Three-dimensional bioprinting uses additive manufacturing techniques for the automated fabrication of hierarchically organized living constructs. The building blocks are often hydrogel-based bioinks, ...which need to be printed into structures with high shape fidelity to the intended computer-aided design. For optimal cell performance, relatively soft and printable inks are preferred, although these undergo significant deformation during the printing process, which may impair shape fidelity. While the concept of good or poor printability seems rather intuitive, its quantitative definition lacks consensus and depends on multiple rheological and chemical parameters of the ink. This review discusses qualitative and quantitative methodologies to evaluate printability of bioinks for extrusion- and lithography-based bioprinting. The physicochemical parameters influencing shape fidelity are discussed, together with their importance in establishing new models, predictive tools and printing methods that are deemed instrumental for the design of next-generation bioinks, and for reproducible comparison of their structural performance.
The production of cream cheese from ultrafiltered (UF) milk can reduce acid whey generation but the effect of altered protein and calcium concentration on the physicochemical properties of cream ...cheese is not well understood. In this study, the effect of skim milk concentration by UF (2.5 and 5 fold) was assessed both with and without calcium reduction using 2% (w/v) cation resin treatment. UF concentration increased the concentration of peptides and free amino acids and led to a more heterogeneous and porous microstructure, resulting in a softer, less viscous and less thermally stable cream cheese. Calcium reduction decreased peptide generation, increased the size of corpuscular structures, decreased porosity and increased thermal stability but did not significantly decrease cheese hardness or viscosity. The study illustrates how protein or calcium concentration, can be used to alter functional properties.
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•Cream cheese properties were tailored by ultrafiltration and calcium reduction.•Peptides, porosity, heterogeneity and softness were increased in UF cream cheese.•Reducing calcium decreased production of peptides and altered structure.•Thermal stability was increased by calcium reduction but not hardness or viscosity.
•Textile fibre derived from end-of-life tyres (TFELT) is an environmental problem.•The physical and rheological properties of asphalt binders can be improved by the addition of fibres.•This work ...evaluates the effects of the innovative addition of TFELT, in three percentages, on the mechanical and rheological properties of two asphalt binders.•The results are consistent and indicate significant improvements in high temperature performance, while maintaining performance at intermediate and low temperatures.
End-of-Life Tyres (ELT) consist of rubber, steel and textile fibre (TFELT). Unlike rubber and steel, the possibilities for the re-use of TFELT are limited, and its final disposal is an environmental problem. This article explores an alternative re-use of TFELT as an additive for asphalt binder (AB). The TFELT was characterised using scanning electron microscope (SEM), polarized microscopy and thermogravimetric analysis. Two Asphalt Binders (AB14 and AB24) and three addition percentages (0.1%, 0.3% and 0.5%) were evaluated. The effects on the physical properties at high, intermediate and low temperature were studied by determining the softening point, penetration and FRAASS breaking point. We also evaluated the effects on the rheological properties, by determining the rutting and fatigue parameters at different states of ageing (short and long term). Resistance to the accumulation of deformations was measured by applying the Multiple Stress Creep Recovery test (MSCR), and resistance to fatigue by the Linear Amplitude Sweep test (LAS). The results showed significant effects in reducing the accumulation of permanent deformation, by up to 40% for the addition of 0.5% TFELT, without any reduction in properties of resistance to thermal cracking.
The ternary edible films based on commercial or bio-chemical chitosan (CCh or BCh) and starch (S) with different concentration of gallic acid (GA) were produced by casting. This work analyzed the ...effect of different type of Ch and GA concentrations (1.25 mg/gTB and 2.5 mg/gTB) on the rheological properties of the film-forming solutions, as well as physicochemical (thickness, moisture content, swelling index, water vapor permeability (WVP), tensile strength, microstructure, opacity, and color) and antioxidant properties of the edible films themselves. The chemical cross-linking between the GA and Ch into the edible films of biopolymers could form of ester linkages between the carboxyl groups of GA and the hydroxyl groups of Ch. Results showed that the ternary edible films of BCh-S-GA5.0 resulted with a positive effect on their rheological (η0, λ, and p), physicochemical (WVP, swelling, tensile strength, microstructure) and antioxidant properties. The greatest incorporation of polyphenol into the BCh-S-GA5.0 films greatly reduced WVP and swelling values in approximately 61.01% and 23%, respectively also the tensile strength value increased to 37.372 MPa. The ternary edible films developed in this study showed many desirable characteristics, which could potentially be used as bioactive packaging films for food applications.
•The influence of several modifiers on bitumen is testified.•The relationship between components and performance of bitumen is revealed.•A model of bitumen microstructure changing with components is ...proposed.
In order to investigate the impact of bitumen components on its overall properties, various modified bitumen with 1.0 %PPA or 2.0 %SBS/SBR + 0.6 %PPA were prepared. The influence of PPA dosage on bitumen’s physical properties were evaluated, and the macroscopic and microscopic properties of each bitumen sample were characterized by DSR, BBR and atomic force microscopy observation. The components of bitumen were separated through SARA test, and the infrared spectroscopy of asphaltenes was further analyzed. The findings suggest a significant impact on bitumen with PPA incorporation, the elastic recovery properties of bitumen at high temperatures were enhanced due to a more stable colloidal structure was formed by the dispersion and interaction of macromolecular asphaltenes. However, the low-temperature rheological properties of bitumen were impaired by reason of a relatively reduced flowable lightweight component. Specifically, the large asphaltenes clusters were dispersed cause PPA reacted with the –OH bonds of alcohols in bitumen by phosphorylation. By modeling the correlation between bitumen component contents and its microscopic surface parameters, the asphaltenes decomposition was demonstrated to be an important factor on the microscopic morphology, which was also related to the content of saturates and aromatics. Thus, a method for deconstructing bitumen from a compositional perspective is proposed.
Over the past decade, 3D concrete printing has shown enormous application potential for the industry. The new technology poses specific requirements on 3D printable concrete (3DPC), especially on its ...rheological properties in the fresh state. The current codes and standards for conventional concrete construction are not applicable for guiding the mix design of 3DPC. Developing robust mix-design guidelines of printable concrete while considering the principles of sustainability, use of indigenous materials and available printer characteristics contributes to a broader practical application of 3DPC. This article presents state-of-the-art on mix design concepts for 3DPC. In this, various aspects of mixture compositions and their effects on properties of 3DPC are highlighted and mix design approaches are described. While currently and out of necessity, a trial and error approach remains the norm, for finding the appropriate mix composition for 3DPC, it would clearly be beneficial to develop rational and scientific guidelines for a particular set of parameters. Thus, the use of models providing a quantitative relationship between the rheological parameters of fresh concrete and its composition is instrumental to guide the mix design of printable concrete. Some such models do exist already, but considerable research is still needed to develop them into reliable mix design tools. Furthermore, the contemporary mix design for 3DPC mainly focuses on the printability of concrete in fresh state, while the characteristics of hardened concrete such as strength or durability are often not targeted explicitly. Given the engineering application of 3DPC, further research is needed to develop mix design concepts involving the targeted properties of hardened concrete under consideration of process-induced anisotropy.
Thermal interface materials (TIMs) are vital to dissipate excess heat generated by electronic components with ever-growing power density to ensure their reliability and performance. However, the ...limited dispersibility of nano-sized thermal conductive fillers hinders further enhancement of thermal conductivity in TIMs. It remains challenging to manufacture high-performance TIMs with simultaneous high thermal conductivity, low cost, and capability of large-scale production. Herein, a solvent-free and scalable approach was adopted to fabricate asphalt/graphite nanoplatelets (GNPs) composites by in situ exfoliating graphite in asphalt melt using a three-roll mill. During exfoliation, asphalt was adsorbed onto the surface of GNPs via π-π interaction and improved their dispersibility. Hence, GNPs formed integrated thermal conductive pathways with reduced interfacial thermal resistance, which significantly improved the thermal conductivity of asphalt/GNP composites. At 25 vol% loading, the asphalt/GNP composite displayed a thermal conductivity of 1.95 W m−1 K−1, showing a 114 % increase compared to the asphalt/commercial GNP (c-GNP) composite prepared by conventional mechanical mixing. Moreover, the heat-resistant and mechanical properties of the asphalt/GNP composites were also enhanced due to the improved filler dispersion and filler-matrix interactions. Thus, the asphalt/GNP composites fabricated by in situ three-roll milling possessed remarkable advantages as TIMs compared with asphalt/c-GNP composites and commercial silicone rubber thermal pads.
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A new family of materials comprised of cellulose, cellulose nanomaterials (CNMs), having properties and functionalities distinct from molecular cellulose and wood pulp, is being developed for ...applications that were once thought impossible for cellulosic materials. Commercialization, paralleled by research in this field, is fueled by the unique combination of characteristics, such as high on-axis stiffness, sustainability, scalability, and mechanical reinforcement of a wide variety of materials, leading to their utility across a broad spectrum of high-performance material applications. However, with this exponential growth in interest/activity, the development of measurement protocols necessary for consistent, reliable and accurate materials characterization has been outpaced. These protocols, developed in the broader research community, are critical for the advancement in understanding, process optimization, and utilization of CNMs in materials development. This review establishes detailed best practices, methods and techniques for characterizing CNM particle morphology, surface chemistry, surface charge, purity, crystallinity, rheological properties, mechanical properties, and toxicity for two distinct forms of CNMs: cellulose nanocrystals and cellulose nanofibrils.
Reliable characterization of cellulose nanomaterials is critical for their utilization in various applications.
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