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Biomaterials are engineered to develop an interaction with living cells for therapeutic and diagnostic purposes. The last decade reported a tremendously rising shift in the requirement for miniaturized biomedical implants exhibiting high precision and comprising various biomaterials such as non-biodegradable titanium (Ti) alloys and biodegradable magnesium (Mg) alloys. The excellent mechanical properties and lightweight characteristics of Mg AZ91D alloy make it an emerging material for biomedical applications. In this regard, micro-electric discharge machining (µEDM) is an excellent method that can be used to make micro-components with high dimensional accuracy. In the present research, attempts were made to improve the µEDM capabilities by using cryogenically-treated copper (CTCTE) and brass tool electrodes (CTBTE) amid machining of biodegradable Mg AZ91D alloy, followed by their comparison with a pair of untreated copper (UCTE) and brass tool electrodes (UBTE) in terms of minimum machining-time and dimensional-irregularity. To investigate the possible modification on the surfaces achieved with minimum machining-time and dimensional-irregularity, the morphology, chemistry, micro-hardness, corrosion resistance, topography, and wettability of these surfaces were further examined. The surface produced by CTCTE exhibited the minimum surface micro-cracks and craters, acceptable recast layer thickness (2.6 µm), 17.45% improved micro-hardness, satisfactory corrosion resistance, adequate surface roughness (Ra: 1.08 µm), and suitable hydrophobic behavior (contact angle: 119°), confirming improved biodegradation rate. Additionally, a comparative analysis among the tool electrodes revealed that cryogenically-treated tool electrodes outperformed the untreated ones. CTCTE-induced modification on the Mg AZ91D alloy surface suggests its suitability in biodegradable medical implant applications.

Self-healing polymers render their life cycle more sustainable by recovering their properties upon healing. Intrinsic self-healing polymers can be recycled, which further reduces waste production. Yet, despite these intrinsic benefits, several sustainability issues remain largely neglected, including the use of fossil-derived materials, hazardous chemicals, and the material management at the end of its life. Herein we report a series of castor oil-based self-healing elastomers that account for these challenges and show improved mechanical and self-healing capabilities compared to the other bio-based self-healing materials. Castor oil was functionalized using a simple, one-pot, solventless synthesis from renewable resources and crosslinked by Diels-Alder cycloaddition. They can be reprocessed and recycled, or hydrolytically degraded at the end of their service life. The mechanical properties of the materials can be tuned (Young’s modulus 0.5-20 MPa), with a fracture strain of up to 487%. A fracture strain of 100% could already be recovered after just 60 seconds at room temperature, and 75% of the mechanical properties after just 24 h. By taking advantage of these properties, a soft pneumatic gripper has been developed, capable of healing autonomously which is fully recyclable and degradable. Hence, we provide a sustainable alternative for soft-robotics applications and for self-healing elastomers in general.

Electrodeposition from an environmentally friendly iron sulfate electrolyte with citric acid as carbon source has gained attention recently, because of excellent mechanical properties of the resulting Fe–C coatings with intentionally codeposited high-carbon concentrations. While being very attractive as protective coatings and sustainable alternatives for hard chrome coatings, comprehensive understanding of the coatings' chemical constitution including the type and location of carbon-containing phases is still lacking. The amount of codeposited carbon of up to about 0.8 wt.% significantly exceeds the solubility of carbon in ferrite, although carbon-free ferrite is the only unambiguously reported phase in as-deposited Fe–C coatings so far. In the present work, time-of-flight secondary ion mass spectrometry, X-ray photoelectron spectroscopy, and soft X-ray emission spectroscopy have been applied to identify the carbon-containing phases, which are present as minor secondary phases in the coatings but are known to have an important influence on the coatings' properties. Three carbon-containing phases could be distinguished, homogeneously distributed in the nanocrystalline ferrite base material. Iron acetates, amorphous carbon, and carbides were found in both as-deposited and annealed Fe–C coatings up to 300°C, but their fraction changes during postdeposition annealing.

The non-degradable metallic implants, such as bone screws, often act as the source of dysfunction and harmful corrosion products in the aqueous environment inside the human body. Many of these implants are fixed either temporarily or permanently into the human body, and therefore, both need to match tight tolerances with a remarkably finished surface to eradicate burrs or striations. In this regard, the new generation of degradable magnesium (Mg) alloy implants with excellent osseointegration and low elasticity (like that of human bone), minimizing stress shielding, have been identified as potential candidates to challenge surgical procedures reintervention. However, the biological response of an implant toward the cells in vivo can be predominantly regulated by modifying the surface chemistry, morphology, and corrosion characteristics. Powder or abrasive-mixed-micro-electric discharge machining (A-M-µ-EDM) is gaining attention for executing precision machining and achieving a simultaneous surface modification on micro-manufactured surfaces, suitable for clinical applications. Therefore, the present research aimed at improving the surface characteristics of Mg AZ31B alloy via an augmented performance of A-M-µ-EDM by adopting copper and brass-micro-electrodes (C-µ-E and B-µ-E) in association with distinct abrasive particle concentrations (APCs: 0, 1.5, 3, 4.5, and 6 g/l) of bioactive zinc abrasives. To enhance the A-M-µ-EDM capabilities, the experiments were designed with a one-variable-at-a-time (OVAT) strategy, and the trial runs were conducted using different combinations of µ-electrodes and APCs. The superior performance of A-M-µ-EDM was noticed with the fusion of C-µ-E and 3 g/l APC in terms of minimum machining time (MT) and dimensional deviation (DD). The additional outcomes of this work reported favorable improvements in surface morphology, chemistry, topography, wettability, microhardness, and corrosion resistance on the A-M-µ-EDMed sample of interest.

The high-temperature transformations and crystallization of K-based inorganic polymers made from FeO-SiO2 and FeO-SiO2-Al2O3 iron-rich model slags were investigated, with particular focus on the effect of the Al/K and Si/K molar ratios. Upon firing to 1100 °C, the main crystalline phases were hematite and (iron) leucite. Addition of corundum decreases the crystallization rate of leucite. Increasing the Al/K molar ratio increased the thermal stability due to the substitution of Al3+ for Fe3+ in leucite. The Si/K molar ratio impacted the crystallization of leucite. Upon firing to 1100 °C and 1350 °C there was a linear correlation between the amount of leucite and the Si/K molar ratio. Higher Si/K molar ratio resulted in ceramics with higher glass content and lower thermal stability. Thus, the phase assemblage can be adjusted by changing the amount of activator.

Peptide-based hydrogels represent promising systems for the sustained release of different types of drugs, ranging from small molecules to biologicals. Aiming at subcutaneous injection, which is a desirable parenteral administration route, especially for biologicals, we herein focus on physically crosslinked systems possessing thixotropic behaviour. The purpose of this study was to evaluate the in vitro and in vivo properties of hydrogels based on the amphipathic hexapeptide H-FQFQFK-NH2, which served as the lead sequence. Upon doubling the length of this peptide, the dodecapeptide H-FQFQFKFQFQFK-NH2 gave a significant improvement in terms of hydrogel’s in vivo stability post-injection, as monitored by nuclear SPECT/CT imaging. This increased hydrogel stability also led to a more prolonged in vivo release of encapsulated peptide cargoes. Even though no direct link with the mechanical properties of the hydrogels before injection can be made, an important effect of the subcutaneous medium was noticed in post invivo injection measurements. The results were validated for a therapeutically relevant analgesic peptide using the hot-plate test as an acute pain model. Gratifyingly, it was confirmed that elongation of the hydrogelator sequence induced more extended antinociceptive effects. Altogether, this simple structural modification of the hydrogelating peptide could provide a basis for reaching longer durations of action upon use of these soft biomaterials.

This work investigated the chemical and electrochemical mechanisms of localised corrosion triggered by CaS·xMgO·yAl2O3·TiN complex inclusions in high strength low alloy steel (HSLAS) under a simulated marine environment. Special focus was given to the role of the TiN portion of the inclusion on the initiation and growth of the corrosion pits. The thermodynamic process of pitting initiation was investigated by Gibbs free energy, Pourbaix diagram and first principle calculation. Localised corrosion is mainly induced by inclusions and triggered by dissolution of adjacent distorted matrix. Chemical dissolution of CaS portion in CaS·xMgO·yAl2O3·TiN complex inclusion creates an acidic aggressive environment that accelerates the further dissolution of inclusion and matrix. Galvanic coupling effect between TiN inclusion and matrix is directly verified. TiN covered with a TiO2 film acts as the cathodic phase in galvanic corrosion, although it has a lower Volta potential than the matrix. This is an unusual correlation with the scanning Kelvin probe force microscopy result, which has been explained for this special system.

Superparamagnetic iron oxide nanoparticles are a promising material in nanomedicine, especially for generating magnetically controlled drug delivery systems. We developed an innovative ureidopyrimidinone (UPy) coating based on supramolecular hydrogen bonding units. The synthesized nanoparticles possess a positively charged surface with a hydrodynamic diameter of 177 nm at pH 7 and magnetization of 31 emu g-1. The system has the potential to be modified by drugs or bioactive molecules altered with UPy units.

The variability in the shapes and sizes of objects presents a significant challenge for two-finger robotic grippers when it comes to manipulating them. Based on the chemistry of vitrimers (a new class of polymer materials that have dynamic covalent bonds, which allow them to reversibly change their mechanical properties under specific conditions), we present two designs as 3D-printed shape memory polymer-based shape-adaptive fingertips (SMP-SAF). The fingertips have two main properties needed for an effective grasping. First, the ability to adapt their shape to different objects. Second, exhibiting variable rigidity, to lock and retain this new shape without the need for any continuous external triggering system. Our two design strategies are: 1) A curved part, which is suitable for grasping delicate and fragile objects. In this mode and prior to gripping, the SMP-SAFs are straightened by the force of the parallel gripper and are adapted to the object by shape memory activation. 2) A straight part that takes on the form of the objects by contact force with them. This mode is better suited for gripping hard bodies and provides a more straightforward shape programming process. The SMP-SAFs can be programmed by heating them up above glass transition temperature (54°C) via Joule-effect of the integrated electrically conductive wire or by using a heat gun, followed by reshaping by the external forces (without human intervention), and subsequently fixing the new shape upon cooling. As the shape programming process is time-consuming, this technique suits adaptive sorting lines where the variety of objects is not changed from grasp to grasp, but from batch to batch.

The molecular dynamics of the reversible network 4F230-2M230 were studied systematically by dielectric relaxation spectroscopy (DRS) at frequencies between 10–1 and 107 Hz under both isothermal and non-isothermal conditions, focusing on the cooperative segmental dynamics as sensed by the dielectric α-relaxation. This reversible network is based on the furan–maleimide Diels–Alder reaction of a 4-functional furan-functionalized Jeffamine coupled with a 2-functional maleimide. Different strategies for extracting a “dielectric” glass transition temperature (Tg) were employed and compared. First, relaxation times τα were derived by conventional Havriliak–Negami fits of dielectric spectra and then fitted to the Vogel–Fulcher–Tammann (VFT) equation, which yields the dynamic Tg of partially cured samples (approach I). Alternatively, the thermal glass transition temperature was derived from the dielectric spectra ε′(f, T) using a fine structure analysis by bivariate differential sampling. Both the dynamic and thermal Tgs revealed an excellent agreement, confirming the stability of the VFT fits as well as the equivalence of both quantities as usually expected for bulk glass-forming materials. Two attempts were made to find a unique set of VFT parameters based on a global fit considering DRS spectra from partially cured samples during heating from −120 to 100 °C. Via a first procedure (approach II), a unique set of VFT parameters EV and τ∞ was obtained that well describes the relaxation times during non-isothermal cure at temperatures where the effects of ongoing cure kinetics can be neglected. To overcome this restriction, a refined approach III was developed that includes the earlier reported kinetic model for the DA reaction and allows accurate predictions for the relaxation time evolution during both isothermal and non-isothermal cure experiments. Based on this unique description, a new technique for continuous cure monitoring was proposed and tested. This technique allows us to compute in real-time dynamic Tg from the relaxation time τα at any stage of the isothermal or non-isothermal cure process using two unique VFT parameters from the global fit procedure. This approach might stimulate new applications of DRS-based cure monitoring.

Dielectric elastomer actuators rely on Coulomb forces for their actuation. They are promising candidates when it comes to the manufacture of electrically driven soft and lightweight robotic devices, which can undergo large movement. However, their commercial availability and hence their technological relevance are still rather limited due to several reasons: in-depth material knowhow in terms of electrical and mechanical behavior required; materials have to be available in thin sheets; complicated and error prone fabrication; limited design freedom. In order to change this, this paper presents a soft dielectric actuator fully produced by fused filament fabrication. Additive manufacturing with conventional fused filament fabrication machines offers the potential for the production of personalized dielectric actuators which are easily accessible and comparably cheap. The only requirement is a fused filament fabrication printer with multi-material capability. Focusing on a mass customization of the 3D printed actuators, exclusively commercially available devices and filaments without any modifications are used. In particular, the 3D printed prototypes are characterized in terms of the maximum displacement depending on the electrode printing direction. As a showcase example, a soft dielectric gripper made of two 3D printed actuators is developed. Comparable with other dielectric elastomer actuators, a maximum displacement of 42% is reached.

water uptake in organic coatings. To this aim, we start from a physical model, where not only Fickian diffusion of water is taken into account but also the adsorption/desorption reaction of water on the polymer matrix. Starting from a number of important coating properties and crucial model parameters, derived from gravimetric and Fourier transform infrared (FTIR) measurements as the model input, the local water concentration over the coating thickness as a function of time is modelled for a polyethylene glycol diacrylate (PEGDA) coating. The modelled water concentration is then used to calculate virtual capacitance values which are evaluated against experimental capacitance values extracted from impedance measurements. The constraints of the FEM model and ORPEIS experiments and the discrepancies between them are critically discussed in order to carry out a meaningful model validation, eventually leading to model improvements.

Carbon nanofibers (CNFs) is a typical electrical loss material with strong permittivity that has been widely used in the field of electromagnetic shielding, attenuation, and reception. However, studies have demonstrated that the unstable anisotropic EM behavior exhibited by CNFs in the terahertz domain hinders its application in the tremendously high frequency domain. In this study, ZnO is used to perform surface modification of CNFs based on the sputtering method, which effectively eliminate the anisotropic EM behavior of CNFs at different irradiation angles in the sub-terahertz band. ZnO coated the surface of fiber wall comprehensively in the form of nano-scale. The results show that after the surface modification, the composite sample exhibits a stable isotropic EM response in the sub-terahertz band of 500-750 GHz. Also, in the frequency range of 551-563 GHz (bandwidth: 12 GHz), ZnO not only acts as a stabilizer, but also enhances the absorption performance of the original CNFs by 6%, which is up to 92%. In the frequency range of 660-690 GHz (bandwidth: 30 GHz), the composite sample and the pure CNFs sample have similar wave absorption performance with about 75%, the maximum difference is less than 5%, and the minimum is about 2.6%.

Materials and corrosion (2022). doi:10.1002/maco.202213140, Published by Wiley-VCH, Weinheim [u.a.]

Self-healing soft robots show enormous potential to recover functional performance after healing the damages. However, healing in these systems is limited by the recontact of the fracture surfaces. This paper presents for the first time a shape memory alloy (SMA) wire-reinforced soft bending actuator made out of a castor oil-based self-healing polymer, with the incorporated ability to recover from large incisions via shape memory assisted healing. The integrated SMA wires serve three major purposes; (i) Large incisions are closed by contraction of the current-activated SMA wires that are integrated into the chamber. These pull the fracture surfaces into contact, enabling the healing. (ii) The heat generated during the activation of the SMA wires is synergistically exploited for accelerating the healing. (iii) Lastly, during pneumatic actuation, the wires constrain radial expansion and one-side longitudinal extension of the soft chamber, effectuating the desired actuator bending motion. This novel approach of healing is studied via mechanical and ultrasound tests on the specimen level, as well as via bending characterization of the pneumatic robot in multiple damage healing cycles. This technology allows soft robots to become more independent in terms of their self-healing capabilities from human intervention.

The thermophysical properties, mechanical behavior, and healing performance of Diels–Alder-based polymer networks can be tuned widely by changing the molar mass, functionality, and stoichiometric ratio of the multifunctional diene (e.g., furan) and dienophile (e.g., maleimide) monomers. Blending furan-functionalized monomers with a high and low molar mass opens a new dimension in tuning the properties of the resulting reversible polymer network blends (RPNBs), containing different ratios of elastomeric and thermoset phases, with low and high crosslink densities and glass transitions below and above room temperature, respectively. Increasing the thermoset content up to 20 wt % raises the gel transition temperature (Tgel), relaxation time (τ), rubbery plateau modulus, ultimate stress, and Young’s modulus of the stiffened elastomers, while the strain at fracture and self-healing efficiency remained mostly unchanged. Conversely, the addition of up to 20 wt % of the elastomer phase drastically toughens the thermosets because of stress dissipation, which can suppress the stress concentration in the phase-separated network blends. The blends showed higher stress and strain at break while retaining similar Young’s moduli. The toughness increases up to an order of magnitude at 50 wt %, compared to the pure thermoset. The phase-separated morphologies were evidenced by the presence of the Tg’s of the pure networks in DSC and DMA.

Vascular in situ tissue engineering encompasses a single-step approach with a wide adaptive potential and true off-the-shelf availability for vascular grafts. However, a synchronized balance between breakdown of the scaffold material and neo-tissue formation is essential. Chronic kidney disease (CKD) may influence this balance, lowering the usability of these grafts for vascular access in end-stage CKD patients on dialysis. We aimed to investigate the effects of CKD on in vivo scaffold breakdown and tissue formation in grafts made of electrospun, modular, supramolecular polycarbonate with ureido-pyrimidinone moieties (PC-UPy). We implanted PC-UPy aortic interposition grafts (n = 40) in a rat 5/6th nephrectomy model that mimics systemic conditions in human CKD patients. We studied patency, mechanical stability, extracellular matrix (ECM) components, total cellularity, vascular tissue formation, and vascular calcification in CKD and healthy rats at 2, 4, 8, and 12 weeks post-implantation. Our study shows successful in vivo application of a slow-degrading small-diameter vascular graft that supports adequate in situ vascular tissue formation. Despite systemic inflammation associated with CKD, no influence of CKD on patency (Sham: 95% vs CKD: 100%), mechanical stability, ECM formation (Sirius red+, Sham 16.5% vs CKD 25.0%–p:0.83), tissue composition, and immune cell infiltration was found. We did find a limited increase in vascular calcification at 12 weeks (Sham 0.08% vs CKD 0.80%—p:0.02) in grafts implanted in CKD animals. However, this was not associated with increased stiffness in the explants. Our findings suggest that disease-specific graft design may not be necessary for use in CKD patients on dialysis.

The combination of different polymers in the form of blended plastics has been used in the plastic industry for a long time. Nevertheless, analyses of microplastics (MPs) have been mainly limited to the study of particles made of single-type polymers. Accordingly, two members of the Polyolefins (POs) family, i.e., Polypropylene (PP) and Low-density Polyethylene (LDPE) are blended and extensively studied in this work due to their applications in industry as well as abundance in the environment. It is shown that 2-D Raman mapping only provides information about the surface of blended MPs (B-MPs). While complimentary 3-D volume analysis is needed to fully understand the presence of various polymers in such complex samples. Therefore, 3-D Raman mapping is applied to visualize the morphology of the distribution of polymers within the B-MPs together with the quantitative estimation of their concentrations. A parameter defined as the concentration estimate error (CEE) evaluates the precision of the quantitative analysis. Furthermore, the impact of four excitation wavelengths 405, 532, 633, and 785 nm is investigated on the obtained results. Finally, the application of a line-shaped laser beam profile (line-focus) is introduced for reducing the measurement time from 56 to 2 h.

Fungi-mediated self-healing concrete is a novel approach that promotes the precipitation of calcium carbonate (CaCO3) on fungal hyphae to heal the cracks in concrete. In this study, we set out to explore the potential of fungal species isolated from a limestone cave by investigating their ability to precipitate CaCO3 and to survive and grow in conditions relevant to concrete. Isolated strains belonging to the genera Botryotrichum sp., Trichoderma sp. and Mortierella sp. proved to be promising candidates for fungi-mediated self-healing concrete attributed to their growth properties and CaCO3 precipitation capabilities in the presence of cement.

Effect of bisulfite (HSO3-) on the stress corrosion cracking (SCC) behavior of 7050-T7451 aluminum alloy in the thin electrolyte layer environment in the presence of Cl- is investigated. Addition of HSO3- inhibits the corrosion initiation but promotes the corrosion propagation and hydrogen uptake. With a quantitative calculation, the HSO3- is demonstrated to significantly facilitate the synergistic effect between stress, corrosion, and hydrogen during the in-situ tensile test, resulting in the change of the SCC controlling step from corrosion-induced hydrogen to mechanical-electrochemical-hydrogen interactions. The buffer effect of HSO3- plays a dominant role in the HSO3--induced acceleration of the SCC degradation.

Magnetorheological (MR) elastomers are a class of stimuli-responsive materials of which the damping and stiffness can be reversibly tailored by applying magnetic fields. However, concerns such as fatigue damage, insufficient MR efficiencies with low loadings of magnetic particles or highly crosslinked elastomers, and lack of reprocessability remain unaddressed for conventional MR elastomers. To this end, a series of self-healing MR elastomers (SHMRE) were prepared based on thermoreversible Diels–Alder covalent crosslinks. The application of magnetic pulses yielded pre-aligned magnetic particles chains within the curing matrix which strongly influenced the SHMRE rheological properties. The resulting composites do not only exhibit a large MR effect but also efficient self-healing properties at room temperature. We found that the particle loading and the field-induced orientation of the aggregates affect the magnitude of the MR response, the mechanical strength and the healing efficiency. In addition, the MR response is also strongly influenced by the temperature. With a temperature increase from room temperature to 70 °C, a change in the MR response from 90% to 462% is observed while the SHMRE retain a solid viscoelastic state at 50 wt% particles loading. Interestingly, the thermoreversible features of the synthesized networks also allow potential reprocessability of SHMRE when heating these systems above the gel transition temperature (89 °C–90 °C). The final low viscous state makes it possible for the magnetic particles to be potentially restructured as chains by applying a magnetic field, which are retained upon cooling when the solid network state is recovered. The proposed SHMRE systems are shown to be a highly efficient and reprocessable solution to substitute classical MR elastomers in a wider context of generalized MR materials.

Interest in deep eutectic solvents (DESs), particularly for electrochemical applications, has boomed in the past decade because they are more versatile than conventional electrolyte solutions and are low cost, renewable, and non-toxic. The molecular scale lateral nanostructures as a function of potential at the solid–liquid interface—critical design parameters for the use of DESs as electrochemical solvents—are yet to be revealed. In this work, in situ amplitude modulated atomic force microscopy complemented by molecular dynamics simulations is used to probe the Stern and near-surface layers of the archetypal and by far most studied DES, 1:2 choline chloride:urea (reline), at the highly orientated pyrolytic graphite surface as a function of potential, to reveal highly ordered lateral nanostructures with unprecedented molecular resolution. This detail allows identification of choline, chloride, and urea in the Stern layer on graphite, and in some cases their orientations. Images obtained after the potential isswitched from negative to positive show the dynamics of the Stern layer response, revealing that several minutes are required to reach equilibrium. These results provide valuable insight into the nanostructure and dynamics of DESs at the solid–liquid interface, with implications for the rational design of DESs for interfacial applications.

Funding Information: This work was supported by the European Union Horizon 2020 research programme under MSCA COFUND grant agreement 101034352 with co-funding from the VUB-Industrial Research Fund: X-ray tomography was also supported by the Academy of Finland via RAMI infrastructure project (#293109). Publisher Copyright: © 2023 by the authors. As we know, 3DPC is printed layer by layer compared with mold-casting conventional concrete. Pore structure and layer-to-layer interface are two main aspects of the internal structure for 3DPC, which decide 3DPC’s mechanical performance. The layer-to-layer interface caused by printing is specific to 3DPC. The emphasis of this study lies in the layer-to-layer interfaces of 3DPC. The first aim of this study is to quantify the characteristics of the layer-to-layer interface and therefore characterize different aspects of the interfaces. The second aim of this study is to explore how the internal structure of printed concrete influences the mechanical performance of 3DPC. This research set out to design a series of experimental comparisons between 3DPC and casted concrete with the same compositions. Mechanical tests, i.e., compressive stress, ultrasonic Pulse Velocity test, flexural tension, and tension splitting, as well as the Ultrasonic Pulse Velocity test, were performed to check the mechanical performance of3DPC. Contrary to what has often been expected, the mechanical test results showed the printed concrete has a quality not worse than casted concrete with the same recipe. Meanwhile, the X-ray computed tomography (X-CT) is used to characterize the internal structure, pore shapes, and interfaces of 3DPC. First, the investigation revealed that the lower total porosity and fewer big voids could be the fundamental causes meaning 3DPC has a better mechanical performance than casted concrete. Second, the statistics based on aspect ratio show that the distribution curves follow similar trends, regardless of the printed or casted concrete. Third, this study quantified the depth of the different interfaces for 3DPC. The results suggest that the porosity in an interface varies in a range. The author’s pioneer work has contributed to our present understanding of the interfaces of 3DPC.

The statistics analysis shows that the distribution curves of pore shapes follow similar trends, regardless of the printed concrete or casted concrete. The bigger voids with an equivalent diameter of more than 80 μm for casted concrete are more “equant” compared to printed concrete

In this work, the corrosion susceptibility of powder coated Al6060 alloys with increasing Cu and Zn content is evaluated in a benchmark test. Although higher Cu and Zn limits would enable the industry to increase the use of end-of-life scrap and thus produce eco-friendlier aluminium profiles, such alloys are often disregarded due to concerns of corrosion, especially filiform corrosion. Our results suggest that this concern is ungrounded as long as typical quality specifications for the pre-treatment and coating process are followed and the alloy composition is kept within the limits of the European norm AW6060. Furthermore, we point out that the variation of the results due to processing at different coating production lines is larger than the difference between alloys of different Cu and Zn contents.

The effect of hot stamping on the corrosion properties of boron-manganese 22MnB5 steel coated with hot-dip aluminum-silicon was evaluated under severe conditions by a continuous salt spray test (SST). The corrosion mechanism changed from localized to generalized, as cathodic precipitates were not present after hot stamping. Intrinsic defects in press-hardened steel samples were the reason for severe damage in both metallic coating and steel substrate under SST conditions. The red rust formed at the top surface, characterized as different iron-based compounds, is due to both the iron diffusion from the steel substrate toward the surface and the corrosion of the steel substrate.

Dynamicity plays a central role in biological systems such as in the cellular microenvironment. Here, the affinity and dynamics of different guest molecules in a transient supramolecular polymer hydrogel system, i.e. the host network, are investigated. The hydrogel system consists of bifunctional ureido-pyrimidinone (UPy) poly(ethylene glycol) polymers. A monofunctional complementary UPy guest is introduced, designed to interact with the host network based on UPy-UPy interactions. Furthermore, two other guest molecules are synthesized, being cholesterol and dodecyl (c12) guests; both designed to interact with the host network via hydrophobic interactions. At the nanoscale in solution, differences in morphology of the guest molecules were observed. The UPy-guest molecule formed fibers, and the cholesterol and c12 guests formed aggregates. Furthermore, cellular internalization of fluorescent guest molecules was studied. No cellular uptake of the UPy-cy5 guest was observed, whereas the cholesterol-cy5 guest showed membrane binding and cellular uptake. Also the c12-cy5 guest showed cellular uptake. Formulation of the guest molecules into the UPy hydrogel system was done to study the guest-host affinity. No changes in mechanical properties as measured with rheology were found upon guest-hydrogel formulation. Fluorescence recovery after photobleaching showed the diffusive properties of the cy5-functionalized guests throughout the host network. The c12 guest displayed a relatively fast mobility, the UPy guest displayed a decrease in mobility, and the cholesterol-guest remained relatively stable in the host network with little mobility. This demonstrates the tunable dynamic differences of affinity-based interaction between guest molecules and the host network. Interestingly, the cholesterol guest is internalized in cells and is robustly incorporated in the hydrogel network, while the UPy guest is not taken up by cells but shows an affinity to the hydrogel network. These results show the importance of guest-hydrogel affinity for future drug release. However, if modified with cholesterol these guests, or future drugs, will be taken up by cells; if modified with a UPy unit this does not occur. In this way both the drug-hydrogel interaction and the cell internalization behavior can be tuned. Regulating the host-guest dynamics in transient hydrogels opens the door to various drug delivery purposes and tissue engineering.

Vapor-phase film deposition of metal-organic frameworks (MOFs) would facilitate the integration of these materials into electronic devices. We studied the vapor-phase layer-by-layer deposition of zeolitic imidazolate framework 8 (ZIF-8) by consecutive, self-saturating reactions of diethyl zinc, water, and 2-methylimidazole on a substrate. Two approaches were compared: (1) Direct ZIF-8 "molecular layer deposition" (MLD), which enables a nanometer-resolution thickness control and employs only self-saturating reactions, resulting in smooth films that are crystalline as deposited, and (2) two-step ZIF-8 MLD, in which crystallization occurs during a postdeposition treatment with additional linker vapor. The latter approach resulted in a reduced deposition time and an improved MOF quality, i.e., increased crystallinity and probe molecule uptake, although the smoothness and thickness control were partially lost. Both approaches were developed in a modified atomic layer deposition reactor to ensure cleanroom compatibility.

Acrylate-endcapped urethane-based precursors constituting a poly(D,L-lactide)/poly(ε-caprolactone) (PDLLA/PCL) random copolymer backbone are synthesized with linear and star-shaped architectures and various molar masses. It is shown that the glass transition and thus the actuation temperature could be tuned by varying the monomer content (0–8 wt% ε-caprolactone, T g,crosslinked = 10—42 °C) in the polymers. The resulting polymers are analyzed for their physico-chemical properties and viscoelastic behavior (G′ max = 9.6–750 kPa). The obtained polymers are subsequently crosslinked and their shape-memory properties are found to be excellent (R r = 88–100%, R f = 78–99.5%). Moreover, their potential toward processing via various additive manufacturing techniques (digital light processing, two-photon polymerization and direct powder extrusion) is evidenced with retention of their shape-memory effect. Additionally, all polymers are found to be biocompatible in direct contact in vitro cell assays using primary human foreskin fibroblasts (HFFs) through MTS assay (up to ≈100% metabolic activity relative to TCP) and live/dead staining (>70% viability).

Benzene-1,3,5-tricarboxamide (BTA) glyco-monomers containing one, two or three mannose units are synthesized and formulated into differently patterned supramolecular glycopolymers through homo-assembly or co-assembly with non-functionalized BTAs. Unfortunately, no cellular activity could be detected. Excitingly, these glyco-BTA monomers could be formulated into hydrogels, paving the way for (immune) cell culture.

In the field of soft robotics, knowledge of material science is becoming more and more important. However, many researchers have a background in only one of both domains. To aid the understanding of the other domain, this tutorial describes the complete process from polymer synthesis over fabrication to testing of a soft finger. Enough background is provided during the tutorial such that researchers from both fields can understand and sharpen their knowledge. Self-healing polymers are used in this tutorial, showing that these polymers that were once a specialty, have become accessible for broader use. The use of self-healing polymers allows soft robots to recover from fatal damage, as shown in this tutorial, which increases their lifespan significantly.

The capabilities of scanning Kelvin probe force microscopy (SKPFM) to directly measure local Volta potential differences with relatively high spatial resolution, has made it a very popular technique to assess the relative nobility of intermetallic phases and therefore to understand corrosion susceptibility and microgalvanic corrosion activity in several alloys. However, the direct correlation between galvanic corrosion activity and Volta potential differences measured in air is not straightforward. Several factors, which can easily go unnoticed, can directly affect the potential values measured by SKPFM, hence compromising their validity and relevance in explaining certain galvanic corrosion activities. Several recent studies presenting conflicting/varied results or failing to properly interpret/discuss the obtained data can be found. This work discusses specific factors that can compromise the validity of SKPFM measurements and/or the understanding acquired from them. It presents a discussion on the SKPFM working principle, the basics of galvanic corrosion, and the relevant terminology around these topics, emphasising the possible correlations between them, with the intention of increasing comprehension of SKPFM-based micro-galvanic corrosion studies. A summary of best recommended practices is presented, aiming at standardizing the use of the SKPFM technique and the representation of the data, and to ensure consistency of the results.

Thin films of crystalline and porous metal-organic frameworks (MOFs) have great potential in membranes, sensors, and microelectronic chips. While the morphology and crystallinity of MOF films can be evaluated using widely available techniques, characterizing their pore size, pore volume, and specific surface area is challenging due to the low amount of material and substrate effects. Positron annihilation lifetime spectroscopy (PALS) is introduced as a powerful method to obtain pore size information and depth profiling in MOF films. The complementarity of this approach to established physisorption-based methods such as quartz crystal microbalance (QCM) gravimetry, ellipsometric porosimetry (EP), and Kr physisorption (KrP) is illustrated. This comprehensive discussion on MOF thin film porosimetry is supported by experimental data for thin films of ZIF-8. ispartof: ADVANCED MATERIALS vol:33 issue:17 ispartof: location:Germany status: published

Discrete spacers allow to transversally connect planar textiles and to transform them into pseudo-3D architectures. These 3D textiles can provide the optimal reinforcement in cement composites as the concrete casting process is enhanced and the textile placement within the mould is well-controlled. This research investigated the effect of discrete spacer connections on the flexural properties and cracking behaviour of TRCs and performed a comparison with equivalent 2D TRC systems (same in-plane textiles but without connections) and with knitted 3D textiles. Additional investigated parameters were the material of the reinforcement (glass, carbon) and the density of the textile (fibre volume fraction of the composite). A four-point bending experimental campaign was conducted on four different textile configurations containing (i) no connections (ref), (ii) four spacer connections distributed over the shear zone, (iii) nine spacer connections distributed over the entire length between the supports (both shear and constant moment zone) and (iv) 3D knitted connections. The spacer connections resulted in a pronounced post-cracking stiffness increase and a positive influence on the crack formation of the TRC. Their influence was however dependent on the fibre volume fraction (Vf) of the in-plane reinforcement; configurations with a higher Vf required a higher degree of connections to showing a post-cracking stiffness increase.

The valorization of Fe-rich fayalite slag (FS) as a precursor for alkali-activated materials (AAMs) is hampered by its low reactivity at ambient temperature. Here, FS was blended with waste-based reactive co-binders such as ladle slag (LS) and blast furnace slag (BFS) to improve the fresh and hardened state properties of the AAMs for potential construction applications. The results showed that the incorporation of LS and BFS as an additional source of Ca and Al accelerated the reaction kinetics and influenced the binder gel type and formation mechanism. In all the mixes, Fe, Si and Na are present in the evolving binder gel. In addition to these elements, the binder gel of the blended formulations is also rich in higher quantities of Ca and Al and showed possible formation of C-A-S-H and C-(N)-A-S-H together with the development of andradite, a calcium ferrosilicate hydrate phase formed from chemical interaction between FS and co-binders; it indicates that both FS and co-binder participated in the binder gel formation. Furthermore, the nucleating and filling effects of co-binders improved the workability, ultrasonic pulse velocity and mechanical properties; this also densified the structure and lowered the water absorption and permeable porosity of the blended mortars. The compressive strength of blended mortars was above 20 MPa, thus satisfying the strength requirements of building materials according to ASTM C62. The results of this study emphasize the reuse potential of FS with other waste streams in producing eco-friendly AAMs, which can have a wide range of construction applications.

This work provides a data-oriented overview of the rapidly growing research field covering machine learning (ML) applied to predicting electrochemical corrosion. Our main aim was to determine which ML models have been applied and how well they performed depending on the corrosion topic considered. From an extensive review of corrosion articles presenting comparable performance metrics, a ‘Machine learning for corrosion database’ was created, guiding corrosion experts and model developers in their applications of ML to corrosion. Potential research gaps and recommendations are discussed, and a broad perspective for future research paths is provided.

Reversible poly(methacrylate) networks are synthesized with tunable thermomechanical and self-healing properties. The focus is on high-modulus networks (guide value around 500 MPa at 25 °C) in combination with fast self-healing for applications as coatings at ambient temperature. In case of a broad temperature window for outdoor applications, mechanical robustness up to 120 °C is aimed for. Methacrylate-functionalized Diels-Alder prepolymers containing furan-maleimide reversible covalent bonds are first synthesized at 25 °C. The prepolymers act as reversible crosslinkers in the subsequent UV-polymerization at 60 °C. Reaction-induced phase-separation is achieved by changing the balance between soft and hard blocks, leading to homogeneous and (partially) phase-separated, fully reversible poly(methacrylate) networks. The incorporation of urethane bonds introduces hydrogen bonding capacity. For comparison, irreversible poly(methacrylate) networks, i.e. without reversible Diels-Alder bonds, are synthesized via UV-polymerization of irreversible methacrylate-functionalized prepolymers. A tunable self-healing behavior is demonstrated. The single-dynamic high-modulus poly(methacrylate) networks, i.e. purely based on reversible Diels-Alder bonds, show slowest self-healing, e.g. 7 days in ambient conditions. The dual-dynamic high-modulus poly(methacrylate) networks, i.e. based on covalent Diels-Alder bonding and supramolecular hydrogen bonding, show fastest self-healing, e.g. 10 min in ambient conditions, if hydrogen bonding is combined with intrinsic local network mobility in case of a (partially) phase-separated network morphology.

The development of bio-based polymers displaying promising end-of-life opportunities would have an immense impact on the polymer industry but has remained largely unexplored. Therefore, in this work, self-healing bio-aromatic networks with lignin contents up to 29 wt % were designed based on the thermoreversible Diels−Alder reaction. The networks were developed by reacting a furan-functionalized solvent-extracted lignin and a furan-bearing polyether (F5000) with a bismaleimide (DPBM). The obtained networks were nanophase-separated between a flexible F5000-rich phase and a rigid lignin-rich phase, which was evidenced by (modulated temperature) differential scanning calorimetry and small angle X-ray scattering. Partially due to the phase-separation, improved mechanical properties were obtained, including a higher Young’s modulus and improved toughness. In addition, the thermal stability of the networks significantly increased due to the addition of lignin. Besides the thermomechanical improvement, the networks showed promising stress-relaxation, creep resistance, healing, and reprocessability. A macroscopic healing efficiency of 62% of the toughness was obtained. Moreover, the networks were completely resoluble, which allows for promising recycling possibilities.

It has been suggested that curvature progression in adolescent idiopathic scoliosis occurs through irreversible changes in the intervertebral discs. Strains of mice have been identified who differ in their disc wedging response upon extended asymmetrical compression. Annulus fibrosus tissue remodeling could contribute to the faster disc wedging progression previously observed in these mice. Differences in collagen remodeling capacity of annulus fibrosus cells between these in-bred mice strains was compared using an in vitro micro-tissue system. Annulus fibrosus cells of 8-10 week-old LG/J ("fast-healing") and C57BL/6J ("normal healing") mice were embedded in a micro-tissue platform and cultured for 48 hours. Hereafter, tissues were partially released and cultured for another 96 hours. Micro-tissue surface area and waistcoat contraction, collagen orientation and collagen content were measured. After 96 hours post-release, micro-tissues with annulus fibrosus cells of LG/J mice showed more surface area contraction (p < 0.001) and waistcoat contraction (p = 0.002) than C57BL/6J micro-tissues. Collagen orientation did not differ at 24 hours after partial release. However, at 96 hours, collagen in the micro-tissues from LG/J annulus fibrosus cells was aligned more than in those from C57BL/6J mice (p < 0.001). Collagen content did not differ between micro-tissues at 96 hours. Annulus fibrosus cells of inbred LG/J mice were better able to remodel and realign their collagen fibers than those from C57BL/6J mice. The remodeling of annulus fibrosus tissue could be contributing to the faster disc wedging progression observed in LG/J mice. This article is protected by copyright. All rights reserved.

Electrorefining is the process of choice to purify several metals, among which is copper. A crucial process parameter in electrorefining, and electroplating in general, is the additive activity. Several additives are introduced to the electrolyte to ensure a morphological smooth copper deposit. Thiourea is a crucial but complex additive used in copper electrorefining, it is known to degenerate and both the reaction product as thiourea itself can complex with the copper ions. Unfortunately, time dependent additive studies and mechanistic knowledge of the effect of aged electrolyte on the cathodic part of the electrorefining process are scarce. In this work, operando Odd Random Phase Electrochemical Impedance Spectroscopy (ORP-EIS) is used to study the electrochemistry of a copper plating system containing industrial copper concentrations. The approach applied enables the investigation of the time-varying effect of additives, in this case thiourea and chlorides, assisting the electroplating of copper.

Composites formed by a metal–organic framework (MOF) and an ionic liquid (IL) are potentially interesting materials for applications ranging from gas separation to electrochemical devices. Consequently, there is a need for robust and low-cost preparation procedures that are compatible with the desired applications. We herein report a solvent-free, one-step, and vapor-based ship-in-bottle synthesis of the IL@MOF composite 1-butyl-3-methylimidazolium bromide@ZIF-8 in powder and thin film forms. In this approach, volatile IL precursors evaporate and subsequently adsorb and react within the MOF cages to form the IL.

Two-dimensional (2D) allotropes of tellurium (Te), recently coined as tellurene, are currently an emerging topic of materials research due to the theoretically predicted exotic properties of Te in its ultrathin form and at the single atomic layer limit. However, a prerequisite for the production of such new and single elemental 2D materials is the development of simple and robust fabrication methods. In the present work, we report three different 2D superstructures of Te on Au(111) surfaces by following an alternative experimental deposition approach. We have investigated the superstructures using low-temperature scanning tunneling microscopy and spectroscopy, Auger electron spectroscopy (AES), and field emission AES. Three superstructures (13 × 13, 8 × 4, and √11 × √11) of 2D Te are observed in our experiments, and the formation of these superstructures is accompanied by the lifting of the characteristic 23 × √3 surface reconstruction of the Au(111) surface. Scanning tunneling spectroscopy reveals a strong dependence of the local electronic properties on the structural arrangement of the Te atoms on the Au(111) support, and we observe superstructure-dependent electronic resonances around the Fermi level and below the Au(111) conduction band. In addition to the appearance of the new electronic resonances, the emergence of band gaps with a p-type charge character has been evidenced for two out of three Te superstructures (13 × 13 and √11 × √11) on the Au(111) support.