Diffusion of protons and sodium ions in silicophosphate glasses: insight based on first-principles molecular dynamic simulations.

We propose a microscopic diffusion mechanism of protons and Na+ ions in phosphate glasses using first-principles molecular dynamic simulations. Protons hop and are chemisorbed onto non-bridging oxygen (NBO) of nearby PO4 tetrahedra through hydrogen bonds. The subsequent behavior depends on the morphology of the PO4 tetrahedra (QnP values). When a proton is adsorbed onto the NBO of a Q3P unit, it is desorbed on a short time scale of within 10 fs and re-adsorbed onto the NBO that was previously adsorbed. However, when a proton is adsorbed onto the NBO of a Q2P unit, another proton coordinated before adsorption is desorbed in a chain, resulting in the diffusion of protons. When a Na+ ion is present in the vicinity, the adsorption of a proton onto a Q2P unit leads to a decrease in the electrostatic interaction between Na+ and O- ions and induces the diffusion of Na+ ions. We conclude that the difference in the morphology of PO4 tetrahedra greatly affects the diffusion of protons and Na+ ions.

Enhancing Wettability of Radio Frequency Magnetron-Sputtered Glass Films by Exploiting Structural Defects.

Silica-based films were prepared by radio-frequency magnetron sputtering to investigate the influence of the chemical compositions of the target glass on the structure and wettability of the sputtered films. The sputtered films were more hydrophilic than the untreated glasses. Oxygen defects formed in the silica units of the sputtered films and resulted in the formation of hydroxyl groups, regardless of the chemical composition of the glass. The three-phase contact lines were distorted by chemical heterogeneities on the surfaces of the sputtered films.

Construction of DNAzyme-Encapsulated Fibermats Using the Precursor Network Polymer of Poly(γ-glutamate) and 4-Glycidyloxypropyltrimethoxysilane.

Here, we developed functional nucleic acid (FNA)-encapsulated electrospun fibermats. To facilitate stable FNA encapsulation in the γ-PGA/GPTMS fibermats, we used the FNA as an FNA/streptavidin complex, and as a representative FNA, we selected a DNAzyme, the DNA/hemin complex, which is composed of G-quadraplex-forming single-stranded DNA and hemin and exhibits oxidation activity with the aid of a cocatalyst, H2O2. Scanning electron microscopy and Fourier-transform infrared spectroscopy measurements revealed that encapsulation of the DNA/hemin complex (∼1 wt % against the γ-PGA/GPTMS hybrid) in the nanofibers of the γ-PGA/GPTMS fibermats did not affect the structure of the original nanofibers. However, because a unique MW-dependent molecular permeability originated from the 3D network structure of the γ-PGA/GPTMS hybrid, low-MW substrates such as 4-aminoantipyrine, N-ethyl-N-(2-hydroxy-3-sulfopropyl)-3-methylaniline, and luminol were able to reach the encapsulated DNA/hemin complex by permeating to the inside of the nanofibers from an immersion buffer and then underwent catalytic oxidation. Conversely, nucleases, which are proteins featuring high MWs (>5 kDa), could not penetrate the γ-PGA/GPTMS nanofibers, and the encapsulated DNA/hemin complex was therefore effectively protected against nuclease digestion. Thus, encapsulating FNAs on the inside of the nanofibers of fibermats offers clear advantages for the practical application of FNAs in sensors and drugs, particularly for use in the in vivo circumstances.

Construction and Characterization of Protein-Encapsulated Electrospun Fibermats Prepared from a Silica/Poly(γ-glutamate) Hybrid.

Protein-encapsulated fibermats are an attractive platform for protein-based bioactive materials. However, the choice of methods is still limited and not applicable to a wide range of proteins. In this study, we studied new polymeric materials for constructing protein-encapsulated fibermats, in which protein molecules are encapsulated within the nanofibers of fibermats without causing deleterious changes to protein structure or function. We constructed a protein-encapsulated fibermat using the poly(γ-glutamate) (PGA)/(3-glycidyloxypropyl)-trimethoxysilane (GPTMS) hybrid as a precursor for electrospinning. Because the PGA/GPTMS hybrid is water-soluble, protein molecules can be added to the precursor in an aqueous solution, significantly enhancing protein stability. Polycondensation during electrospinning (in-flight polycondensation) makes the obtained fibermats water-insoluble, which stabilizes the fibermat structure such that it is resistant to degradation in aqueous buffer. The molecular structure of the PGA/GPTMS hybrid gives rise to unique molecular permeability, which alters the selectivity and specificity of biochemical reactions involving the encapsulated enzymes; lower molecular-weight (MW) substrates can permeate the nanofibers, promoting enzyme activity, but higher MW substrates such as inhibitor peptides cannot permeate the nanofibers, suppressing enzyme activity. We present an effective method of encapsulating bioactive molecules while maintaining their structure and function, increasing the versatility of electrospun fibermats for constructing various bioactive materials.

Informatics-Aided Density Functional Theory Study on the Li Ion Transport of Tavorite-Type LiMTO4F (M(3+)-T(5+), M(2+)-T(6+)).

The ongoing search for fast Li-ion conducting solid electrolytes has driven the deployment surge on density functional theory (DFT) computation and materials informatics for exploring novel chemistries before actual experimental testing. Existing structure prototypes can now be readily evaluated beforehand not only to map out trends on target properties or for candidate composition selection but also for gaining insights on structure-property relationships. Recently, the tavorite structure has been determined to be capable of a fast Li ion insertion rate for battery cathode applications. Taking this inspiration, we surveyed the LiMTO4F tavorite system (M(3+)-T(5+) and M(2+)-T(6+) pairs; M is nontransition metals) for solid electrolyte use, identifying promising compositions with enormously low Li migration energy (ME) and understanding how structure parameters affect or modulate ME. We employed a combination of DFT computation, variable interaction analysis, graph theory, and a neural network for building a crystal structure-based ME prediction model. Candidate compositions that were predicted include LiGaPO4F (0.25 eV), LiGdPO4F (0.30 eV), LiDyPO4F (0.30 eV), LiMgSO4F (0.21 eV), and LiMgSeO4F (0.11 eV). With chemical substitutions at M and T sites, competing effects among Li pathway bottleneck size, polyanion covalency, and local lattice distortion were determined to be crucial for controlling ME. A way to predict ME for multiple structure types within the neural network framework was also explored.

Poly(L-lactic acid)/vaterite composite coatings on metallic magnesium.

Poly(L-lactic acid)/vaterite composite materials were coated onto metallic magnesium substrates to control rapid degradation and to improve biocompatibility. Two types of composites were prepared by adding 30 and 60 wt% of vaterite to poly(L-lactic acid) (PLLA). The composite coating layer that contained 30 wt% vaterite in the PLLA matrix had almost no pores on the surface and suppressed the initial rapid degradation of the Mg substrate. After immersion in a culture medium for 7 days, pores of 0.5-1.0 µm in diameter formed on the surface. The composite coating layer that contained 60 wt% vaterite with pores of 1.0-2.0 µm in diameter on the surface did not suppress the degradation of the Mg substrate. During immersion, the pH of the media near the composite coating surfaces was maintained at 7.4-7.5 because of the degradation of PLLA and because the vaterite particles dissolved in the solution. Proliferation of murine osteoblast-like cells (MC3T3-E1) on the substrates was improved using composite coatings. Cells on the coating that contained 60 wt% vaterite had significantly higher proliferation than those on a bare Mg substrate. Our coating provides the optimum combination to suppress the initial Mg degradation and to promote cell growth on the coating surface by adjusting the vaterite content in the composite.

Setting time and formability of calcium phosphate cements prepared using modified dicalcium phosphate anhydrous powders.

Calcium phosphate cements (CPCs) were prepared using Ca4(PO4)2O (TeCP) and modified CaHPO4 (DCPA) to evaluate the effects of the powder properties for DCPA particles on the setting time and formability of the resulting CPCs. Two types of modified DCPA were prepared by milling commercially available DCPA with ethanol (to produce E-DCPA) or distilled water (to produce W-DCPA). The E-DCPA samples consisted of well-dispersed, fine primary particles, while the W-DCPA samples contained agglomerated particles, and had a smaller specific surface area. The mean particle size decreased with increased milling time in both cases. The raw CPC powders prepared using W-DCPA had a higher packing density than those prepared using E-DCPA, regardless of the mean particle size. The setting time of the CPC paste after mixing with distilled water decreased with decreases in the mean particle size and specific surface area, for both types of DCPA. The CPCs prepared using W-DCPA showed larger plasticity values compared with those prepared using E-DCPA, which contributed to the superior formability of the W-DCPA samples. The CPCs prepared using W-DCPA showed a short setting time and large plasticity values, despite the fact that only a small amount of liquid was used for the mixing of the raw CPC powders (a liquid-to-powder ratio of 0.25 g g(-1) was used). It is likely that the higher packing density of the raw CPC powders prepared using W-DCPA was responsible for the higher performance of the resulting CPCs.

Calculation of arrangement of oxygen ions and vacancies in double perovskite GdBaCo2O(5+δ) by first-principles DFT with Monte Carlo simulations.

The configurations of oxygen ions and vacancies at various oxygen stoichiometries and temperatures in double perovskite oxides (GdBaCo2O(5+δ), 0 ≤ δ ≤ 1) have been determined by density functional theory (DFT) combined with Monte Carlo (MC) simulations. The MC simulations confirmed the existence of a superstructure at δ = 0.5, showing alternating linear ordering of oxygen ions and vacancies along the b-axis in the GdO layer. This structure is identical to that reported experimentally. Increasing the temperature up to 1200 K induces a phase transition manifested in the breaking of the oxygen/vacancy arrangement at around δ = 0.5. In the high-temperature phase, vacancies are distributed in the GdO and CoO2 layers, whereas there are no vacancies in the BaO layer. In addition, the characteristic linear arrangement is partly preserved even in the disordered high-temperature phase. Consequently, oxygen ions can migrate between the GdO and CoO2 layers, as reported in previous classical molecular dynamics simulation studies.

Cotton wool-like poly(lactic acid)/vaterite composite scaffolds releasing soluble silica for bone tissue engineering.

Cotton wool-like poly(L-lactic acid) and siloxane-doped vaterite (SiV) composite scaffolds were prepared with a modified electrospinning system for bone tissue engineering applications. The effects of changing the SiV content in the materials from 10 to 30 wt% on elasticity and the ability to release calcium ions and soluble silica were evaluated. The elasticity of the cotton wool-like composites was almost the same as that of the PLLA from the results of compressibility and recovery tests. The materials released calcium ions for more than 56 days and soluble silica for 28-56 days in a tris buffer solution (pH 7.4). Mouse osteoblast-like cells (MC3T3-E1 cells) were cultured on/in the cotton wool-like materials or the fibremats out of the same composite materials as that used for the cotton wool-like materials. The cells penetrated into and proliferated inside the cotton wool-like materials, although they mainly adhered on the fibremat surface.

Siloxane-poly(lactic acid)-vaterite composites with 3D cotton-like structure.

Trace amounts of ionic calcium and silicon species have been reported to stimulate the proliferation, differentiation, and mineralization of bone-forming cells. Composite materials comprising siloxane-doped calcium carbonate (vaterite) particles and poly(L-lactic acid) have been developed [siloxane-poly(lactic acid)-vaterite hybrid-composite, SiPVH] so far; they were designed such that calcium and silicate ions are gradually released from SiPVH and they show the chronic effects of ions on cellular activities. In the present work, SiPVH with a 3D cotton-like structure was prepared by electrospinning to obtain the major advantages of excellent bioactivity and ease of handling for bone filling surgery. The diameter of the fibrous skeletons that form structure of the cotton-like SiPVH was controlled to ~10 µm to achieve cellular migration into the spaces between fibers. The resulting cotton-like SiPVH showed good flexibility. The fiber surface was coated rapidly with numerous particles of several hundred nanometers in size by alternate soaking in CaCl(2) and Na(2)HPO(4). The treated cotton-like material, which released calcium and silicate ions gradually, showed good cellular migration behavior into the 3D structure in cell culture tests using murine osteoblast-like MC3T3-E1 cells.

Structure and dissolution of silicophosphate glass.

P2O5-SiO2-Na2O-CaO glasses are promising therapeutic ion-releasing materials. Herein, we investigated the state of silicon (Si) in P2O5-SiO2-Na2O-CaO glass using a model with a composition of 55.0P2O5-21.3SiO2-23.7Na2O (mol%), incorporating a six-fold-coordinated silicon structure ([6]Si). The model was constructed using a classical molecular dynamics method and relaxed using the first-principles method. Further, we experimentally prepared glasses, substituting Na2O for CaO, to investigate the dissolution of glass with varying [6]Si and PO4 tetrahedra (Q P n ) distributions (n = number of bridging oxygens (BOs) to neighboring tetrahedra). [6]Si in the glass model preferentially coordinated with Q P 3. When Si was surrounded by phosphate groups, phosphorus (P) induced the formation of [6]Si by elongating the Si-O distance, and [6]Si acted like a glass network former (NWF). Na+ coordinated with [6]Si-O-P bonds via electrostatic interactions with BO. 31P and 29Si magic-angle-spinning-nuclear-magnetic-resonance spectra of three experimental glass samples with the compositions of 55.0P2O5-21.3SiO2-xCaO-(23.7 - x)Na2O (mol%, x = 0, 12.4, and 23.7) showed that Q P 3 and [6]Si increased with increasing Na2O. When each glass powder was immersed in a tris-HCl buffer solution at 37 °C, the dissolution of NWF ions and network modifier (NWM) ions increased almost monotonically with time for all samples, indicating that the solubility of the samples was suppressed by the coexistence of CaO and Na2O, attributed to the delocalization of the electron distribution of P in the [6]Si-coordinated Q P 3 units compared to that in the P- or [4]Si-coordinated Q P 3 units, which reduces hydrolysis.

Core-shell fibremats comprising a poly(AM/DAAM)/ADH nanofibre core and nylon6 shell layer are an attractive immobilization platform for constructing immobilised enzymes.

Core-shell fibremats, comprising poly(acrylamide)-co-poly(diacetone-acrylamide)/adipic dihydrazide [poly(AM/DAAM)/ADH] core-nanofibres and hydrophobic polymer shell layers, are a new class of platforms for constructing various immobilised enzymes. In this study, to elucidate the impacts of the shell-layer material on fibremat properties and enzymatic activities, we synthesised core-shell fibremats with shell layers comprising nylon6 or acetyl cellulose (AcCel) instead of poly(ε-caprolactone) (PCL), as in our previous study. Transmission and scanning electron microscopy images revealed that the lactase-encapsulated poly(AM/DAAM)/ADH-nylon6 and -AcCel fibremats were both constructed like the poly(AM/DAAM)/ADH-PCL one. Leakage measurements of the beforehand loaded molecules inside the core-nanofibres revealed that both fibremats exhibited efficient permeability for low-molecular-weight molecules and stable retention of enzyme molecules inside the core-nanofibres. Meanwhile, the fibremats' mechanical properties considerably depended on the choice of shell-layer material. The thermal analyses of the lactase-encapsulated fibremats revealed residual water inside the core nanofibres. The core-shell fibremats fabricated with a nylon6 or PCL shell exhibited excellent enzymatic activities (102 and 114%, respectively, compared to that of free lactase), superior to that of the same amount of free enzyme in a buffer. Furthermore, both core-shell fibremats retained over 95% of their initial enzymatic activities, even after they were re-used 10 times.

Silver-doped calcium silicate sol-gel glasses with a cotton-wool-like structure for wound healing.

Skin has excellent capacity to regenerate, however, in the event of a large injury or burn skin grafts are required to aid wound healing. The regenerative capacity further declines with increasing age and can be further exacerbated with bacterial infection leading to a chronic wound. Engineered skin substitutes can be used to provide a temporary template for the damaged tissue, to prevent/combat bacterial infection and promote healing. In this study, the sol-gel process and electrospinning were combined to fabricate 3D cotton-wool-like sol-gel bioactive glass fibers that mimic the fibrous architecture of skin extracellular matrix (ECM) and deliver metal ions for antibacterial (silver) and therapeutic (calcium and silica species) actions for successful healing of wounds. This study investigated the effects of synthesis and process parameters, in particular sintering temperature on the fiber morphology, the incorporation and distribution of silver and the degradation rate of fibers. Silver nitrate was found to decompose into silver nanoparticles within the glass fibers upon calcination. Furthermore, with increasing calcination temperature the nanoparticles increased in size from 3 nm at 600 °C to ~25 nm at 800 °C. The antibacterial ability of the Ag-doped glass fibers decreased as a function of the glass calcination temperature. The degradation products from the Ag-doped 3D non-woven sol-gel glass fibers were also found to promote fibroblast proliferation thus demonstrating their potential for use in skin regeneration.

Development of orthophosphosilicate glass/poly(lactic acid) composite anisotropic scaffolds for simultaneous reconstruction of bone quality and quantity.

Reconstruction of organ-specific architecture is necessary to recover the original organ function. The anisotropic structure of bone tissue is strongly related to the collagen fibril alignment and bone apatite crystal direction. Bone regeneration indicates following two main process; first, restoration of bone mineral density (BMD; bone quantity), and second, restoring bone apatite c-axis orientation (bone quality). In addition to BMD, bone quality is the most important factor among bone mechanical properties. Recovery of the original bone function requires development of novel scaffolds with simultaneous reconstruction of bone quality and quantity. Herein, novel orthophosphosilicate glass (PSG)/poly(lactic acid) composite anisotropic scaffolds were developed to control cell alignment and enhance bone formation, which are important for the simultaneous reconstruction of bone quality and quantity. The strategy to control cell alignment and bone formation involved designing anisotropic scaffolds in combination with the release of therapeutic ions by PSGs. The morphology of fibrous scaffolds containing PSGs was quantitatively designed using electrospinning. This successfully modulated cell alignment and subsequent bone apatite c-axis orientation along the fiber-oriented direction. The released silicate and Mg2+ ions from PSGs in scaffolds improved cell adhesion, proliferation, and calcification. To best of our knowledge, this is the first report demonstrating that the anisotropic scaffolds containing bioactive glasses regenerate bone tissues with simultaneous reconstruction of bone quality and quantity via stimulating osteoblasts by inorganic ions and designing morphology of scaffolds.

Structures and Dissolution Behaviors of Quaternary CaO-SrO-P2O5-TiO2 Glasses.

Calcium phosphate glasses have a high potential for use as biomaterials because their composition is similar to that of the mineral phase of bone. Phosphate glasses can dissolve completely in aqueous solution and can contain various elements owing to their acidity. Thus, the glass can be a candidate for therapeutic ion carriers. Recently, we focused on the effect of strontium ions for bone formation, which exhibited dual effects of stimulating bone formation and inhibiting bone resorption. However, large amounts of strontium ions may induce a cytotoxic effect, and there is a need to control their releasing amount. This work reports fundamental data for designing quaternary CaO-SrO-P2O5-TiO2 glasses with pyro- and meta-phosphate compositions to control strontium ion-releasing behavior. The glasses were prepared by substituting CaO by SrO using the melt-quenching method. The SrO/CaO mixed composition exhibited a mixed cation effect on the glassification degree and ion-releasing behavior, which showed non-linear properties with mixed cation compositions of the glasses. Sr2+ ions have smaller field strength than Ca2+ ions, and the glass network structure may be weakened by the substitution of CaO by SrO. However, glassification degree and chemical durability of pyro- and meta-phosphate glasses increased with substituted all CaO by SrO. This is because titanium groups in the glasses are closely related to their glass network structure by SrO substitution. The P-O-Ti bonds in pyrophosphate glass series and TiO4 tetrahedra in metaphosphate glass series increased with substitution by SrO. The titanium groups in the glasses were crosslink and/or coordinate phosphate groups to improve glassification degree and chemical durability. Sr2+ ion releasing amount of pyrophosphate glasses with >83% SrO substitution was larger than 0.1 mM at day seven, an amount that reported enhanced bone formation by stimulation of osteogenic markers.

Exfoliation Resistance, Microstructure, and Oxide Formation Mechanisms of the White Oxide Layer on CP Ti and Ti-Nb-Ta-Zr Alloys.

We found that specific biomedical Ti and its alloys, such as CP Ti, Ti-29Nb-13Ta-4.6Zr, and Ti-36Nb-2Ta-3Zr-0.3O, form a bright white oxide layer after a particular oxidation heat treatment. In this paper, the interfacial microstructure of the oxide layer on Ti-29Nb-13Ta-4.6Zr and the exfoliation resistance of commercially pure (CP) Ti, Ti-29Nb-13Ta-4.6Zr, and Ti-36Nb-2Ta-3Zr-0.3O were investigated. The alloys investigated were oxidized at 1273 or 1323 K for 0.3-3.6 ks in an air furnace. The exfoliation stress of the oxide layer was high in Ti-29Nb-13Ta-4.6Zr and Ti-36Nb-2Ta-3Zr-0.3O, and the maximum exfoliation stress was as high as 70 MPa, which is almost the same as the stress exhibited by epoxy adhesives, whereas the exfoliation stress of the oxide layer on CP Ti was less than 7 MPa, regardless of duration time. The nanoindentation hardness and frictional coefficients of the oxide layer on Ti-29Nb-13Ta-4.6Zr suggested that the oxide layer was hard and robust enough for artificial tooth coating. The cross-sectional transmission electron microscopic observations of the microstructure of oxidized Ti-29Nb-13Ta-4.6Zr revealed that a continuous oxide layer formed on the surface of the alloys. The Au marker method revealed that both in- and out-diffusion occur during oxidation in Ti-29Nb-13Ta-4.6Zr and Ti-36Nb-2Ta-3Zr-0.3O, whereas only out-diffusion governs oxidation in CP Ti. The obtained results indicate that the high exfoliation resistance of the oxide layer on Ti-29Nb-13Ta-4.6Zr and Ti-36Nb-2Ta-3Zr-0.3O are attributed to their dense microstructures composing of fine particles, and a composition-graded interfacial microstructure. On the basis of the results of our microstructural observations, the oxide formation mechanism of the Ti-Nb-Ta-Zr alloy is discussed.

Unravelling the dissolution mechanism of polyphosphate glasses by 31P NMR spectroscopy: ligand competition and reactivity of intermediate complexes.

Phosphate glass dissolution can be tailored via compositional and subsequent structural changes, which is of interest for biomedical applications such as therapeutic ion delivery. Here, solid-state 31P nuclear magnetic resonance characterisation of 45P2O5-xCaO - (55 -x)Na2O glasses was correlated with dissolution studies using time-dependent liquid 31P NMR spectroscopy and quantitative chemical analysis. Glasses dissolved congruently in aqueous media, and the first dissolution stage was the hydration of phosphate chains. In deionised water and Tris buffer (pH0 7.4 or 7.9), trimetaphosphate rings and orthophosphates were the predominant species in solution, indicating relatively fast degradation. By contrast, long phosphate chains were identified in EDTA (pH0 10.0). Besides pH differences, coordination of phosphate species by metal cations appears to play a catalytic role in the hydrolysis mechanism via turning phosphorus atoms into suitable electrophiles for the subsequent nucleophilic attack by water. Hydrolysis rates were proportional to phosphate complex stability, with stronger complexes for chains than for rings. A competition between solvent and phosphate species for the metal ion occurred in the order EDTA > Tris > deionised water.

Regulating size of silver nanoparticles on calcium carbonate via ultrasonic spray for effective antibacterial efficacy and sustained release.

Calcium carbonate is used as bone-filling material due to its good biocompatibility, bioactivity, and bioabsorbability, but the prevalence of infectious complications associated with calcium carbonate has created a persisting challenge in the treatment of bone defect. Therefore, this greatly necessitate the need to endow calcium carbonate with antibacterial properties. In this study, calcium carbonate powders loaded with silver nanoparticles (Ag-CaCO3) were prepared in attempt to serve as a novel antibacterial inorganic filler material. This objective was achieved using ultrasonic spray-pyrolysis (USSP) route to produce Ag-CaCO3 with 1, 5 and 10 mol% silver. The size of silver nanoparticles on CaCO3 microspheres could be regulated by adjusting silver concentration to facilitate effective release of Ag+ ions. This was demonstrated in Ag-CaCO3 (1), where the lowest silver content at 1 mol% achieved the highest Ag+ ions release over 28 days. This in turn gave rise to effective antibacterial efficiency against Staphylococcus aureus and Escherichia coli. Furthermore, CaCO3 (1) could also support osteoblast-like cells (MG-63) at a cell viability of 80%. Overall, this work extends the capabilities in employing USSP to produce inorganic filler materials with sustained antibacterial properties, bringing one step closer to the development of antibacterial products.

Heat transfer properties of Morpho butterfly wings and the dependence of these properties on the wing surface structure.

The heat transfer properties of a material strongly rely on its surface structure. The wings of the Morpho butterfly have a unique surface structure with features of order and disorder. In this work, the surface temperature and radiative heat flux of Morpho butterfly wings with structural colour when a ceramic heater attached to the opposite surface of the wings was heated to 250 °C were evaluated in terms of their heat transfer properties. Morpho menelaus butterfly (MM) wings and Cithaerias (CE) wings with no periodic structure on their surface, were used as samples. The MM wings had higher surface temperature and radiative heat flux than the CE wings, which is the first report of heat transfer properties of the wings. The surface structure of the MM wings was changed by heat treatment in order to investigate the effect of the surface structural change on their heat transfer properties. The treatment changed the colour of the wings to red and brown, distorting the periodic structure. The radiative heat flux increased due to the change in the structure on their surface. XPS spectra revealed that the treatment leads to a slight change in the chemical structure of the wings. The spectral analyses results showed there was no obvious change in the mid-infrared absorbance. The heat radiative properties of the MM wings were strongly influenced by the surface structural changes due to the heat treatment.

Water wettability dependence on surface structure of a snail shell.

There are many reports on the special wettability of hierarchical surface structures in nature. Snail shells with three types of roughness of 10, 100, and 500 µm have a unique wetting behavior. In the present study, we investigate the influence of the surface structure on the water wettability using snail shells with different surface roughness. The wettability of a water droplet on the samples was evaluated. The three types of roughness on the surface structure of snail shell had higher water droplet spreading properties than the two types of roughness 500 µm and, 10 or 100 µm. Surface structures of snail shells with different surface roughness were simulated using epoxy resins to clarify the mechanism for the dynamics wetting behavior. The contact angle with a hydrophobic nature, of the epoxy resin with the three types of roughness decreased with increasing time, indicating a hydrophilic nature. The base diameter of the epoxy resins with the three types of roughness increased with increasing time. This was larger than that for a flat epoxy resin with hydrophilicity. Other epoxy resins with shell texture containing 100 and 500 or 10 and 500 µm roughness showed almost no change in the contact angle and diameter of the droplet base. The three types of roughness on the sample surface contributed to development of the water droplet spreading. The 10 µm roughness of the sample surface influenced the dynamic contact angles.