Light-Induced Self-Assembled Polydiacetylene/Carbon Dot Functional "Honeycomb"

The design of functional supramolecular assemblies from individual molecular building blocks is a fundamental challenge in chemistry and material science. We report on the fabrication of "honeycomb" films by light-induced coassembly of diacetylene derivatives and carbon dots. Specifically, modulating noncovalent interactions between the carbon dots, macrocyclic diacetylene, and anthraquinone diacetylene facilitates formation of thin films exhibiting a long-range, uniform pore structure. We show that light irradiation at distinct wavelengths plays a key role in the assembly process and generation of unique macro-porous morphology, by both initiating interactions between the carbon dots and the anthraquinone moieties and giving rise to the topotactic polymerization of the polydiacetylene network. We further demonstrate utilization of the macro-porous film as a photocatalytic platform for water pollutant degradation and as potential supercapacitor electrodes, both applications taking advantage of the high surface area, hydrophobicity, and pore structure of the film.

Energy Absorption of 3D Printed ABS and TPU Multimaterial Honeycomb Structures

Advances in multimaterial 3D printing are enabling the construction of advantageous engineering structures that benefit from material synergies. Cellular structures, such as honeycombs, provide high-energy absorption to weight ratios that could benefit from multimaterial strategies to improve the safety and performance of engineered systems. In this study, we investigate the energy absorption for honeycombs with square and hexagonal unit cells constructed from acrylonitrile butadiene styrene (ABS) and thermoplastic polyurethane (TPU). Honeycombs were fabricated and tested for out-of-plane and in-plane compression using ABS, TPU, and a combination of ABS with a central TPU band of tunable height. Out-of-plane energy absorption for square honeycombs increased from 2.2 kN·mm for TPU samples to 11.5 kN·mm for ABS samples and energy absorption of hexagonal honeycombs increased from 2.9 to 15.1 kN·mm as proportions of TPU/ABS were altered. In-plane loading demonstrated a sequential collapse of unit cell rows in square honeycombs with energy absorption of 0.1 to 2.6 kN·mm and a gradual failure of hexagonal honeycombs with energy absorption of 0.6 to 2.0 kN·mm. These results demonstrate how multimaterial combinations affect honeycomb compressive response by highlighting their benefits for controlled energy absorption and deformation for tunable performance in diverse engineering applications.

Evaluation of an Elastomeric Honeycomb Bicycle Helmet Design to Mitigate Head Kinematics in Oblique Impacts

Head impacts in bicycle accidents are typically oblique to the impact surface and transmit both normal and tangential forces to the head, causing linear and rotational head kinematics, respectively. Traditional expanded polystyrene (EPS) foam bicycle helmets are effective at preventing many head injuries, especially skull fractures and severe traumatic brain injuries (TBIs) (primarily from normal contact forces). However, the incidence of concussion from collisions (primarily from rotational head motion) remains high, indicating need for enhanced protection. An elastomeric honeycomb helmet design is proposed herein as an alternative to EPS foam to improve TBI protection and be potentially reusable for multiple impacts, and tested using a twin-wire drop tower. Small-scale normal and oblique impact tests showed honeycomb had lower oblique strength than EPS foam, beneficial for diffuse TBI protection by permitting greater shear deformation and had the potential to be reusable. Honeycomb helmets were developed based on the geometry of an existing EPS foam helmet, prototypes were three-dimensional-printed with thermoplastic polyurethane and full-scale flat and oblique drop tests were performed. In flat impacts, honeycomb helmets resulted in a 34% higher peak linear acceleration and 7% lower head injury criteria (HIC15) than EPS foam helmets. In oblique tests, honeycomb helmets resulted in a 30% lower HIC15 and 40% lower peak rotational acceleration compared to EPS foam helmets. This new helmet design has the potential to reduce the risk of TBI in a bicycle accident, and as such, reduce its social and economic burden. Also, the honeycomb design showed potential to be effective for repetitive impact events without the need for replacement, offering benefits to consumers.

Effect of 3D-Printed Honeycomb Core on Compressive Property of Hybrid Energy Absorbers: Experimental Testing and Optimization Analysis

This paper presents an innovative method of constructing energy absorbers, whose primary function is to effectively transform kinetic energy into strain energy in events with high deformation rates. Hybrid specimens are proposed considering thin-walled windowed metallic tubes filled with 3D-printed hexagonal honeycombs made of PET-G and ABS thermoplastic. The patterned windows dimensions vary from 20 × 20, 20 × 30, 15 × 20 and 15 × 30 mm2. Although using polymers in engineering and thin-walled sections is not new, their combination has not been explored in this type of structure designed to withstand impacts. Specimens resist out-of-plane quasi-static axial loading, and test results are analyzed, demonstrating that polymer core gives the samples better performance parameters than unfilled samples regarding energy absorption (Ea), load rate (LR), and structural effectiveness (η). An optimization procedure using specialized software was applied to evaluate experimental results, which led to identifying the optimal window geometry (16.4 × 20 mm2, in case) and polymer to be used (ABS). The optimized sample was constructed and tested for axial compression to validate the optimization outcomes. The results reveal that the optimal sample performed similarly to the estimated parameters, making this geometry the best choice under the test conditions.

Applicative Assessment of a Selective Laser Melting 3D-Printed Ti-6Al-4 V Plate with a Honeycomb Structure in the Reconstruction of a Mandibular Defect of a Beagle Dog

The most challenging problem in oral and maxillofacial surgery is the reconstruction of defects for the oral and maxillofacial complex. Transfer of different autografts is known as the "gold standard" for the reconstruction of bone defects in the oral and maxillofacial region. Graft harvesting, however, can lead to many complications, such as donor-site morbidity, surgical time-consuming, etc. Three-dimensional (3D) printing technology is an innovative technique that allows the fabrication of personalized plates and scaffolds to fit the precise anatomy of an individual's defect. In this study, a selective laser melting 3D-printed Ti-6Al-4 V plate with a honeycomb was designed, and its physical and biological features were characterized. The personalized 3D-printed scaffold and commercialized titanium reconstruction plate were applied to reconstruct a 4 cm mandibular defect in a beagle dog. Effects of the treatment were analyzed radiologically and histologically. Our results showed that the application of a 3D-printed plate with a honeycomb achieved good biocompatibility and osseointegration and has potential clinical application.

Visco-Elastic Honeycomb Structures with Increased Energy Absorption and Shape Recovery Performance Using Buckling Initiators

Energy-absorbing materials have extensive applications in aerospace and automotive applications. Research has shown buckling initiators, or triggers, in energy-absorbing tubular structures increase the energy absorbed by encouraging the side panels to fold when loaded out of plane in compression conditions. Additively manufactured TPE honeycombs were designed in this study to include these buckling initiators, which introduced a slight decrease in initial weight, as well as initial stress concentrations, while improving crashworthiness characteristics. The samples with buckling initiators (1BI) showed an increase in crush efficiency when directly compared to their no buckling initiator (0BI) counterparts. The 1BI samples maintained an increased crush efficiency regardless of the strain rate used. The samples with 1BI were able to better equilibrate the peak stress with the plateau stress. These honeycomb samples were found to maintain their crush efficiency, even after multiple rounds of compression testing. The quasi-static 0BI samples experienced a 23.4% decrease in the peak stress after multiple rounds of compression testing, while the 1BI samples saw approximately a 23.0% decrease. The 1BI samples averaged a decrease in crush efficiency of 0.5%, while the 0BI samples saw a decrease in crush efficiency of 5%. As the strain rate increased, the crush efficiency for the 1BI samples showed an increase in performance, with a smaller degradation in crush efficiency over multiple uses. Visco-elastic honeycomb with buckling initiators has a higher energy absorption than samples with no buckling initiators when exposed to multiple impact cycles.

Electron spin resonance study on the 4fhoneycomb quantum magnet YbCl3

The local magnetic properties of Yb³⁺in the layered honeycomb material YbCl₃were investigated by electron spin resonance on single crystals. For in-plane and out-of-plane field orientations theg-factor shows a clear anisotropy (g∥=2.97(8)andg⊥=1.53(4)), whereas the low temperature exchange coupling and the spin relaxation display a rather isotropic character. At elevated temperatures the contribution of the first excited crystal field level (21±2meV) dominates the spin relaxation.

Recent Progress on Honeycomb Layered Oxides as a Durable Cathode Material for Sodium-Ion Batteries

Sodium-ion batteries (SIBs) are becoming promising candidates for energy storage devices due to the low cost, abundant reserves, and excellent electrochemical performance. As the most important unit, layered cathodes attract much attention, where honeycomb-layered-oxides (HLOs) manifest outstanding structural stability, high redox potential, and long-life electrochemistry. Here, recent progress on HLOs as well as Na₃ Ni₂ SbO₆ and Na₃ Ni₂ BiO₆ as two representative materials are introduced, and the crystal and electronic structure, electrochemical performance, and modification strategies are summarized. The advanced high nickel HLOs are highlighted toward development of state-of-the-art sodium-ion batteries. This review would deepen the understanding of superstructure in layered oxides, as well as structure-property relationship, and inspire more interest in high output voltage, long lifespan sodium-ion batteries.

A Study of Aluminum Honeycomb Structures under Dynamic Loading, with Consideration Given to the Effects of Air Leakage

Aluminum honeycomb structures are used in the construction of protective materials due to the positive relationship between their mass and their energy-absorbing properties. Applying such materials in the construction of large machinery, such as military vehicles, requires the development of a new method of finite element modeling, one that considers conditions with high strain rates, because a material model is currently lacking in the available simulation software, including LS-DYNA. In the present study, we proposed and verified a method of numerically modeling honeycomb materials using a simplified Y element. Results with a good level of agreement between the full core model and the Y element were achieved. The obtained description of the material properties was used in the subsequent creation of a homogeneous model. In addition, we considered the influence of increases in pressure and the leakage of the air entrapped in the honeycomb cells. As a result, we were able to attain a high level of accuracy regarding the stress values across the entire range of progressive failure, from the loss of stability to full core densification, and across a wide range of strain rates.

Optimization of Hexagonal Structure for Enhancing Heat Transfer in Storage System

Thermal performance was tested during cycling work for latent heat storage systems based on KNO₃ and NaNO₃ (weight ratio 54:46). For heat transfer improvement, cast aluminum honeycomb-shaped structures were produced via 3D printing of polymer model and investment casting. Different wall thicknesses were tested at 1.2 mm and 1.6 mm. The obtained results were compared to working cycles of pure PCM bed. The use of enhancers is reported to improve the rate of charging and discharging of the deposit. In the next step, the structures were examined with numerical simulation performed with ANSYS Fluent software. The wall thicknesses taken into consideration were the following: 0.8, 1.2, 1.6, and 2.0 mm. An insert with a greater wall thickness allows for smaller dT/dt and better heat distribution in the vessel. The investment casting process enables the manufacturing of complex structures of custom shapes without porosity and contamination.

Biopolymer Honeycomb Microstructures: A Review

In this review, we present a comprehensive summary of the formation of honeycomb microstructures and their applications, which include tissue engineering, antibacterial materials, replication processes or sensors. The history of the honeycomb pattern, the first experiments, which mostly involved the breath figure procedure and the improved phase separation, the most recent approach to honeycomb pattern formation, are described in detail. Subsequent surface modifications of the pattern, which involve physical and chemical modifications and further enhancement of the surface properties, are also introduced. Different aspects influencing the polymer formation, such as the substrate influence, a particular polymer or solvent, which may significantly contribute to pattern formation, and thus influence the target structural properties, are also discussed.

On the Behavior of Honeycomb, Grid and Triangular PLA Structures under Symmetric and Asymmetric Bending

Additive manufacturing technologies enable the production of components with lightweight cores, by means of infills with various patterns and densities. Together with reduced mass and material consumption, infill geometries must ensure that strength and stiffness conditions are fulfilled. For the proper correlation of the infill type with the loading case of the part, the mechanical behavior of the infill along all three principal axes of inertia has to be known. In this paper, the behavior in symmetric and asymmetric bending of three infill geometries, commonly used in 3D printing processes (honeycomb, grid and triangles) is analyzed. The variations of deflections as a function of force orientation are presented, showing that honeycomb and triangular structures exhibit similar behaviors along the Y and Z principal axes of inertia. Furthermore, the displacements obtained for the three types of structures are compared, in relation to the consumed volume of material. The larger displacements of the grid structure compared to the honeycomb and triangular structures are highlighted.

Crystallography of honeycomb formation under geometric frustration

As honeybees build their nests in preexisting tree cavities, they must deal with the presence of geometric constraints, resulting in nonregular hexagons and topological defects in the comb. In this work, we study how bees adapt to their environment in order to regulate the comb structure. Specifically, we identify the irregularities in honeycomb structure in the presence of various geometric frustrations. We 3D-print experimental frames with a variety of constraints imposed on the imprinted foundations. The combs constructed by the bees show clear evidence of recurring patterns in response to specific geometric frustrations on these starter frames. Furthermore, using an experimental-modeling framework, we demonstrate that these patterns can be successfully modeled and replicated through a simulated annealing process, in which the minimized potential is a variation of the Lennard-Jones potential that considers only first-neighbor interactions according to a Delaunay triangulation. Our simulation results not only confirm the connection between honeycomb structures and other crystal systems such as graphene, but also show that irregularities in the honeycomb structure can be explained as the result of analogous interactions between cells and their immediate surroundings, leading to emergent global order. Additionally, our computational model can be used as a first step to describe specific strategies that bees use to effectively solve geometric mismatches while minimizing cost of comb building.

The Functionalization of a Honeycomb Polystyrene Pattern by Excimer Treatment in Liquid

In this article, we present a unique combination of techniques focusing on the immobilization of noble metal nanoparticles into a honeycomb polystyrene pattern prepared with the improved phase-separation technique. The procedure consists of two main steps: the preparation of the honeycomb pattern (HCP) on a perfluoroethylenepropylene substrate (FEP), followed by an immobilization procedure realized by the honeycomb pattern's exposure to an excimer laser in a noble metal nanoparticle solution. The surface physico-chemical properties, mainly the surface morphology and chemistry, are characterized in detail in the study. The two-step procedure represents the unique architecture of the surface immobilization process, which reveals a wide range of potential applications, mainly in tissue engineering, but also as substrates for analytical use.

Experimental and Numerical Analysis of Chlorinated Polyethylene Honeycomb Mechanical Performance as Opposed to an Aluminum Alloy Design

Manufacturing aircraft components through 3D printing has become a widespread concept with proven applicability for serial production of certain structural parts. The main objective of the research study is to determine whether a chlorinated polyethylene material reinforced with milled carbon fibers has the potential of replacing the current 5052 NIDA aluminum alloy core of the IAR330 helicopter tail rotor blade, under the form of a honeycomb structure with hexagonal cells. Achieving this purpose implied determining the tensile and compression mechanical properties of the material realized by fused deposition modeling. The tensile tests have been conducted on specimens manufactured on three printing directions, so that the orthotropic nature of the material may be taken into account. The bare compression tests were realized on specimens manufactured from both materials, with similar honeycomb characteristics. All the mechanical tests have been performed on the Instron 8872 servo hydraulic testing system and the results have been evaluated with the Dantec Q400 Digital Image Correlation system. The experimental tests have been reproduced as finite element analyses which have been validated by results comparison, in order to determine if the compression model is viable for more complex numerical analysis.

Channel Aperture Characteristics of Carbonate Apatite Honeycomb Scaffolds Affect Ingrowths of Bone and Fibrous Tissues in Vertical Bone Augmentation

Synthetic scaffolds with the ability to prevent fibrous tissue penetration and promote bone augmentation may realize guided bone regeneration without the use of a barrier membrane for dental implantation. Here, we fabricated two types of honeycomb scaffolds of carbonate apatite, a bone mineral analog, whose channel apertures were square (HC-S) and rectangular (HC-R). The side lengths of the HC-Ss and HC-Rs were 265.8 ± 8.9; 817.7 ± 2.4 and 267.1 ± 5.2 μm, respectively. We placed cylindrical HC-Ss and HC-Rs on the rabbit calvaria. At 4 weeks post-implantation, the HC-Ss prevented fibrous tissue penetration from the top face via the channels, which allowed the new bone to reach the top of the scaffold from the bottom face or the calvarium. In contrast, in the HC-Rs, fibrous tissues filled the channels in the top region. At 12 weeks post-implantation, the HC-Ss were partially replaced with new bone. In the top region of the HC-Rs, although new bone had formed, fibrous tissue remained. According to the findings here and in our previous study, the longer side length rather than the shorter side length of a rectangular scaffold channel aperture is the dominant factor that affects fibrous tissue penetration and new bone augmentation. Furthermore, even though channel aperture areas are similar, bone and fibrous tissue ingrowths are different when the aperture shapes are different.

Honeycomb, a New Food Resource with Health Care Functions: The Difference of Volatile Compounds found in Apis cerana and A. mellifera Honeycombs

The honeycomb composition is very complex, containing honey, royal jelly, pollen, and propolis, and thus contains a large number of bioactive ingredients, such as polyphenols and flavonoids. In recent years, honeycomb as a new functional food resource has been favored by many bee product companies, but the basic research on honeycomb is lacking. The aim of this study is to reveal the chemical differences between A. cerana honeycombs (ACC) and A. mellifera honeycombs (AMC). In this paper, we studied the volatile organic components (VOCs) of ACC and AMC by solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME/GC-MS). A total of 114 VOCs were identified in 10 honeycombs. Furthermore, principal component analysis (PCA) revealed that the chemical composition of ACC and AMC were different. Additionally, orthogonal partial least squares discrimination analysis (OPLS-DA) revealed that benzaldehyde, octanal, limonene, ocimene, linalool, α-terpineol, and decanal are the significant VOCs in AMC extracts, which are mainly derived from propolis. OPLS-DA model also identified 2-phenylethanol, phenethyl acetate, isophorone, 4-oxoisophorone, betula, ethyl phenylacetate, ethyl palmitate, and dihydrooxophorone as potential discriminatory markers of ACC, which likely contribute to protecting the hive against microorganisms and keep it clean.

Effects of Scaffold Shape on Bone Regeneration: Tiny Shape Differences Affect the Entire System

Although studies on scaffolds for tissue generation have mainly focused on the chemical composition and pore structure, the effects of scaffold shape have been overlooked. Scaffold shape determines the scaffold surface area (SA) at the single-scaffold level (i.e., microscopic effects), although it also affects the amount of interscaffold space in the tissue defect at the whole-system level (i.e., macroscopic effects). To clarify these microscopic and macroscopic effects, this study reports the osteogenesis abilities of three types of carbonate apatite granular scaffolds with different shapes, namely, irregularly shaped dense granules (DGs) and two types of honeycomb granules (HCGs) with seven hexagonal channels (∼255 μm in length between opposite sides). The HCGs possessed either 12 protuberances (∼75 μm in length) or no protuberances. Protuberances increased the SA of each granule by 3.24 mm² while also widening interscaffold spaces and increasing the space percentage in the defect by ∼7.6%. Interscaffold spaces were lower in DGs than HCGs. On DGs, new bone formed only on the surface, whereas on HCGs, bone simultaneously formed on the surface and in intrascaffold channels. Interestingly, HCGs without protuberances formed approximately 30% more new bone than those with protuberances. Thus, even tiny protuberances on the scaffold surface can affect the percentage of interscaffold space, thereby exerting dominant effects on osteogenesis. Our findings demonstrate that bone regeneration can be improved by considering macroscopic shape effects beyond the microscopic effects of the scaffold.

Cell Viability Assay and Surface Morphology Analysis of Carbonated Hydroxyapatite/Honeycomb/Titanium Alloy Coatings for Bone Implant Applications

In this work, carbonated hydroxyapatite/titanium alloy (CHA/Ti) and carbonated hydroxyapatite/honeycomb/titanium alloy (CHA/HCB/Ti) plates were coated using the electrophoretic deposition dip coating (EP2D) method. Analysis of cell viability and surface morphology of CHA/Ti and CHA/HCB/Ti coatings were carried out using the MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay and scanning electron microscopy (SEM), respectively. In a previous study, the thickness and average compressive strength values for the CHA/Ti and CHA/HCB/Ti plates were about 63−89 μm and 54−75 MPa, respectively. The result for thickness and compressive strength in this research followed the thickness and compressive strength parameters for coating in bone implants. In this work, the cell viability for incubation times during 24 h and 48 h of CHA/Ti plates is demonstrably superior to that of CHA/HCB/Ti plates, respectively, where the cell viability for CHA/Ti plates increased to ((67 ± 2)%) after incubation for 48 h. According to the one-way analysis of variance (ANOVA), the p-value was <0.05, indicating a significant difference in the average cell viability value across the three groups. Furthermore, the surface of CHA/Ti is not changed after the coating process. These results will yield many positive biomedical applications, especially in bone implants. Overall, CHA/Ti and CHA/HCB/Ti plates can be considered candidates for biomedical applications based on an analysis of surface morphology and cell viability.

The Comparative approach to bio-inspired design: integrating biodiversity and biologists into the design process

Biodiversity provides a massive library of ideas for bio-inspired design, but the sheer number of species to consider can be daunting. Current approaches for sifting through biodiversity to identify relevant biological models include searching for champion adapters that are particularly adept at solving a particular design challenge. While the champion adapter approach has benefits, it tends to focus on a narrow set of popular models while neglecting the majority of species. An alternative approach to bio-inspired design is the comparative method, which leverages biodiversity by drawing inspiration across a broad range of species. This approach uses methods in phylogenetics to map traits across evolutionary trees and compare trait variation to infer structure-function relationships. Although comparative methods have not been widely used in bio-inspired design, they have led to breakthroughs in studies on gecko-inspired adhesives and multifunctionality of butterfly wing scales. Here we outline how comparative methods can be used to complement existing approaches to bioinspired design, and we provide an example focused on bio-inspired lattices, including honeycomb and glass sponges. We demonstrate how comparative methods can lead to breakthroughs in bio-inspired applications as well as answer major questions in biology, which can strengthen collaborations with biologists and produce deeper insights into biological function.

Antibacterial Honeycomb Scaffolds for Achieving Infection Prevention and Bone Regeneration

Surgical site infection (SSI) is a severe complication associated with orthopedic bone reconstruction. For both infection prevention and bone regeneration, the framework surface of osteoconductive and bioresorbable scaffolds must be locally modified by minimum antibacterial substances, without sacrificing the osteoconductivity of the scaffold framework. In this study, we fabricated antibacterial honeycomb scaffolds by replacing carbonate apatite, which is the main component of the scaffold, with silver phosphate locally on the scaffold surface via dissolution-precipitation reactions. When the silver content was 9.9 × 10^-4 wt %, the honeycomb scaffolds showed antibacterial activity without cytotoxicity and allowed cell proliferation, differentiation, and mineralization. Furthermore, the antibacterial honeycomb scaffolds perfectly prevented bacterial infection in vivo in the presence of methicillin-resistant Staphylococcus aureus, formed new bone at 2 weeks after surgery, and were gradually replaced with a new bone. Thus, the antibacterial honeycomb scaffolds achieved both infection prevention and bone regeneration. In contrast, severe infection symptoms, including abscess formation, osteolytic lesions, and inflammation, occurred 2 weeks after surgery when honeycomb scaffolds without silver phosphate modification were implanted. Nevertheless, the unmodified honeycomb scaffolds eliminated bacteria and necrotic bone through their scaffold channels, resulting in symptom improvement and bone formation. These results suggest that the honeycomb structure is inherently effective in hindering bacterial growth. This novel insight may contribute to the development of antibacterial scaffolds. Moreover, our modification method is useful for providing antibacterial activity to various biomaterials.

Magnetic dilution of a honeycomb lattice XY magnet CoTiO3

We report our study of cobalt (II) titanate, CoTiO₃, in which magnetic Co ions are replaced by non-magnetic ions. The antiferromagnetic ordering transition of CoTiO₃around 37 K is described with ferromagnetic honeycomb layers coupled antiferromagnetically along the crystallographicc-direction. The effect of magnetic dilution on the Néel temperature of this material is investigated through the doping of Zn²⁺and Mg²⁺in place of Co²⁺for various dilution levels up tox+y= 0.46 in Co_1-x-yZn_xMg_yTiO₃. Single phase polycrystalline samples have been synthesized and their structural and magnetic properties have been examined. A linear relation between dilution and the Néel temperature is observed over a wide doping range. A linear extrapolation would suggest that the required dilution level to suppress magnetic order is aroundx+y∼ 0.74, well beyond the classical percolation threshold. The implication of this observation for microscopic models for describing CoTiO₃is discussed.

Sound Insulation Performance of Composite Double Sandwich Panels with Periodic Arrays of Shunted Piezoelectric Patches

The existing sandwich structure of the aircraft cabin demonstrates a good sound insulation effect in medium and high frequency bands, but poor in the low frequency band. Therefore, we propose an infinite new lightweight broadband noise control structure and study its sound transmission loss (STL). The structure is an orthogonally rib-stiffened honeycomb double sandwich structure with periodic arrays of shunted piezoelectric patches, and demonstrates lighter mass and better strength than the existing sandwich structure. The structure is equivalent according to Hoff’s equal stiffness theory and the effective medium (EM) method. Using the virtual work principle for a periodic element, two infinite sets of coupled equations are obtained. They are solved by truncating them in a finite range until the solution converges. The correctness and validity of the model are verified by using simulation results and theoretical predictions. Eventually, a further study is performed on the factors influencing the STL. All the results demonstrate that the STL in low-frequency can be improved by the structure, and the sound insulation bandwidth is significantly broadened by adding shunted piezoelectric patches. The structure can provide a new idea for the design of broadband sound insulation.

Honeycomb Scaffold-Guided Bone Reconstruction of Critical-Sized Defects in Rabbit Ulnar Shafts

Reconstruction of critical-sized defects (CSDs) in bone shafts remains a major challenge in orthopedics. Honeycomb (HC) scaffolds are considered promising as their uniaxial channels bridge the amputation stumps of bones and promote the ingrowth of bone and blood vessels (BV) into the scaffolds. In this study, the ability of the HC scaffolds, composed of the bone mineral or carbonate apatite (CAp), was evaluated by reconstructing 10, 15, and 20 mm segmental defects in the rabbit ulnar shaft. Radiographic and μ-computed tomography evaluations showed that bony calluses were formed around the scaffolds at 4 weeks post-surgery in all defects, whereas no callus bridged in the ulna without scaffolds. At 12 weeks post-surgery, the scaffolds were connected to the host bone in 10 and 15 mm defects, while a slight gap remained between the scaffold and host bone in the 20 mm defect. New bone formation and scaffold resorption progressed over 12 weeks. Histological evaluations showed that mature bones (MB) and BV were already formed at the edges of the scaffolds at 4 weeks post-surgery in 10, 15, and 20 mm defects. In the central region of the scaffold, in the 10 mm defect, MB and BV were formed at 4 weeks post-surgery. In the 15 mm defect, although BV were formed, a few MB were formed. It is concluded that CAp HC scaffolds have good potential value for the reconstruction of CSDs.

Reconstruction of critical-size segmental defects in rat femurs using carbonate apatite honeycomb scaffolds

Critical-size segmental defects are formidable challenges in orthopedic surgery. Various scaffolds have been developed to facilitate bone reconstruction within such defects. Many previously studied scaffolds achieved effective outcomes with a combination of high cost, high-risk growth factors or stem cells. Herein, we developed honeycomb scaffolds (HCSs) comprising carbonate apatite (CO3 Ap) containing 8% carbonate, identical to human bone composition. The CO3 Ap HCSs were white-columned blocks harboring regularly arranged macropore channels of a size and wall thickness of 156 ± 5 μm and 102 ± 10 μm, respectively. The compressive strengths of the HCSs parallel and perpendicular to the macropore channel direction were 51.0 ± 11.8 and 15.6 ± 2.2 MPa, respectively. The HCSs were grafted into critical-sized segmental defects in rat femurs. The HCSs bore high-load stresses without any observed breakage. Two-weeks post-implantation, calluses formed around the HCSs and immature bone formed in the HCS interior. The calluses and immature bone matured until 8 weeks via endochondral ossification. At 12 weeks post-implantation, large parts of the HCSs were gradually replaced by newly formed bone. The bone reconstruction efficacy of the CO3 Ap HCSs alone was comparable to that of protein and cell scaffolds, while achieving a lower cost and increased safety.

Sandwich Structures for Energy Absorption Applications: A Review

It is crucial that proper engineering structures are designed as energy absorbers for high dynamic loading situations, such as accidents, blasts, or impacts. The role of such structures is to absorb the high kinetic energy as strain energy through irreversible deformation of the structure. Many types of energy absorbers were designed for different dynamic high strain rate applications. One of these structures are sandwich structures. The aim of this review paper is to provide a general review on the type of sandwich structures that have been designed as energy absorbers and their performance in crashworthiness and blast related applications. The focus is on the type of core structures being used, namely foam and architected cores. It was found from the review that sandwich structures are viable candidates for such applications not only because of their light weight, but also due to the high-energy absorption capabilities. The work presented in this review paper shows that the data from the literature on this topic are vast and do not converge to any particular sandwich structure design. This presents the potential future research direction in designing sandwich structures, which have wider application at different scales.

Carbonate apatite artificial bone

Bone apatite is not hydroxyapatite (HAp), it is carbonate apatite (CO3Ap), which contains 6-9 mass% carbonate in an apatitic structure. The CO3Ap block cannot be fabricated by sintering because of its thermal decomposition at the sintering temperature. Chemically pure (100%) CO3Ap artificial bone was recently fabricated through a dissolution-precipitation reaction in an aqueous solution using a precursor, such as a calcium carbonate block. In this paper, methods of fabricating CO3Ap artificial bone are reviewed along with their clinical and animal results. CO3Ap artificial bone is resorbed by osteoclasts and upregulates the differentiation of osteoblasts. As a result, CO3Ap demonstrates much higher osteoconductivity than HAp and is replaced by new bone via bone remodeling. Granular-type CO3Ap artificial bone was approved for clinical use in Japan in 2017. Honeycomb-type CO3Ap artificial bone is fabricated using an extruder and a CaCO3 honeycomb block as a precursor. Honeycomb CO3Ap artificial bone allows vertical bone augmentation. A CO3Ap-coated titanium plate has also been fabricated using a CaCO3-coated titanium plate as a precursor. The adhesive strength is as high as 76.8 MPa, with excellent tissue response and high osteoconductivity.

Computational Modeling of 2D Materials under High Pressure and Their Chemical Bonding: Silicene as Possible Field-Effect Transistor

To study the possibility for silicene to be employed as a field-effect transistor (FET) pressure sensor, we explore the chemistry of monolayer and multilayered silicene focusing on the change in hybridization under pressure. Ab initio computations show that the effect of pressure depends greatly on the thickness of the silicene film, but also reveals the influence of real experimental conditions, where the pressure is not hydrostatic. For this purpose, we introduce anisotropic strain states. With pure uniaxial stress applied to silicene layers, a path for sp³ silicon to sp³d silicon is found, unlike with pure hydrostatic pressure. Even with mixed-mode stress (in-plane pressure half of the out-of-plane one), we find no such path. In addition to introducing our theoretical approach to study 2D materials, we show how the hybridization change of silicene under pressure makes it a good FET pressure sensor.

Potential of Natural Fiber Reinforced Polymer Composites in Sandwich Structures: A Review on Its Mechanical Properties

The interest in using natural fiber reinforced composites is now at its highest. Numerous studies have been conducted due to their positive benefits related to environmental issues. Even though they have limitations for some load requirements, this drawback has been countered through fiber treatment and hybridization. Sandwich structure, on the other hand, is a combination of two or more individual components with different properties, which when joined together can result in better performance. Sandwich structures have been used in a wide range of industrial material applications. They are known to be lightweight and good at absorbing energy, providing superior strength and stiffness-to-weight ratios, and offering opportunities, through design integration, to remove some components from the core element. Today, many industries use composite sandwich structures in a range of components. Through good design of the core structure, one can maximize the strength properties, with a low density. However, the application of natural fiber composites in sandwich structures is still minimal. Therefore, this paper reviewed the possibility of using a natural fiber composite in sandwich structure applications. It addressed the mechanical properties and energy-absorbing characteristics of natural fiber-based sandwich structures tested under various compression loads. The results and potential areas of improvement to fit into a wide range of engineering applications were discussed.

Néel ordering in the distorted honeycomb pyrosilicate: C-Er2Si2O7

The rare-earth pyrosilicate family of compounds (RE2Si2O7) hosts a variety of polymorphs, some with honeycomb-like geometries of the rare-earth sublattices, and the magnetism has yet to be deeply explored in many of the cases. Here we report on the ground state properties of C-Er2Si2O7. C-Er2Si2O7crystallizes in the C2/m space group and the Er3+atoms form a distorted honeycomb lattice in thea-bplane. We have utilized specific heat, DC susceptibility, and neutron diffraction measurements to characterize C-Er2Si2O7. Our specific heat and DC susceptibility measurements show signatures of antiferromagnetic ordering at 2.3 K. Neutron powder diffraction confirms this transition temperature and the relative intensities of the magnetic Bragg peaks are consistent with a collinear Néel state in the magnetic space group C2'/m, with ordered moment of 6.61μBcanted 13° away from thec-axis toward thea-axis. These results are discussed in relation to the isostructural quantum dimer magnet compound Yb2Si2O7.

Experimental Analysis of Perimeter Shear Strength of Composite Sandwich Structures

The work concerns the experimental analysis of the process of destruction of sandwich structures as a result of circumferential shearing. The aim of the research was to determine the differences that occur in the destruction mechanism of such structures depending on the thickness and material of the core used. Specimens with a Rohacell foam core and a honeycomb core were made for the purposes of the research. The specimen destruction process was carried out in a static loading test with the use of a system introducing circumferential shear stress. The analysis of the tests results was made based on the load-displacement curves, the maximum load, and the energy absorbed by individual specimens. The tests indicated significant differences in the destruction mechanism of specimens with varied core material. The specimen with the honeycomb core was characterized by greater stiffness, which caused the damage to occur locally in the area subjected to the pressure of the punch. In specimens with the foam core, due to the lower stiffness of that core, the skins of the structure were bent, which additionally transfers compressive and tensile loads. This led to a higher maximum force that the specimens obtained at the time of destruction and greater energy absorption.

Defect Detection in Aerospace Sandwich Composite Panels Using Conductive Thermography and Contact Sensors

Sandwich panels consisting of two Carbon Fibre Reinforced Polymer (CFRP) outer skins and an aluminium honeycomb core are a common structure of surfaces on commercial aircraft due to the beneficial strength–weight ratio. Mechanical defects such as a crushed honeycomb core, dis-bonds and delaminations in the outer skins and in the core occur routinely under normal use and are repaired during aerospace Maintenance, Repair and Overhaul (MRO) processes. Current practices rely heavily on manual inspection where it is possible minor defects are not identified prior to primary repair and are only addressed after initial repairs intensify the defects due to thermal expansion during high temperature curing. This paper reports on the development and characterisation of a technique based on conductive thermography implemented using an array of single point temperature sensors mounted on one surface of the panel and the concomitant induced thermal profile generated by a thermal stimulus on the opposing surface to identify such defects. Defects are classified by analysing the differential conduction of thermal energy profiles across the surface of the panel. Results indicate that crushed core and impact damage are detectable using a stepped temperature profile of 80 ∘C The method is amenable to integration within the existing drying cycle stage and reduces the costs of executing the overall process in terms of time-to-repair and manual effort.

Bioinspired Honeycomb Core Design: An Experimental Study of the Role of Corner Radius, Coping and Interface

The honeybee’s comb has inspired the design of engineering honeycomb core that primarily abstract the hexagonal cell shape and exploit its mass minimizing properties to construct lightweight panels. This work explored three additional design features that are part of natural honeybee comb but have not been as well studied as design features of interest in honeycomb design: the radius at the corner of each cell, the coping at the top of the cell walls, and the interface between cell arrays. These features were first characterized in natural honeycomb using optical and X-ray techniques and then incorporated into honeycomb core design and fabricated using an additive manufacturing process. The honeycomb cores were then tested in out-of-plane compression and bending, and since all three design features added mass to the overall structure, all metrics of interest were examined per unit mass to assess performance gains despite these additions. The study concluded that the presence of an interface increases specific flexural modulus in bending, with no significant benefit in out-of-plane compression; coping radius positively impacts specific flexural strength, however, the corner radius has no significant effect in bending and actually is slightly detrimental for out-of-plane compression testing.

p Orbital Flat Band and Dirac Cone in the Electronic Honeycomb Lattice

Theory anticipates that the in-plane px, py orbitals in a honeycomb lattice lead to potentially useful quantum electronic phases. So far, p orbital bands were only realized for cold atoms in optical lattices and for light and exciton-polaritons in photonic crystals. For electrons, in-plane p orbital physics is difficult to access since natural electronic honeycomb lattices, such as graphene and silicene, show strong s-p hybridization. Here, we report on electronic honeycomb lattices prepared on a Cu(111) surface in a scanning tunneling microscope that, by design, show (nearly) pure orbital bands, including the p orbital flat band and Dirac cone.

Mechanical Properties of Corner Joints Made of Honeycomb Panels with Double Arrow-Shaped Auxetic Cores

The development of both light and strong wood-derived materials is an interesting research area, particularly in terms of usability in, e.g., furniture constructions. Honeycomb panels being current industry standard are relatively thick (32 mm and 40 mm), thus their attractiveness in designing furniture is limited. In a few studies, it has been shown that honeycomb panels with paper cores are characterized by unsatisfactory mechanical properties, especially when the composite thickness is less than 20 mm. From the literature, it is also evident that mechanical properties might be improved by introducing auxetic features into the core structure. Even though it is a concept with great potential, there are a few studies dealing with honeycomb panels with auxetic cores made of paper. Furthermore, there is no research on the corner joints made from such material. For this reason, the aim of the study was to test the bending behavior of the corner adhesive joints made of honeycomb panels with double arrow-shaped auxetic cores. Within the research, the core cell was adopted based on literature and preliminary studies, paper auxetic cores were produced by the use of the designed and 3d printed device, and joints stiffness and strength were calculated analytically based on the experiment results. Evaluated corner joints stiffness, both in compression and tension test, is greater for samples made of panels with designed auxetic cores. Surprisingly, in the analyzed range of elasticity, it was statistically proved that the values of joint stiffness coefficient K did not vary significantly between compared joints pairs.

Switchable Isotropic/Anisotropic Wettability and Programmable Droplet Transportation on a Shape-Memory Honeycomb

Programmable droplet transportation is required urgently but is still challenging. In this work, breath figure was employed to fabricate shape-memory poly(lactic acid) (PLLA) honeycombs in which tiny crystals and an amorphous network act as the shape-fixed phase and recovery phase, respectively. Upon uniaxial tension, circle pores from the breath figure were deformed to elliptical pores, producing contact angle differences and anisotropic wetting behaviors in two directions. Both pore geometry and anisotropic wettability can be tailored via the draw ratio. On the PLLA honeycomb surface with a lower draw ratio, the contact angle difference is too small to induce droplet transportation along the desired direction. In the case of a higher draw ratio, however, the movement of water droplets has been controlled absolutely along the tension direction. The transition between them can be achieved reversibly during uniaxial tension and recovery processes based on the shape-memory effect. The enhanced flow control, which can be attributed to the synergism between optimal hydrophobicity and enlarged anisotropic wetting behaviors, endows water droplets with the ability to turn a corner spontaneously on a V-shaped surface including two regions exhibiting different oriented directions.

The combination of a poly-caprolactone/nano-hydroxyapatite honeycomb scaffold and mesenchymal stem cells promotes bone regeneration in rat calvarial defects

Bone tissue engineering goes beyond the limitations of conventional methods of treating bone loss, such as autograft-induced morbidity and a lack of integration for large grafts. Novel biomimicry approaches (using three-dimensional [3D] electrospinning and printing techniques) have been designed to offer the most appropriate environment for cells and thus promote bone regeneration. In the present study, we assessed the bone regeneration properties of a composite 3D honeycomb structure from the electrostatic template-assisted deposition process by an alternate deposition of electrospun polycaprolactone (PCL) nanofibers and electrosprayed hydroxyapatite nanoparticles (nHA) on a honeycomb micropatterned substrate. We first confirmed the cytocompatibility of this honeycomb PCL-nHA scaffold in culture with bone marrow-derived mesenchymal stem cells (BM-MSCs). The scaffold was then implanted (alone or with seeded MSCs) for 2 months in a rat critical-sized calvarial defect model. The observation of new bone synthesis in situ (monitored using microcomputed tomography every 2 weeks and a histological assessment upon extraction) demonstrated that the honeycomb PCL-nHA scaffold was osteoconductive. Moreover, the combination of the scaffold with BM-MSCs was associated with significantly greater bone volume and mineralized regeneration during the 2-month experiment. The combination of the biomimetic honeycomb PCL-nHA scaffold with patient mesenchymal stem cells might therefore have great potential for clinical applications and specifically in maxillofacial surgery.

Effect of Absorbent Foam Filling on Mechanical Behaviors of 3D-Printed Honeycombs

Polylactic acid (PLA) hexagonal honeycomb structures were fabricated by using 3D-printing technology. By filling with absorbent polymethacrylimide (PMI) foam, a novel absorbent-foam-filled 3D-printed honeycomb was obtained. The in-plane (L- and W-direction) and out-of-plane (T-direction) compressive performances were studied experimentally and numerically. Due to absorbent PMI foam filling, the elastic modulus, compressive strength, energy absorption per unit volume, and energy absorption per unit mass of absorbent-foam-filled honeycomb under L-direction were increased by 296.34%, 168.75%, 505.57%, and 244.22%, respectively. Moreover, the elastic modulus, compressive strength, energy absorption per unit volume, and energy absorption per unit mass, under W-direction, also have increments of 211.65%, 179.85, 799.45%, and 413.02%, respectively. However, for out-of-plane compression, the compressive strength and energy absorption per unit volume were enhanced, but the density has also been increased; thus, it is not competitive in energy absorption per unit mass. Failure mechanism and dimension effects of absorbent-foam-filled honeycomb were also considered. The approach of absorbent foam filling made the 3D-printed honeycomb structure more competitive in electromagnetic wave stealth applications, while acting simultaneously as load-carrying structures.

Electromagnetic Wave Absorption Properties of Structural Conductive ABS Fabricated by Fused Deposition Modeling

To obtain excellent electromagnetic wave (EMW) absorption materials, the design of microstructures has been considered as an effective method to adjust EMW absorption performance. Owing to its inherent capability of effectively fabricating materials with complex various structures, three-dimensional (3D) printing technology has been regarded as a powerful tool to design EMW absorbers with plentiful microstructures for the adjustment of EMW absorption performance. In this work, five samples with various microstructures were prepared via fused deposition modeling (FDM). An analysis method combining theoretical simulation calculations with experimental measurements was adopted to investigate EMW absorbing properties of all samples. The wood-pile-structural sample possessed wider effective absorption bandwidth (EAB; reflection loss (RL) <−10 dB, for over 90% microwave absorption) of 5.43 GHz and generated more absorption bands (C-band and Ku-band) as compared to the honeycomb-structural sample at the same thickness. Designing various microstructures via FDM proved to be a convenient and feasible method to fabricate absorbers with tunable EMW absorption properties, which provides a novel path for the preparation of EMW absorption materials with wider EAB and lower RL.

Experimental Research and Numerical Analysis of the Elastic Properties of Paper Cell Cores before and after Impregnation

The research hypothesis states that the impregnation of the honeycomb paper core of lightweight sandwich panels with modified starch, sodium silicate and epoxy resin (LiquidWood^®) resin has a significant effect on its elastic properties. In this study, a recycled paper was used in three thicknesses, seven types of cell shapes, including two after numerical optimization and three types of impregnating agents. The method of digital image analysis determined the elastic constants of manufactured paper cores, which were subjected to axial compression in two directions. Based on the experimental results, elastic constants of the cores were calculated and compared with the results of numerical calculations. It has been shown that each of the impregnating solutions used improved the stiffness of the paper core. The best results were obtained for LiquidWood^® epoxy resin and modified starch. An important parameter of cell geometry affecting their rigidity is the angle of the cell wall φ, as well as the arrangement of the common cell wall in relation to the direction of load. The numerical models developed were positively verified.

Analytical Scheme for Simultaneous Determination of Phthalates and Bisphenol A in Honey Samples Based on Dispersive Liquid-Liquid Microextraction Followed by GC-IT/MS. Effect of the Thermal Stress on PAE/BP-A Levels

In this paper, an analytical protocol was developed for the simultaneous determination of phthalates (di-methyl phthalate DMP, di-ethyl phthalate DEP, di-isobutyl phthalate DiBP, di-n-butyl phthalate DBP, bis-(2-ethylhexyl) phthalate DEHP, di-n-octyl phthalate DNOP) and bisphenol A (BPA). The extraction technique used was the ultrasound vortex assisted dispersive liquid–liquid microextraction (UVA-DLLME). The method involves analyte extraction using 75 µL of benzene and subsequent analysis by gas chromatography combined with ion trap mass spectrometry (GC-IT/MS). The method is sensitive, reliable, and reproducible with a limit of detection (LOD) below 13 ng g⁻¹ and limit of quantification (LOQ) below 22 ng g⁻¹ and the intra- and inter-day errors below 7.2 and 9.3, respectively. The method developed and validated was applied to six honey samples (i.e., four single-use commercial ones and two home-made ones. Some phthalates were found in the samples at concentrations below the specific migration limits (SMLs). Furthermore, the commercial samples were subjected to two different thermal stresses (24 h and 48 h at 40 °C) for evidence of the release of plastic from the containers. An increase in the phthalate concentrations was observed, especially during the first phase of the shock, but the levels were still within the limits of the regulations.

A Unidirectional Soft Dielectric Elastomer Actuator Enabled by Built-In Honeycomb Metastructures

Dielectric elastomer actuators (DEAs) are able to undergo large deformation in response to external electric stimuli and have been widely used to drive soft robotic systems, due to their advantageous attributes comparable to biological muscles. However, due to their isotropic material properties, it has been challenging to generate programmable actuation, e.g., along a predefined direction. In this paper, we provide an innovative solution to this problem by harnessing honeycomb metastructures to program the mechanical behavior of dielectric elastomers. The honeycomb metastructures not only provide mechanical prestretches for DEAs but, more importantly, transfer the areal expansion of DEAs into directional deformation, by virtue of the inherent anisotropy. To achieve uniaxial actuation and maximize its magnitude, we develop a finite element analysis model and study how the prestretch ratios and the honeycomb structuring tailor the voltage-induced deformation. We also provide an easy-to-implement and scalable fabrication solution by directly printing honeycomb lattices made of thermoplastic polyurethane on dielectric membranes with natural bonding. The preliminary experiments demonstrate that our designed DEA is able to undergo unidirectional motion, with the nominal strain reaching up to 15.8%. Our work represents an initial step to program deformation of DEAs with metastructures.

An Examination of the Low Strain Rate Sensitivity of Additively Manufactured Polymer, Composite and Metallic Honeycomb Structures

The characterization of additively manufactured cellular materials, such as honeycombs and lattices, is crucial to enabling their implementation in functional parts. One of the characterization methods commonly employed is mechanical testing under compression. This work focuses specifically on the dependence of these tests to the applied strain rate during the test over low strain rate regimes (considered here as 10⁻⁶ to 10⁻¹ s⁻¹). The paper is limited to the study of strain the rate dependence of hexagonal honeycomb structures manufactured with four different additive manufacturing processes: one polymer (fused deposition modeling, or material extrusion with ABS), one composite (nylon and continuous carbon fiber extrusion) and two metallic (laser powder bed fusion of Inconel 718 and electron beam melting of Ti6Al4V). The strain rate sensitivities of the effective elastic moduli, and the peak loads for all four processes were compared. Results show significant sensitivity to strain rate in the polymer and composite process for both these metrics, and mild sensitivity for the metallic honeycombs for the peak load. This study has implications for the characterization and modeling of all mechanical cellular materials and makes the case for evaluation and if appropriate, inclusion, of strain rate effects in all cellular material modeling.

3D Honeycomb Architecture Enables a High-Rate and Long-Life Iron (III) Fluoride-Lithium Battery

Metal fluoride-lithium batteries with potentially high energy densities, even higher than lithium-sulfur batteries, are viewed as very promising candidates for next-generation lightweight and low-cost rechargeable batteries. However, so far, metal fluoride cathodes have suffered from poor electronic conductivity, sluggish reaction kinetics and side reactions causing high voltage hysteresis, poor rate capability, and rapid capacity degradation upon cycling. Herein, it is reported that an FeF₃ @C composite having a 3D honeycomb architecture synthesized by a simple method may overcome these issues. The FeF₃ nanoparticles (10-50 nm) are uniformly embedded in the 3D honeycomb carbon framework where the honeycomb walls and hexagonal-like channels provide sufficient pathways for the fast electron and Li-ion diffusion, respectively. As a result, the as-produced 3D honeycomb FeF₃ @C composite cathodes even with high areal FeF₃ loadings of 2.2 and 5.3 mg cm^-2 offer unprecedented rate capability up to 100 C and remarkable cycle stability within 1000 cycles, displaying capacity retentions of 95%-100% within 200 cycles at various C rates, and ≈85% at 2C within 1000 cycles. The reported results demonstrate that the 3D honeycomb architecture is a powerful composite design for conversion-type metal fluorides to achieve excellent electrochemical performance in metal fluoride-lithium batteries.

Four Questions in Cellular Material Design

The design of cellular materials has recently undergone a paradigm shift, enabled by developments in Additive Manufacturing and design software. No longer do cellular materials have to be limited to traditional shapes such as honeycomb panels or stochastic foams. With this increase in design freedom comes a significant increase in optionality, which can be overwhelming to the designer. This paper aims to provide a framework for thinking about the four key questions in cellular material design: how to select a unit cell, how to vary cell size spatially, what the optimal parameters are, and finally, how best to integrate a cellular material within the structure at large. These questions are posed with the intent of stimulating further research that can address them individually, as well as integrate them in a systematic methodology for cellular material design. Different state-of-the-art solution approaches are also presented in order to provoke further investigation by the reader.

Prevalence and diagnostic value of the ultrasonographic honeycomb appearance of the spleen in cats

Objectives

The aim of this study was to report the prevalence of a honeycomb appearance of the spleen in a population of referral cats presented for ultrasound examination, and to determine the diagnostic value of this finding vs the definitive diagnosis, the splenic cytological and haematological results.

Methods

Data were obtained from the medical records (2016–2018) of cats that had an ultrasonographic honeycomb appearance of the spleen, a splenic cytological diagnosis and a complete blood count.

Results

Twenty-five cats were included. Prevalence of the honeycomb pattern was 6.8%. None of the spleen was considered normal on cytology and four types of lesions were found: lymphoid hyperplasia (64%), neoplasia (16%), extramedullary haematopoiesis (12%) and splenitis (8%). A honeycomb pattern was successfully identified with a linear high-frequency probe in all cats, but only in 36% of cases with the micro-convex probe. Follow-up information was available for four cats, in which the honeycomb appearance persisted up to 105 days after the first examination; there was persistence of the honeycomb pattern in all cases. Cats with a splenic cytological diagnosis of extramedullary haematopoiesis had the lowest haemoglobin plasma concentration (P = 0.011).

Conclusions and relevance

Honeycomb appearance of the spleen is uncommon in cats and, in our study, was systematically associated with cytological alterations; most of the time it was benign (84%). The use of a high-frequency linear probe improves its detection rate. No epidemiological, ultrasonographic or clinical criteria allow differentiation between the different types of infiltration and fine-needle aspiration is therefore recommended.

Fabrication of carbonate apatite honeycomb and its tissue response

Carbonate apatite (CO₃ Ap) block can be used as a bone substitute because it can be remodeled to new natural bone in a manner conforming with the bone remodeling process. Among the many porous structures available, honeycomb (HC) structure is advantageous for rapid replacement of CO₃ Ap to bone. In this study, the feasibility to fabricate a CO₃ Ap HC was studied, along with its initial tissue response in rabbit femur bone defect. First, a mixture of Ca(OH)₂ and a wax-based binder was extruded from a HC mold. Then the fabricated HC was heated for binder removal and carbonation at 450°C in a mixed O₂ -CO₂ atmosphere, forming a CaCO₃ HC. When the CaCO₃ HC was immersed in 1 mol/L Na₃ PO₄ solution at 80°C for 7 days, its composition changed from CaCO₃ to CO₃ Ap, maintaining the structure of the original CaCO₃ HC. Compressive strengths of the CaCO₃ and CO₃ Ap HCs were 65.2 ± 7.4 MPa and 88.7 ± 4.7 MPa, respectively. When the rabbit femur bone defect was reconstructed with the CO₃ Ap HC, new bone penetrated the CO₃ Ap HC completely. Osteoclasts and osteoblasts were found on the surface of the newly formed bone and osteocytes were also found in the newly formed bone, indicating ongoing bone remodeling. Furthermore, blood vessels were formed inside the pores of CO₃ Ap HC. Therefore, CO₃ Ap HC has good potential as an ideal bone substitute. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 1014-1020, 2019.

The Effect of the Isomeric Chlorine Substitutions on the Honeycomb-Patterned Films of Poly(x-chlorostyrene)s/Polystyrene Blends and Copolymers via Static Breath Figure Technique

Polymeric thin films patterned with honeycomb structures were prepared from poly(x-chlorostyrene) and statistical poly(x-chlorostyrene-co-styrene) copolymers by static breath figure method. Each polymeric sample was synthesized by free radical polymerization and its solution in tetrahydrofuran cast on glass wafers under 90% relative humidity (RH). The effect of the chorine substitution in the topography and conformational entropy was evaluated. The entropy of each sample was calculated by using Voronoi tessellation. The obtained results revealed that these materials could be a suitable toolbox to develop a honeycomb patterns with a wide range of pore sizes for a potential use in contact guidance induced culture.