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1.
J Biophotonics ; 12(12): e201900218, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31452335

RESUMO

Modern document protection relies on the simultaneous combination of many optical features with micron and submicron structures, whose complexity is the main obstacle for unauthorized copying. In that sense, documents are best protected by the diffractive optical elements generated lithographically and mass-produced by embossing. The problem is that the resulting security elements are identical, facilitating mass-production of both original and counterfeited documents. Here, we prove that each butterfly wing-scale is structurally and optically unique and can be used as an inimitable optical memory tag and applied for document security. Wing-scales, exhibiting angular variability of their color, were laser-cut and bleached to imprint cryptographic information of an authorized issuer. The resulting optical memory tag is extremely durable, as verified by several century-old insect specimens still retaining their coloration. The described technique is simple, amenable to mass-production, low cost and easy to integrate within the existing security infrastructure.

2.
J Therm Biol ; 76: 126-138, 2018 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-30143287

RESUMO

The insect cuticle serves a multitude of purposes, including: mechanical and thermal protection, water-repelling, acoustic signal absorption and coloration. The influence of cuticular structures on infrared radiation exchange and thermal balance is still largely unexplored. Here we report on the micro- and nanostructured setae covering the elytra of the longicorn beetle Rosalia alpina (Linnaeus, 1758) (Coleoptera: Cerambycidae) that help the insect to survive in hot, summer environments. In the visible part of the spectrum, scale-like setae, covering the black patches of the elytra, efficiently absorb light due to the radiation trap effect. In the infrared part of the spectrum, setae of the whole elytra significantly contribute to the radiative heat exchange. From the biological point of view, insect elytra facilitate camouflage, enable rapid heating to the optimum body temperature and prevent overheating by emitting excess thermal energy.


Assuntos
Exoesqueleto/química , Regulação da Temperatura Corporal , Besouros/anatomia & histologia , Animais , Temperatura Alta , Luz , Modelos Biológicos , Termografia
3.
Biomed Mater ; 12(5): 055005, 2017 Sep 13.
Artigo em Inglês | MEDLINE | ID: mdl-28607223

RESUMO

Commercial collagen membranes are used in oral surgical procedures as scaffolds for bone deposition in guided bone regeneration. Here, we have enriched them with graphene oxide (GO) via a simple non-covalent functionalization, exploiting the capacity of oxygenated carbon functional moieties of GO to interact through hydrogen bonding with collagen. In the present paper, the GO-coated membranes have been characterized in terms of stability, nano-roughness, biocompatibility and induction of inflammatory response in human primary gingival fibroblast cells. The obtained coated membranes are demonstrated not to leak GO in the bulk solution, and to change some features of the membrane, such as stiffness and adhesion between the membrane and the atomic force microscopy (AFM) tip. Moreover, the presence of GO increases the roughness and the total surface exposed to the cells, as demonstrated by AFM analyses. The obtained material is biocompatible, and does not induce inflammation in the tested cells.


Assuntos
Colágeno/química , Fibroblastos/citologia , Gengiva/citologia , Grafite/química , Animais , Materiais Biocompatíveis/química , Adesão Celular , Proliferação de Células , Sobrevivência Celular , Humanos , Inflamação , Microscopia de Força Atômica , Nanoestruturas/química , Óxidos , Pós , Pele/química , Suínos , Tecidos Suporte
4.
Phys Rev E ; 95(3-1): 032405, 2017 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-28415223

RESUMO

Here we report how interference and scattering-enhanced absorption act together to produce the golden wing patches of the burnished brass moth. The key mechanism is scattering on rough internal surfaces of the wing scales, accompanied by a large increase of absorption in the UV-blue spectral range. Unscattered light interferes and efficiently reflects from the multilayer composed of the scales and the wing membranes. The resulting spectrum is remarkably similar to the spectrum of metallic gold. Subwavelength morphology and spectral and absorptive properties of the wings are described. Theories of subwavelength surface scattering and local intensity enhancement are used to quantitatively explain the observed reflectance spectrum.


Assuntos
Cor , Mariposas , Asas de Animais , Animais , Microscopia , Microscopia Eletrônica de Varredura , Modelos Biológicos , Mariposas/anatomia & histologia , Mariposas/efeitos da radiação , Espalhamento de Radiação , Asas de Animais/anatomia & histologia , Asas de Animais/efeitos da radiação
5.
J Biomed Opt ; 20(1): 016010, 2015 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-25574994

RESUMO

We performed a study of the nonlinear optical properties of chemically purified chitin and insect cuticle using two-photon excited autofluorescence (TPEF) and second-harmonic generation (SHG) microscopy. Excitation spectrum, fluorescence time, polarization sensitivity, and bleaching speed were measured. We have found that the maximum autofluorescence signal requires an excitation wavelength below 850 nm. At longer wavelengths, we were able to penetrate more than 150-um deep into the sample through the chitinous structures. The excitation power was kept below 10 mW (at the sample) in order to diminish bleaching. The SHG from the purified chitin was confirmed by spectral- and time-resolved measurements. Two cave-dwelling, depigmented, insect species were analyzed and three-dimensional images of the cuticular structures were obtained.


Assuntos
Quitina/química , Besouros/química , Microscopia de Fluorescência por Excitação Multifotônica/instrumentação , Microscopia de Fluorescência por Excitação Multifotônica/métodos , Animais , Artrópodes/química , Cavernas , Desenho de Equipamento , Imagem Tridimensional/métodos , Dinâmica não Linear
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