Foam-like Structure Research Articles

Natural Plant Materials as Dielectric Layer for Highly Sensitive Flexible Electronic Skin.

Nature has long offered human beings with useful materials. Herein, plant materials including flowers and leaves have been directly used as the dielectric material in flexible capacitive electronic skin (e-skin), which simply consists of a dried flower petal or leaf sandwiched by two flexible electrodes. The plant material is a 3D cell wall network which plays like a compressible metamaterial that elastically collapses upon pressing plus some specific surface structures, and thus the device can sensitively respond to pressure. The device works over a broad-pressure range from 0.6 Pa to 115 kPa with a maximum sensitivity of 1.54 kPa-1 , and shows high stability over 5000 cyclic pressings or bends. The natural-material-based e-skin has been applied in touch sensing, motion monitoring, gas flow detection, and the spatial distribution of pressure. As the foam-like structure is ubiquitous in plants, a general strategy for a green, cost-effective, and scalable approach to make flexible e-skins is offered here.

Дослідження піноподібної структури безглютенового бездріжджового тіста з використанням гідроколоїдів та концентратів тваринних білків

Дослідження піноподібної структури безглютенового бездріжджового тіста з використанням гідроколоїдів та концентратів тваринних білків

Preliminary assessment of methanogenic microbial communities in marine caves of Zakynthos Island (Ionian Sea, Greece)

Mediterranean marine caves remain largely unexplored, while particularly limited information is available about the microbial life existing in these unique environments. The present study is a preliminary assessment of the composition of the active anaerobic microbial community colonizing the walls of newly explored systems of underwater caves and small cavities in Zakynthos Island. The interior of these caves is densely coated with egg-shaped, foam-shaped and filamentous biological structures that are characterised by a strong odor of hydrogen sulfide gas. A total of twelve structures scrapped from cave rocks were subjected to anaerobic cultivation for up to 208 days. Strong to moderate methanogenesis was observed in two different types of egg-shaped structures and one foam-like structure. Interestingly, this was observed in experiments that were performed at room temperature (i.e. 25oC) which is substantially lower than those typically considered optimum for methane production (e.g. 35oC). Analysis of the 16S rRNA genes revealed a clear dominance of archaea and bacteria closely related to known methane producers and sulfate reducers, including members of the families Methanomicrobiaceae, Desulfobulbaceae, Desulfobacteraceae, Desulfuromonaceae, Campylobacteraceae, Marinifilaceae, Clostridiaceae, Incertae Sedis – Family I & II. These results show that Mediterranean marine caves can host members of archaea and bacteria with potential biotechnological interest that deserve further investigation.

Ceramic light-weight aggregates production from petrochemical wastes and carbonates (NaHCO3 and CaCO3) as expansion agents

This work shows the production of a ceramic light-weight aggregate (LWA) from mixtures of petrochemical wastes (oily wastes and oil sludge), a conventional clay and two different carbonates (NaHCO3 and CaCO3) used as expansion agents. The novelty of this study is the valorization of an important hazardous waste for the synthesis of a potential material for construction. All these feedstock where characterized by elemental, proximate and TG/DTG analyses and also by XRF for determining the inorganic composition. The LWA were produced from two different mixtures: i) clay and oily waste (CW) and ii) clay and oil sludge (CS), by using different proportions of both NaHCO3 and CaCO3 (0, 20 and 40 wt%). Additionally, the influence of sintering temperature (900, 950 and 1000 °C) on the particle density was also evaluated. Although TG/DTG analysis suggests a higher CO2 release with CaCO3 and hence, a higher bloating phenomena; there also appears an influence of the petrochemical waste composition. In addition, the particle density varied from 1.394 to 2.227 g/cm3, and from 1.226 to 2.571 g/cm3, for mixtures using CaCO3 and NaHCO3, respectively, and the lower the sintering temperature, the lower the particle density. The lowest density (1.223 g/cm3) was obtained when oily waste and NaHCO3 at 40 wt% are used (CW_NaHCO3_40). For this mixture, the synthesis process is prompted not only by the NaHCO3 addition, but also by the reaction among different elements of clay and oily waste. The resulting aggregate exhibited a foam-like structure with rounded cavities, suggesting the bloating phenomenon occurrence.

Efficient visible-light-driven depolymerization of oxidized lignin to aromatics catalyzed by an iridium complex immobilized on mesocellular silica foams

A novel Ir(ppy)2(bpy) complex-containing mesoporous cellular silica foams (Ir(ppy)2(bpy)-MCFs) was prepared by a facile thiol-ene click reaction between the prefabricated thiol-functionalized mesoporous cellular silica foams and vinyl-tagged [Ir(ppy)2(bpy)]PF6 complex. The elaborate Ir(ppy)2(bpy)-MCFs material possessed the large surface area (355 cm2/g), open foam-like mesoporous structure with 30 nm cell pore size and 3.0 nm window pore size. Importantly, it had the well-defined molecular configuration of Ir(ppy)2(bpy) active species. As expected, it exhibited excellent catalytic reactivity and selectivity in the visible-light-driven reductive depolymerization of oxidized lignin β-O-4 model compounds including p-hydroxyphenyl (H)-, guaiacyl (G)- and syringyl (S)-type units under the mild conditions. Meanwhile, it showed the comparable catalytic efficiency with the corresponding homogeneous [Ir(ppy)2(bpy)]PF6 catalyst. These high catalytic performances could be attributed to aerogel-like three-dimensional pore structure and high visible-light transparency, which efficiently decreased the mass transfer resistance and the photon propagation hindrance. Furthermore, it could be easily recycled and reused at least six times without the remarkable loss of catalytic activity.

One-Step Fast-Synthesized Foamlike Amorphous Co(OH)2 Flexible Film on Ti Foil by Plasma-Assisted Electrolytic Deposition as a Binder-Free Anode of a High-Capacity Lithium-Ion Battery.

This research prepared an amorphous Co(OH)2 flexible film on Ti foil using plasma-assisted electrolytic deposition within 3.5 min. Amorphous Co(OH)2 structure was determined by X-ray diffraction and X-ray photoelectron spectroscopy. Its areal capacity testing as the binder and adhesive-free anode of a lithium-ion battery shows that the cycling capacity can reach 2000 μAh/cm2 and remain at 930 μAh/cm2 after 50 charge-discharge cycles, which benefits from the emerging Co(OH)2 active material and amorphous foamlike structure. The research introduced a new method to synthesize amorphous Co(OH)2 as the anode in a fast-manufactured low-cost lithium-ion battery.

Modulation of the mechanical, physical and chemical properties of polyvinylidene fluoride scaffold via non-solvent induced phase separation process for nerve tissue engineering applications

The aim of this research was to develop microporous poly(vinylidene fluoride) (PVDF) scaffolds with an intrinsic electrical property, via the combination of non-solvent induced phase separation (NIPS) and thermal induced phase separation (TIPS) process referred as N-TIPS method. For this purpose, the effects of non-solvent incorporation (distilled water) in the solvent composition (N,N-dimethylformamide (DMF)), immersion time at coagulation bath (1, 3, 6 and 24 h) as well as coagulation bath temperature (−10, 0 and 20 °C) and composition (DMF:water volume ratio = 2:6 and 6:4) on the properties of the produced scaffolds were investigated. Results confirmed that N-TIPS processing parameters had a profound effect on the morphological, mechanical, physical and thermal properties of the PVDF scaffolds. For instance, with increased bath temperature, the formation of three-dimensional bi-continuous scaffold with average pore size of 4.2 ± 0.6 μm was achieved, whereas increase in the immersion time in coagulation bath from 1 to 24 h induced cellular morphology with a larger pore size. The formation of relatively small pore size and uniform foam-like structure at 3 h soaking in coagulation bath showed to improved mechanical properties of the scaffolds. It was also found that toughness of the scaffolds significantly promoted from 27.5 ± 16.4 MPa (after 1 h soaking) to 155.2 ± 25.4 MPa (after 3 h soaking). Moreover, depending on the functional parameters of N-TIPS process, β phase fraction and crystallinity of the PVDF scaffolds were in the range of 61–87% and 30–47%, respectively. Remarkably, 3 h soaking of PVDF polymer solution in coagulation bath with composition of 6:4 (D-3h-64 scaffold) significantly enhanced the crystallinity (47.03%) and β phase fraction (87.9%) and reduced crystallite size of PVDF polymer. The PC12 cell attachment and proliferation on PVDF scaffolds prepared at various parameters were also investigated. Noticeably, D-3h-64 scaffold with enhanced crystallinity and β phase fraction and significantly higher toughness could promote cell spreading and proliferation. The results presented in this study show a great potential of PVDF scaffolds with desired properties for nerve tissue engineering application.

Transition metal assisted synthesis of tunable pore structure carbon with high performance as sodium/lithium ion battery anode

Template method has been used as an important method to prepare porous materials. However, there are few reports about template method employing potassium chloride as template. Here, potassium chloride is employed as a template to prepare the porous carbon, and transition metal nitrates (Fe(NO3)2,d Co(NO3)2, Ni(NO3)2) are introduced to catalyze graphitization and to result different carbon structure during carbonization (denoted as Fe@C, Co@C and Ni@C). The Fe@C shows a formicary-like structure with an about 20 nm pore diameter and the Co@C displays a completely compact structure. Whereas, the Ni@C exhibits a foam-like structure with hierarchical porous structure consisting of macroporous frameworks, mesopores and ultrathin porous walls (∼5 nm). Its macropore and mesopore diameter is around 100 nm and 4 nm, respectively, its specific surface area is 464.5 m2 g−1. When adopted as anode material, the Ni@C presents much outstanding rate and cycling capability for lithium and sodium storage than Fe@C and Co@C, the capacity for sodium storage is 260 mAh g−1 after 100 cycles at 100 mA g−1 and 92 mAh g−1 after 1000 cycles at 1A g−1, and the capacity for lithium storage is 683 mAh g−1 after 1000 cycles at a current density of 1 A g−1.

Preparation of poly(lactic acid)/sintered hydroxyapatite composite biomaterial by supercritical CO2.

Based on a kind of sintered hydroxyapatite (HA) with a good cytocompatibility, a series of polylactic acid (PLA) and PLA/HA with the various PLA:HA weight ratio (5:5, 4:6, 3:7, 2:8, 1:9) were fabricated by supercritical CO2. The physical and chemical properties were evaluated by pH, degradation, water absorption, porosity, density, mechanical property, and cytotoxicity respectively. With the increase of HA content, the pH value and porosity increased gradually, while weight loss rate and the density showed a gradual downward trend. Existence of HA can drastically improve the hydroscopicity of PLA scaffolds. The compression strength values slightly increased (p>0.05) from 39.96MPa of PLA to 45.00MPa of PLA/HA with the ratio of 7:3, subsequently, the values decreased (p<0.05) from 43.29MPa (8:2) to 19.00MPa (9:1). While the modulus of elasticity decreased (p<0.05) from 5.89 to 1.84GPa with increasing HA content. The PLA/HA (8:2) promoted cell proliferation more significantly than any of other groups (p<0.05). Based on the results, the overall properties of porous scaffolds are the optimal when the weight ratio of PLA/HA is 8:2. Its pH, porosity, density, compression strength, and elasticity modulus are 7.39, 83.0%, 0.60g/cm-3, 34.1MPa and 2.63GPa, respectively. SEM observation presented a homogeneous distribution of HA in PLA matrix and a foam-like structure comprising interconnected pores.

Transparent, abrasion-insensitive superhydrophobic coatings for real-world applications

Superhydrophobic surfaces and surface coatings are of high interest for many applications in everyday life including non-wetting and low-friction coatings as well as functional clothing. Manufacturing of these surfaces is intricate since superhydrophobicity requires structuring of surfaces on a nano- to microscale. This delicate surface structuring makes most superhydrophobic surfaces very sensitive to abrasion and renders them impractical for real-life applications. In this paper we present a transparent fluorinated polymer foam that is synthesized by a simple one-step photoinitiated radical polymerization. We term this material “Fluoropor”. It possesses an inherent nano-/microstructure throughout the whole bulk material and is thus insensitive to abrasion as its superhydrophobic properties are not merely due to a thin-layer surface-effect. Due to its foam-like structure with pore sizes below the wavelength of visible light Fluoropor appears optically transparent. We determined contact angles, surface energy, wear resistance and Vickers hardness to highlight Fluoropor’s applicability for real-word applications.

X-ray Reflectivity Studies on the Mixed Langmuir-Blodgett Monolayers of Thiol-Capped Gold Nanoparticles, Dipalmitoylphosphatidylcholine, and Sodium Dodecyl Sulfate.

Langmuir-Blodgett monolayers of thiolated gold nanoparticles mixed with dipalmitoylphosphatidylcholine/sodium dodecyl sulfate (DPPC/SDS) were investigated by combining the X-ray reflectivity, grazing-incident scattering, and TEM analyses to reveal the in-depth and in-plane organization and the 2D morphology of such mixed monolayers. It was found that the addition of a charged single-tail surfactant to the thiolated Au nanoparticle monolayer helps to stabilize the Au nanoparticle monolayer and to strengthen the mechanical property of the mixed monolayer film. For mixing with lipids, it was found that the thiolated gold nanoparticles could be pushed on top of the lipid monolayer when the mixed monolayer is compressed. At a typical comparable total surface area ratio of gold nanoparticle to lipid, the thiolated gold nanoparticles could form a uniform domain on top of the DPPC monolayer. When there are more thiolated gold nanoparticles than that could be supported by the lipid monolayer, domain overlapping could occur to form bilayer gold nanoparticle domains at some regions. At low total surface area ratio of thiolated gold nanoparticle to lipid, the thiolated gold nanoparticles tend to form a connected threadlike aggregation structure. Evidently, the morphology of the thiolated gold nanoparticle monolayer is highly depending on the total surface area ratio of the thiolated gold nanoparticle to lipid. SDS is found to have a dispersion power capable of dispersing the originally uniform Au-8C nanoparticle domain of the mixed Au-8C/DPPC monolayer into a foamlike structure for the mixed Au-8C/SDS/DPPC monolayer. It is evident that not only the concentration ratio but also the size and shape of the template formed by the amphiphilic molecules and their interaction with the thiolated gold nanoparticles can all have great effects on the organizational structure as well as morphology of the thiolated gold nanoparticle monolayer.

Study of the interaction between molten indium and sub-atmospheric pressure hydrogen glow discharge for low-temperature nanostructured metallic particle film deposition

Indium (In) evaporation is enhanced by high-pressure hydrogen glow plasma, and a sponge-like In film containing submicron pores is prepared on the substrate. The glow plasma is generated at a total pressure of 13.3 kPa (100 Torr) as a capacitively coupled plasma. When the process atmosphere is diluted by He and Ar, the In evaporation rate increases by increasing the hydrogen concentration and no evaporation is observed without H2 gas. The In deposition rate exhibits no dependence on the In temperature in the range from 300 °C to 600 °C. However, the In deposition rate increases linearly by increasing the input power. The obtained deposition rate reaches 7.5 mg/s with an input power of 800 W even at an In temperature of 450 °C. The obtained weight deposition rate is equivalent to the thickness deposition rate of 1.6 μm/s. The prepared In film on the Si substrate is composed of a porous foam-like structure. The particle diameter distributes from 40 nm to a few tens of micrometers. The particles with diameters above a few micrometers reveal a porous structure with a pore size of less than 100 nm. The obtained In film consists of crystalline In. Thermal desorption measurements of the prepared In film reveal that a large amount of H2 gas is confined in the In film relative to the hydrogen solubility in solid In. The obtained results suggest that the excess hydrogen solubility in the liquid metal induced by H2 plasma is an important factor for the enhancement of In evaporation.

One-Pot Synthesis of Biomass-Based Hierarchical Porous Carbons with a Large Porosity Development

A sustainable one-pot scheme for the synthesis of hierarchical porous carbons formed from biomass is developed herein. It is based on the carbonization of biomass-derived products (glucose, glucosamine, soya flour, and microalgae) in the presence of an activating agent (potassium oxalate) and calcium carbonate nanoparticles that form a hard template. During carbonization, double carbonates are formed in situ, which results in modifications in the morphology and size of the template nanoparticles, giving rise to a carbon material with an open macroporous foam-like structure rich in micro-/mesopores, the latter developing via a redox reaction between the carbon and potassium carbonate and also as a result of the reaction between the carbon and the evolved CO2. The porosity can be tailored by selecting an appropriate precursor. Thus, the carbon materials are basically micro-/macroporous in the case of glucose and glucosamine, and micro-/meso-/macroporous when soya flour and microalgae are used. A direct rela...

Facile synthesis of bicontinuous Ni3Fe alloy for efficient electrocatalytic oxygen evolution reaction

Oxygen evolution reaction is a vital aspect of several energy generation technologies such as water splitting, metal air batteries. However, unreceptive thermodynamics and slothful kinetics of this process mandate the use of a noble metal catalyst. Substituting these noble metals by more abundant transition metals is vital for commercial application of these technologies. In this regard, we have developed a facile method for synthesis of Ni3Fe alloy with bicontinuous structure. The highly porous foam-like structure of the composite electrode offers numerous transportation channels for transfer of electrolyte and dissipation of the gaseous products. Moreover, the formation of a carbon layer during the synthesis of the composite improves the stability of the catalyst by preventing the agglomeration and dissolution of nanoparticles. Consequently, Ni3Fe nanoparticles with bicontinuous structure displayed enhanced catalytic activity for OER and required low overpotential only 248 mV to achieve a current density of 10 mA cm−2. Excellent activity and long-term durability of theses Ni3Fe nanoparticles make them an ideal substitute for the noble metal catalyst. We believe this work can provide an easy way for the synthesis of highly porous nanoparticles.

Three-dimensional graphene oxide-coated polyurethane foams beneficial to myogenesis

The development of three dimensional (3D) scaffolds for promoting and stimulating cell growth is one of the greatest concerns in biomedical and tissue engineering. In the present study, novel biomimetic 3D scaffolds composed of polyurethane (PU) foam and graphene oxide (GO) nanosheets were designed, and their potential as 3D scaffolds for skeletal tissue regeneration was explored. The GO-coated PU foams (GO-PU foams) were characterized by scanning electron microscopy and Raman spectroscopy. It was revealed that the 3D GO-PU foams consisted of an interconnected foam-like network structure with an approximate 300 μm pore size, and the GO was uniformly distributed in the PU foams. On the other hand, the myogenic stimulatory effects of GO on skeletal myoblasts were also investigated. Moreover, the cellular behaviors of the skeletal myoblasts within the 3D GO-PU foams were evaluated by immunofluorescence analysis. Our findings showed that GO can significantly promote spontaneous myogenic differentiation without any myogenic factors, and the 3D GO-PU foams can provide a suitable 3D microenvironment for cell growth. Furthermore, the 3D GO-PU foams stimulated spontaneous myogenic differentiation via the myogenic stimulatory effects of GO. Therefore, this study suggests that the 3D GO-PU foams are beneficial to myogenesis, and can be used as biomimetic 3D scaffolds for skeletal tissue engineering.

Spectral Properties of Nonlinear Schrödinger Equation on a Ring

The stationary states of nonlinear Schr{\"o}dinger equation on a ring with a defect is numerically analyzed. Unconventional connection conditions are imposed on the point defect, and it is shown that the system displays energy level crossings and level shifts and associated quantum holonomies in the space of system parameters, just as in the corresponding linear system. In the space of nonlinearity parameter, on the other hand, the degeneracy occurs on a line, excluding the possibility of any anholonomies. In contrast to the linear case, existence of exotic phenomena such as disappearance of energy level and foam-like structure are confirmed.

Lightweight, free-standing 3D interconnected carbon nanotube foam as a flexible sulfur host for high performance lithium-sulfur battery cathodes

The still hindered practical application of lithium-sulfur (Li-S) batteries with a high theoretical energy density of 2.6 kWh kg−1 can only be feasible by a simple and scaling-up fabrication of highly stable sulfur-based cathodes. Herein, a free-standing, mechanically flexible, binder-free 3D interconnected carbon nanotube ‘foam’ (CNTF) is prepared by a single-step facile method and used as a sulfur host in Li-S batteries. For the first time, such a simple method has been adopted for the preparation of free-standing CNT scaffolds for use in Li-S cells, as our method is free from the widely reported solvent-based techniques such as vacuum infiltration of CNTs to obtain free-standing forms but requires further purification and/or drying. A high-areal sulfur loading of 7.1mgScm−2, accounting to a total electrode mass of 10.9mgelectrodecm−2, with yet high electrochemical sulfur utilization of 72% is achievable by the foam-like CNT structure. Reversible areal capacities of up to 9mAhcm−2 at extremely low electrode weight (800mAhgelectrode−1) and specific capacities up to 1378mAhgS−1 are demonstrated. The interconnected porous network acts as a reservoir for trapping soluble lithium polysulfide compounds and greatly improves the sulfur reutilization. The lightweight CNT scaffold further provides enduring electrical contact with the sulfur species, resulting in excellent cycling stability and a potentially high gravimetric energy density desirable for automobiles and aerospace applications. The CNTF/sulfur composite cathode exhibits better rate performance and cycling stability than most of the recently reported CNT-based cathode materials for Li-S batteries.

Facile synthesis of 3D foam-like CoNiO2 for high-performance sodium ion batteries

3D foam-like CoNiO2 on Cu foil was synthesized by a low-temperature hydrothermal method with subsequent annealing treatment. The structure and composition of the 3D foam-like CoNiO2 have been analyzed by field-emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). When employed as anode electrode for sodium ion batteries, the as-prepared CoNiO2 film electrode exhibited a high reversible capacity of 323.7mAhg−1 after 100 cycles at 0.1Ag−1. Moreover, the CoNiO2 film electrode delivered an excellent rate capability of 210.3mAhg−1 at 1.6Ag−1. It is believed that the remarkable electrochemical performance of the film electrode is attributed to the 3D foam-like structure and binder-free feature, which effectively improve the ionic and electron conductivity of the electrode.

Processability of pure Zn and pure Fe by SLM for biodegradable metallic implant manufacturing

PurposeThis paper aims to investigate the processability by selective laser melting (SLM) of materials of potential interest for innovative biodegradable implants, pure Fe and pure Zn. The processability of these materials is evaluated with a more established counterpart in permanent implants, stainless steel. In particular, the processing conditions were studied to reduce porosity due to incomplete fusion of the powder.Design/methodology/approachIn the first phase of the experiments, SLM of AISI 316L was studied through design of experiments method. The study was used to identify the significant parameters in the experimental range and estimate the fluence ranges for pure Fe and pure Zn using the lumped heat capacity model. In the second phase, SLM of pure Fe and pure Zn were studied using estimated fluence ranges. In the final phase, best conditions were characterized for mechanical properties.FindingsThe results showed that complete melting of AISI 316L and pure Fe could be readily achieved, whereas laser melting generated a foam-like porous structure in Zn samples. The mechanical properties of laser melt implant materials were compared to as-cast and rolled counterparts. Laser melted AISI 316L showed superior mechanical performance compared to as-cast and rolled material, whereas Fe showed mechanical performance similar to rolled mild steel. Despite 12 per cent apparent porosity, laser melted Zn exhibited superior mechanical properties compared to as-cast and wrought material because of reduced grain size.Originality/valueThe paper provides key processing knowledge on the SLM processability of new biodegradable metals, namely, pure Fe, which has been studied sparingly, and pure Zn, on which no previous work is available. The results prefigure the production of new biodegradable metallic implants with superior mechanical properties compared to their polymeric counterparts and with improved degradation rates compared to magnesium alloys, the reference material for biodegradable metals.

Compressive failure mechanism and buckling analysis of the graded hierarchical bamboo structure

Bamboo is a unique unidirectional biocomposite, which consists of vascular bundles (VBs) as the reinforcement and parenchyma cells (PCs) as the matrix. The non-uniform distribution of VBs embedded in the matrix makes bamboo a functionally graded material. In order to investigate the compressive behavior of bamboo as a function of its components, compression tests were performed on specific bamboo samples with different VB volume fraction (V vb), collected from different positions in the culm wall. The results show that both compressive strength and modulus increased linearly with V vb, while the plastic deformation of samples in the compression decreased with increasing V vb. This indicates that VBs dominate the compressive strength and modulus of bamboo, while the ductile performance of the bamboo is determined by the foam-like PCs. Scanning electron microscope observation indicated that VBs buckling were the main cause of failure. The Euler theory was applied to investigate the buckling behavior of bamboo blocks, showing that theoretical buckling strength when only considering the effect of VBs was much lower than with the test results, with the theoretical buckling strength being closer to test results when considering both the effect of VBs and PCs. It is therefore necessary to consider the contribution of PCs to resist buckling in bamboo, as their foam-like structure can effectively prevent the large-scale buckling of VBs.