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Porous scaffolds can be utilized in a variety of biomedical as well as mechanical applications. The process of freeze casting is a successful method to fabricate these porous structures but with ideal characteristics in only one direction (the ice-growth direction). The application of magnetic fields led to an increase in both the microstructural control and mechanical strength in an additional orthogonal direction. The application of these weak, uniform fields (≤20 mT), in particular oscillating fields from a Helmholtz coils setup, has led to increases in mechanical strength through microstructural alignment in multiple material types. However, structures fabricated from these uniform fields have primarily been compared to each other, with little research comparing them to structures fabricated under strong, non-uniform fields from permanent magnet setups. Therefore, iron-oxide scaffolds were fabricated under weak, uniform fields (≤20 mT) as well as strong, non-uniform fields (≥20 mT), and their mechanical and microstructural properties were compared to one another. The application of weak, uniform fields led to superior mechanical properties compared to those produced from the application of strong, non-uniform fields, no distortions in the physical structure of the freeze-cast scaffold, and the best microstructural alignment ever seen in freeze-cast structures. [ABSTRACT FROM AUTHOR]

Hydroxyapatite (HA) is commonly used as a bone substitute material, but it lacks mechanical strength when compared to native bone tissues. To improve the efficacy of HA as a bone substitute by improving the mechanical strength and cell growth attributes, porous composite scaffolds of HA and titania (HA‐TiO2) were fabricated through a freeze‐casting process. Three different compositions by weight percent, 25–75 HA‐TiO2, 50–50 HA‐TiO2, and 75–25 HA‐TiO2, were custom‐made for testing. After sintering at 1250°C, these composite scaffolds exhibited improved mechanical properties compared to porous HA scaffolds. Substrate mixing was observed, which helped reduce crystal size and introduced new phases such as β‐TCP and CaTiO3, which also led to improved mechanical properties. The composition of 50–50 HA‐TiO2 had the highest ultimate compressive strength of 3.12 ± 0.36 MPa and elastic modulus 63.29 ± 28.75 MPa. Human osteoblast cell proliferation assay also increased on all three different compositions when compared to porous HA at 14 days. These results highlight the potential of freeze casting composites for the fabrication of bone substitutes, which provide enhanced mechanical strength and biocompatibility while maintaining porosity. [ABSTRACT FROM AUTHOR]

Fungi are an incredibly diverse biological kingdom with organisms that have a wide range of morphologies, properties, and structures. Previous research has investigated the use of filamentous fungi, which have naturally porous structures created by hyphal filaments, as a means of phytoremediation. This study uses these natural fungal structures to create bioinspired materials that capture both the structure and functional absorption properties of fungi. Three types of filamentous fungi with different hyphal structures (monomitic, dimitic, and trimitic) are used as organic templates to create inorganic media using two different biotemplating methods to create silica and hybrid samples. Characterization of these samples is completed using scanning electron microscope imaging, chemical characterization, nanoindentation, and hydrophilic and oleophilic absorption tests. Biotemplated samples have similar structures as their organic templates, but contained silica, which is not present in natural, dehydrated fungal samples. Fourier transform infrared analysis shows better cross‐linking in the hybrid samples, which also have higher mechanical resistance than the silica samples. Absorption testing demonstrates that silica samples are closest to mimicking the absorption properties of natural, dehydrated samples. Of the three hyphal structures, the monomitic samples show the greatest increase in mechanical properties and maintenance of absorption properties when biotemplated. [ABSTRACT FROM AUTHOR]

Magnetic freeze casting utilizes the freezing of water, a low magnetic field and surface magnetized materials to make multi-axis strengthened porous scaffolds. A much greater magnetic moment was measured for larger magnetized alumina platelets compared with smaller particles, which indicated that more platelet aggregation occurred within slurries. This led to more lamellar wall alignment along the magnetic field direction during magnetic freeze casting at 75 mT. Slurries with varying ratios of magnetized particles to platelets (0:1, 1:3, 1:1, 3:1, 7:1, 1:0) produced porous scaffolds with different structural features and degrees of lamellar wall alignment. The greatest mechanical enhancement in the magnetic field direction was identified in the synergistic condition with the highest particle to platelet ratio (7:1). Magnetic freeze casting with varying ratios of magnetized anisotropic and isotropic alumina provided insights about how heterogeneous morphologies aggregate within lamellar walls that impact mechanical properties. Fabrication of strengthened scaffolds with multi-axis aligned porosity was achieved without introducing different solid materials, freezing agents or additives. Resemblance of 7:1 particle to platelet scaffold microstructure to wood light-frame house construction is framed in the context of assembly inspiration being derived from both natural and synthetic sources. [ABSTRACT FROM AUTHOR]

The boxfish ( Lactoria cornuta ) has a carapace consisting of dermal scutes with a highly mineralized surface plate and a compliant collagen base. This carapace must provide effective protection against predators as it comes at the high cost of reduced mobility and speed. The mineralized hydroxyapatite plates, predominantly hexagonal in shape, are reinforced with raised struts that extend from the center toward the edges of each scute. Below the mineralized plates are non-mineralized collagen fibers arranged in through-the-thickness layers of ladder-like formations. At the interfaces between scutes, the mineralized plates form suture-like teeth structures below which the collagen fibers bridge the gap between neighboring scutes. These sutures are unlike most others as they have no bridging Sharpey’s fibers and appear to add little mechanical strength to the overall carapace. It is proposed that the sutured interface either allows for accommodation of the changing pressures of the boxfish’s ocean habitat or growth, which occurs without molting or shedding. In both tension and punch testing the mineralized sutures remain relatively intact while most failures occur within the collagen fibers, allowing for the individual scutes to maintain their integrity. This complex structure allows for elevated strength of the carapace through an increase in the stressed area when attacked by predators in both penetrating and crushing modes. [ABSTRACT FROM AUTHOR]

Comprehensive studies comparing tensile properties of sutures are over 25 years old and do not include recent advances in suture materials. Accordingly, the objective of this article is to investigate the tensile properties of commonly used sutures in cutaneous surgery. Thirteen 3-0 sized modern sutures (four nonabsorbable and nine absorbable) were tensile tested in both straight and knotted configurations according to the procedures outlined by the United States Pharmacopeia. Glycomer 631 was found to have the highest failure load (56.1 N) of unknotted absorbable sutures, while polyglyconate (34.2 N) and glycomer 631 (34.3 N) had the highest failure loads of knotted absorbable sutures. Nylon (30.9 N) and polypropylene (18.9 N) had the greatest failure loads of straight and knotted nonabsorbable sutures, respectively. Polydioxane was found to have the most elongation prior to breakage (144%) of absorbable sutures. Silk (8701 MPa) and rapid polyglactin 910 (9320 MPa) had the highest initial modulus of nonabsorbable and absorbable sutures, respectively. The new data presented in the study provide important information for guiding the selection of suture materials for specific surgeries. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 103B: 735-742, 2015. [ABSTRACT FROM AUTHOR]

Research is conducted into freeze‐casting of surface‐magnetized Fe3O4 particles under uniform, low‐strength magnetic fields (5.2 mT) to mimic the mechanical characteristics of natural human bone. Freeze‐casting is a technique that fabricates porous materials by directionally freezing and sublimating an aqueous slurry. A novel, Helmholtz coil‐based freeze‐caster is developed and it is shown that, during freeze‐casting, the use of this Helmholtz coil generates a more uniform magnetic field than permanent magnets. This uniform magnetic field, applied in the direction of ice growth, keeps particles from agglomerating and results in an increase of 55% in both the ultimate compressive strength and the elastic modulus of porous surface‐magnetized Fe3O4 scaffolds. These increases can be linked to a reduction in the porosity that occurs due to magnetic interactions between particles in the presence of the field. These results offer a novel method for the fabrication of bone‐inspired biomaterials and structural materials. The results show that the mechanical properties (ultimate compression strength and elastic modulus) of freeze‐cast scaffolds are increased when using a magnetic field. This is done using surface‐magnetized Fe3O4 particles and applying a uniform magnetic field in the ice‐growth direction generated by a Helmholtz Coil resulting in a decrease in the pore size and porosity. [ABSTRACT FROM AUTHOR]

With the continuous growth in global population, energy demands are summoning the development of novel materials with high specific surface areas (SSA) for energy and environmental applications. High-SSA silica-based materials, such as aerogels, are highly popular as they are easy to form and tune. They also provide thermal stability and easy functionalization, which leads to their application in batteries, heavy metal adsorption, and gas capture. However, owing to large pore volumes, high-SSA silica exhibits weak mechanical behavior, requiring enhancement or modification to improve the mechanical properties and make them viable for these applications. The creation of macropores in these mesoporous solids is also desirable for applications utilizing membranes. To facilitate research in these critical areas, this review describes the research into sol-gel formation of silica, as well as polymer-based tailoring carried out in the last decade. Additionally, this review summarizes applications of polymer-tailored high-SSA silica materials in the energy and environmental fields and discusses the challenges associated with implementing and scaling of these materials for these applications. [Display omitted] • Polymers are used to tailor the properties of sol-gel derived high specific surface area silicates. • Polymers can be incorporated into silica to improve the mechanical durability. • Polymers can be used as porogens to tailor the microstructure (meso- and macropores). • High specific surface area silicates are used for energy storage and environmental remediation. [ABSTRACT FROM AUTHOR]