changing the printing conditions can produce a different piezoresistive response. Acrylonitrile butadiene styrene (ABS) filled with different weight concentrations of carbon nanotubes (CNTs) was printed in the form of dog bones via fused filament fabrication (FFF) using two different raster angles (0–90°). Scanning electron microscopy (SEM) and atomic force microscopy (AFM) in TUNA mode (TUNA-AFM) were used to study the morphological features and the electrical properties of the 3D printed samples. Tensile tests revealed that sensitivity, measured by the gauge factor (G.F.), decreased with increasing filler content for both raster angles. Notably, the 90° orientation consistently showed higher sensitivity than the 0° orientation for the same filler concentration. Creep and fatigue tests identified permanent damage through residual electrical resistance values. Additionally, a cross-shaped sensor was designed to measure two-dimensional deformations simultaneously, which is applicable in the robotic field. This sensor can monitor small and large deformations in perpendicular directions by tracking electrical resistance variations in its arms, significantly expanding its measuring range. [ABSTRACT FROM AUTHOR]

The current study analyzes the possibility of determining the drug location in electrospun polymeric matrices and forecasting the release kinetics of drug delivery systems. Electrospun membranes made of polycaprolactone (PCL) loaded with dacarbazine (the drug of choice for the treatment of melanoma) and with AuM1 (a promising synthetic Au‐based complex recently proposed for antitumoral treatments) are successfully prepared. Atomic force microscopy (AFM) analysis is performed on various membranes, highlighting the relevance of investigating the three‐dimensional topology of the membranes for understanding the release kinetic. The produced mats are similar for all membranes, but significant differences in the microscopic roughness wall between the systems loaded with AuM1 and dacarbazine are observed. For AuM1, which has a low affinity with the PCL matrix, the complex aggregates on the nanofibers' external walls, consequently increasing the roughness and causing a high burst in the first hours of release. On the other hand, dacarbazine is successfully included in the bulk core of the PCL nanofibers. Thus, the release kinetics is diffusive and well described by the Fick model. [ABSTRACT FROM AUTHOR]

Additive manufacturing (AM) is an innovative production process that allows for designing objects with self‐responsive properties exploiting the potentialities of nanotechnologies. In this context, acrylonitrile butadiene styrene (ABS) filled with multi‐walled carbon nanotubes (MWCNT) is printed via fusion deposition modeling (FDM) by setting two different printing directions, 0° and 90°. The investigation of the electrical properties of 3D printed parts demonstrates that the printing direction affects the pathway of electrical current flow and, consequently, the heating performance. A suitable setting of the raster angle allows the alignment of the carbon nanotubes along the printing direction. This alignment, verified through morphological investigations, strongly influences the heating properties due to the Joule effect. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of polyethylene glycol monomethyl ether methacrylate (PEGMA) based copolymers incorporating three different percentages (2.5 wt%, 5.0 wt%, and 7.8 wt%) of urea‐N‐2‐amino‐4‐hydroxy‐6‐methylpyrimidine‐N'‐(hexametylen‐n‐carboxyethyl methacrylate) (HEMA‐UPy) are reported. Nuclear magnetic resonance (NMR) and infrared spectroscopy (IR) confirm the synthesis procedure. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) are employed to evaluate the thermal properties of the samples. DSC measurements evidence a slight increase in glass transition temperature (Tg), a consistent increase in crystallization and melting temperatures (Tc and Tm), and a reduction in the crystallization degree (Xc) with increasing the amount of HEMA‐UPy moiety. Dynamic mechanical analysis (DMA) is carried out at different values of temperature and oscillation frequency. It highlights the ability of the healed copolymer to recover the pristine values of storage modulus. The healing efficiency depends on the temperature history of the sample. For the sample healed at room temperature, the value of healing efficiency is 64%. DMA tests performed at higher temperatures, after some permanence at room temperature, evidence higher values in the healing efficiency. This demonstrates that the higher value of the temperature employed during DMA tests determines greater mobility of the chains causing an enhancement in the healing efficiency. [ABSTRACT FROM AUTHOR]

Polymer-matrix composites containing conductive nanoparticles are a potential means for achieving an appealing combination of multifunctional properties for their use as structural parts in the aerospace field. Carbon nanofibers (CNFs) have been being looked forward to as the next generation of new and avant-garde aircraft structures because they are exceptionally coveted competitor materials to replace traditional metal components for lightning strike protection. In this regard, nanocomposites at low concentration of CNFs ranging from 0.05% up to 2% by wt to impart electron conduction in tetrafunctional epoxy resin have been prepared and characterized. The aim of this work concerns the use of Tunneling AFM (TUNA) as revolutionary tool able to correlate the electrical current map with the correspondent local morphology of CNF/resins. TUNA technique has proven to play a leading role in the identification of current paths and electrical interconnections, even without altering the morphology with usual treatments employed to create electrical contacts to the ground. Summing up, the good electrical performance together with the high mechanical properties due to a conductive cross-linked network of CNFs inside the resin demonstrate a charming applicative potential for the formulated nanocomposites as structural materials capable to provide a safe conductive path on the exterior skin, preventing serious damage to the aircraft.

Functionalized multi-wall carbon nanotubes (MWCNTs) have been embedded in a rubber-toughened epoxy formulation in order to explore the possibility to impart an auto-repair function to the epoxy matrix. The nanofiller has been covalently functionalized with hydrogen bonding moieties able to act as donor and acceptor of hydrogen bondings. Healing efficiencies have been evaluated for nano charged epoxy formulations at a loading of 0.5% wt/wt of functionalized MWCNTs bearing barbituric acid and thymine-based ligands. For both the performed functionalizations, a self-healing efficiency higher than 50% has been found. Dynamic Mechanical Analysis (DMA) highlights that the inclusion of nanofiller increases the storage moduli. Furthermore, DMA analysis evidences the presence of a phase characterized by a greater mobility of the epoxy chains, which promotes the activation of self-healing mechanisms.

Epoxy nanocomposites fulfill tight and compelling industrial requirements in the field of structural material for aeronautical applications. In this paper the development and characterization of nanocomposites obtained by filling tetrafunctional epoxy resin (tetraglycidyl methylene dianiline cured with the aromatic diamine 4,4’-diaminodiphenylsulfone, named T20BD) with carbon nanofibers (CNF) is discussed. A filler amount ranging from 0.05% to 2%wt is considered. The DC volume conductivity and the dielectric characteristics (ϵ’) of the nanocomposites in the frequency range 100Hz-1MHz are analyzed and compared with those of the pure resin. Atomic force microscopy, mapping the local topography by means of tunneling effect, is used for recording the electrical percolation path for nanocomposites. In particular, the case 1.3wt% of CNF filled nanocomposites that exhibits a stable behavior of the conductivity in the full investigated frequency range, is here reported. The developed filled epoxy used in carbon fiber reinforced composites, shows enhanced electrical properties leading to better electromagnetic (EM) performances in EM coatings, EM shields and filters or radar absorber materials (RAMs).