Vert | EPFL Graph Search

vignette|Les verts de la végétation. Le vert est un champ chromatique regroupant les couleurs situées sur le cercle chromatique entre le jaune et le bleu. Contrairement à d'autres couleurs, qui changent de nom quand elles sont lavées de blanc ou rabattues avec du noir, comme le rouge qui devient rose ou brun, le vert conserve son nom, vert pâle ou vert foncé, vert vif ou vert grisâtre. Le vert dû à la chlorophylle est la couleur de la plupart des feuillages de la végétation. Colorimétrie et perception des couleurs Selon la norme AFNOR X08-010 « Classification méthodique générale des couleurs » (annulée en 2014), les verts sont des couleurs dont la longueur d'onde dominante est comprise entre 490 et . Les longueurs d'onde les plus courtes correspondent à des verts tirant vers le bleu, comme le vert turquoise ; les plus longues correspondent à des verts tirant vers le jaune. Pour d'autres auteurs, le vert correspond à une longueur d'onde dominante entre 497 et ; selon Ch

Nature-inspired Circular-economy Recycling (NaCRe) for Proteins

Simone Giaveri

Since a few decades our planet has been loaded with billion tons of synthetic polymer-based materials, commonly named plastics. The large scale of plastic production, associated with its limited recyclability, are the driving force for the accumulation of such materials into the environment. Garbage patches, i.e. islands of plastics in the ocean, are striking evidences of this issue. A sustainable handling, that is production and disposal, of synthetic polymer-based materials is one of the greatest challenges that humanity has to face.Proteins and nucleic acids are natural polymers. Arguably, Nature produces an amount of such polymers that is higher with respect to man-made polymers. However, these materials do not accumulate into the environment, that is the approach used by Nature to handle these polymers is sustainable. The secret for its sustainaibility lies on the circularity in the materialsâ use. Indeed, proteins and nucleic acids are sequence-defined polymers that undergo depolymerization to monomers, and recycling into new materials by reassembling the so obtained monomers into arbitrarily different sequences. Organisms digest proteins into amino acids. These monomers are in turn polymerized to produce the protein of need, at the time of the protein synthesis.In this thesis we show that this process is achievable outside living organisms. Indeed, we depolymerized structurally different short peptides, and peptides mixtures into their constitutive amino acids, and recycled such monomers into biotechnologically relevant proteins (green, and red fluorescent proteins), by using an amino acid-free cell-free transcription-translation system. We further applied our methodology to recycle proteins with high relevance in materials engineering such as Î²-lactoglobulin films, used for water filtration, or silk fibroin solutions into green fluorescent protein. We were also successful in recycling mixtures composed of short peptides, and technologically relevant proteins into fluorescent proteins, as well as into bioactive enzymes (catechol 2,3-dioxygenase). Finally, we achieved multiple cycles of recycling (two cycles), and we demonstrated that the strategy can be expanded beyond the set of the twenty proteinogenic amino acids.Presented herein is a nature-inspired approach to recycling of soft materials, where unknown mixtures of polymers are recycled into the polymer of need, by the local community, at the time of recycling. The materials are costantly transformed into different ones, without any external feed, and there is no way to distinguish a new polymer from a recycled one. The strength of this method lies in its compatibility with the principles of circular economy.

EPFL2021

Up-scalable plasmonic and diffractive nanostructures

Fabian Michael Lütolf

Since most of the academic photonic and plasmonic nanostructures are based on slow and expensive electron beam lithography processes, there is a need for innovative alternatives suitable for industrial manufacturing. Large areas need to be patterned with a high throughput, which is for example achieved with roll-to-roll machines. Up-scalable designs of photonic and plasmonic nanostructures are therefore studied in this thesis. Typical industrial processes include embossing and evaporation, which are consequently used throughout the thesis. I propose oblique evaporation of high refractive index materials to render binary gratings highly efficient for first order transmission. Zinc sulfide coatings are employed to diffract close to 70% of unpolarized green light. Simulations further show that they can be encapsulated to protect them from environmental influences like humidity, wear or dust, while retaining their exceptional diffractive properties, which is very appealing for outdoor applications. I also show that thin metallic coatings can attain similar efficiencies for TE polarized light. The effect is asymmetric and shows a maximum at the Wood-Rayleigh anomaly, which results in orientation dependent coloration of the zero order as well as first order transmittances. A large part of the standard RGB gamut can be covered through proper adjustment of the grating parameters. Combination of zero order and first order effects allows creation of color appearances that switch when rotating or flipping the device. I finally present how floating images become apparent when a patterned light source like e.g. a mobile phone is used in conjunction with the metallized grating. Direct transfer of plasmonic technology from universities to industry is often not possible: in academia, metallic nanostructures often require a lateral resolution of a few nanometers, which is challenging to achieve in up-scalable processes. Thicknesses on the other hand can be controlled in this regime using evaporation techniques, which are hence powerful methods for high-throughput production. In this thesis, Fano-resonant, U-shaped nanowires are created with oblique metal deposition. In order to make them available for mass-production, aluminum is chosen as the plasmonic material. The surface integral equation method is used to investigate near-fields and charge distributions, which shed light onto the physics behind the present resonances. A surface plasmon polariton is found to couple to a localized plasmonic mode with a hexapolar charge distribution. It is finally shown that the Fano-resonance can be accurately tuned by adapting evaporation angle and metal thickness. These two parameters can easily be accessed and would allow for good control over the optical response even in an industrial environment. The applicability of the above insights is then demonstrated by creating a strain sensor. To that end, the process is transferred to a stretchable polymer and when elongating the structure perpendicular to the wires, the polymeric spacing between them is expanded. The sensitivity of the Fano-resonance to this change in inter-wire distance is investigated and a strong damping is observed. Through careful design, a clearly visible color switch from purple to green is achieved for elongations less than 20%. The sensor was deemed to be very durable, as no deterioration in the color or the spectral response was observed even after several strain cycles.

EPFL2015

Spectral cola or how to turn green laser light red

Csaba Forro, Thibaud Humair, Xavier François Mettan

A green laser pointer shone through a glass of cola will appear red when looking from above the glass. Lowering the laser so that it is deeper in the cola, the colour will vary from orange to deep red. Fluorescence and absorption spectra were recorded consistent with the reddening of the laser. The depth dependence of the colour of the immersed laser is attributed to a more significant absorption of the short wavelengths by the cola, making the laser look redder as it is lowered deeper into the cola. To confirm this hypothesis, we simulated the fluorescence spectrum we would get at various depths by applying the Lambert law on our measured fluorescence spectrum. These spectra were then converted into red, green and blue (RGB) values. These values were compared to those measured on images of the immersed laser beam at corresponding depths.

Iop Publishing Ltd2014