Biocompatibility and biosafety of butterfly wings for the clinical use of tissue-engineered nerve grafts

In a previous study, we used natural butterfly wings as a cell growth matrix for tissue engineering materials and found that the surface of different butterfly wings had different ultramicrostructures, which can affect the qualitative growth of cells and regulate cell growth, metabolism, and gene expression. However, the biocompatibility and biosafety of butterfly wings must be studied. In this study, we found that Sprague-Dawley rat dorsal root ganglion neurons could grow along the structural stripes of butterfly wings, and Schwann cells could normally attach to and proliferate on different species of butterfly wings. The biocompatibility and biosafety of butterfly wings were further examined through subcutaneous implantation in Sprague-Dawley rats, intraperitoneal injection in Institute of Cancer Research mice, intradermal injection in rabbits, and external application to guinea pigs. Our results showed that butterfly wings did not induce toxicity, and all examined animals exhibited normal behaviors and no symptoms, such as erythema or edema. These findings suggested that butterfly wings possess excellent biocompatibility and biosafety and can be used as a type of tissue engineering material. This study was approved by the Experimental Animal Ethics Committee of Jiangsu Province of China(approval No. 20190303-18) on March 3, 2019.

Numerical study on butterfly wings around inclusion based on damage evolution and semi-analytical method

Butterfly wings are closely related to the premature failure of rolling element bearings.In this study,butterfly formation is investigated using the developed semi-analytical three-dimensional(3D)contact model incorporating inclusion and material property degradation.The 3D elastic field introduced by inhomogeneous inclusion is solved by using numerical approaches,which include the equivalent inclusion method(EIM)and the conjugate gradient method(CGM).The accumulation of fatigue damage surrounding inclusions is described using continuum damage mechanics.The coupling between the development of the damaged zone and the stress field is considered.The effects of the inclusion properties on the contact status and butterfly formation are discussed in detail.The model provides a potential method for quantifying material defects and fatigue behavior in terms of the deterioration of material properties.

Preparation and Characterization of Hydrophobic Nano Silver Film on Butterfly Wings as Bio-template

Hydrophobic nano silver films were fabricated on butterfly wings as bio-template. The micrometric/nano structures and hydrophobicity of the surfaces were investigated with the help of scanning electron microscope（SEM） and video-based contact angle meter. The hydrophobic mechanism of silver film was analyzed with the aid of Cas- sie＇s formula. On the nano silver films of various thicknesses（5, 10, 20, 40, 60, 80, 100 nm）, all the contact an- gles（CAs） of water were bigger than 120°. When the silver film was 5 nm, the CAs of water on it on the wing surfa- ces of Mimathyma nycteis and Speyeria aglaja were 143.2° and 139.2°, respectively. Coated with the sliver film of the same thickness, butterfly wing surface exhibited the CA remarkably bigger than glass slide surface, exhibiting its high hydrophobicity. With the increase of silver film thickness on butterfly wing surface, the hydrophobicity kept de- creasing. The micrometric/nano hierarchical structures on butterfly wing surface result in the transition of metal silver from hydrophilicity to hydrophobicity.

Effects of Methanol on Wettability of the Non-Smooth Surface on Butterfly Wing

The contact angles of distilled water and methanol solution on the wings of butterflies were determined by a visual contact angle measuring system. The scale structures of the wings were observed using scanning electron microscopy, The influence of the scale micro- and ultra-structure on the wettability was investigated. Results show that the contact angle of distilled water on the wing surfaces varies from 134.0° to 159.2°. High hydrophobicity is found in six species with contact angles greater than 150°. The wing surfaces of some species are not only hydrophobic but also resist the wetting by methanol solution with 55% concentration. Only two species in Parnassius can not resist the wetting because the micro-structure （spindle-like shape） and ultra-structure （pinnule-like shape） of the wing scales are remarkably different from that of other species. The concentration of methanol solution for the occurrence of spreading/wetting on the wing surfaces of different species varies from 70% to 95%. After wetting by methanol solution for 10 min, the distilled water contact angle on the wing surface increases by 0.8°-2.1°, showing the promotion of capacity against wetting by distilled water.

Butterfly-wing hierarchical metallic glassy nanostructure for surface enhanced Raman scattering

The surface-enhanced Raman spectroscopy(SERS)is a technique for the detection of analytes on the surface with an ultrahigh sensitivity down to the atomic-scale,yet the fabrication of SERS materials such as nanoparticles or arrays of coinage metals often involve multiple complex steps with the high cost and pollution,largely limiting the application of SERS.Here,we report a complex hierarchical metallic glassy(MG)nanostructure by simply replicating the surface microstructure of butterfly wings through vapor deposition technique.The MG nanostructure displays an excellent SERS effect and moreover,a superhydrophobicity and self-cleaning behavior.The SERS effect of the MG nanostructure is attributed to the intrinsic nanoscale structural heterogeneities on the MG surface,which provides a large number of hotspots for the localized electromagnetic field enhancement affirmed by the finite-difference time-domain(FDTD)simulation.Our works show that the MG could be a new potential SERS material with low cost and good durability,well extending the functional application of this kind of material.

Excellent Color Sensitivity of Butterfly Wing Scales to Liquid Mediums

The ultrastructure characteristic and vivid colors of butterfly wing scales have attracted considerable attention recently. Surprisingly, these hyperfine structures also endow butterfly Trogonoptera brookiana wing scales the excellent color sensitive property to liquid mediums. In this work, the characteristic features of this excellent functional surface and the mechanism of its highly sensitive response characteristics were investigated. Firstly, the extraordinary and ordered nanostructures of this butterfly wing scales were characterized by a Field Emission Scanning Electron Microscope （FESEM）. Then, the ultra-depth three-dimensional （3D） microscope was used to observe the sensitive discoloration effect of the scales to liquid mediums. Afterwards, the highly spectral sensitive feature was identified by a mini spectrometer. In addition, the mechanism of this color sensitive effect of butterfly wing scales was revealed through modelling, calculation and simulation. It was found that this sensitivity is caused by the combined action of the microscale scales and the ultra-fine nanoscale structures in scale surface. On one hand, the arched and bended cover scales were stretched and superimposed by the filled ether solution. So, the color of the scales became reddish brown in an instant. On the other hand, the change of the fill mediums with different reflective index induced the modification of the surface interference, resulting in the peak shift of the reflectance spectrum. More importantly, the results of simulation and theoretical calculation were both in agreement with the experimental results. It illustrated that the butterfly TrogonOptera brookiana wings have repeatable sensitivity to liquid mediums, and obvious discoloration sensitive effect. This spectral sensitivity of butterfly wing scales has great prospect and meaning for the basic research and application of cheap, environmentally free and biodegradable sensitive element for water quality monitoring and analysis system.

Bioinspired C/TiO_2 photocatalyst for rhodamine B degradation under visible light irradiation

Papilio paris butterfly wings were replicated by a sol-gel method and a calcination process, which could take advantage of the spatial features of the wing to enhance their photocatalytic properties. Hierarchical structures of P. paris-carbon-TiO_2(PP-C-TiO_2) were confirmed by SEM observations. By applying the Brunauer-Emmett-Teller method, it was concluded that in the presence of wings the product shows higher surface area with respect to the pure TiO_2 made in the absence of the wings. The higher specific surface area is also beneficial for the improvement of photocatalytic property.Furthermore, the conduction and valence bands of the PPC-TiO_2 are more negative than the corresponding bands of pure TiO_2, allowing the electrons to migrate from the valence band to the conduction band upon absorbing visible light. That is, the presence of C originating from wings in the PP-C-TiO_2 could extend the photoresponsiveness to visible light. This strategy provides a simple method to fabricate a high-performance photocatalyst,which enables the simultaneous control of the morphology and carbon element doping.