PRESENTED BYDEBASISH MAHATA

ROLL NO: JFT-15email id:- debu.ijt@gmail.com

D.J.F.T, UNIVERSITY OF CALCUTTA

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INTRODUCTIONConsumer demand of unique appearance, increasedperformance and multifunctionality of the woven items,smart textiles became an active area of current research.Various applications of smart textiles include interactiveclothing for sports, hazardous occupations, and military,industrial textiles with integrated sensors or signage,fashion accessories and apparel with unique and variableappearance. Major advances in the textile capabilities canonly be achieved through further development of itsfundamental element - a fiber. In this work we discuss theprospectives of Photonic Band Gap (PBG) fibers inphotonic textiles.

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Total Internal Reflection (TIR) fibers modified to emitlight sideways have been used to produce emissivefashion items, as well as backlighting panels for medicaland industrial applications. To implement such emissivetextiles one typically uses common silica or plastic opticalfibers in which light extraction is achieved throughcorrugation of the fiber surface, or through fiber microbending. photonic textiles, a vast body of research hasbeen conducted to understand and to be able to design thelight scattering properties of synthetic non-optical fibers.

We start, by comparing the operational principles of theTIR fibers and PBG fibers for applications in opticaltextiles. We then highlight technical advantages offered bythe PBG fibers, compared to the TIR fibers, for the lightextraction from the optical fibers.

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Extraction of light from the optical fibers:‐

Light extraction from optical fibers. a) Microbending in TIR fibers. b) Surface corrugation in TIR fibers. c) Leaky modes in straight hollow core PBG fibers. d) Leaky modes in straight low refractive index solid core PBG fibers with scatterers at the fiber/air interface.

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UNDERSTANDING THE COLORS OF PBG FIBERS:‐

Colorful PBG Bragg fibers. a)When launching white light into the Braggfibers, after a few cm from the coupling end the fibers appear intenselycolored. Color of an individual fiber is defined by the spectral position of thefiber reflector band gap. b) Under ambient illumination, semi‐transparentBragg fibers appear colored again. Fiber color in reflection of the ambientlight can be different from the color due to emission of guided light.

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Color‐changing textiles under the variable ambient illumination:‐

a) Schematic of a color changing fiber. Color of a PBG fiber can be varied by mixing theemitted guided color with the reflected color from ambient illumination.b) Experimental demonstration of color mixing. c) A collection of lit fibers under strongambient illumination. Both the emitted guided colors (especially visible at the fiberperipheries) and the reflected colors (especially visible along the fiber center lines) arevisible. 6

Color‐on‐demand textiles using RGB yarns:‐

a) RGB yarn in the form of a braid of three fibers of R, G and B colors. b) Schematic of a color‐on‐demand textile setup.

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Experimental realization of the PBG fiber‐based textiles:‐

PBG Bragg fiber-based textile with a white silk matrix. When externallyilluminated the textile appears highly reflective showing stripes of differentcolors. When looked closely, the colored stripes are made of fibers of similardiameters; supporting silk ground cloth is visible through the transparent coloredfibers.

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Optical response of plastic PBG fibers to mechanical stretching:‐

PBG fiber textile and light coupling setup. a) Lit textile under the normal ambient illumination in the laboratory. b) Lit textile in the dark.The change in the fiber transmitted and reflected colors. One would expectthatunder mechanical strain, fiber dimensions would vary, thus having an impacton both the fiber appearance and transmission spectrum

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COLOUR CHANGING APPLICATIONS IN TEXTILE CHEMISTRY

Fiber's and coatings with unique optical, magnetic and electricalproperties are being widely researched for both military andcommercial applications. New materials are being developed inthis research effort, with unique tunable coloration propertiesacross the visible spectrum as well as spanning the infrared andultraviolet region of the electromagnetic spectrum. Thesedynamic color-responsive ‘camouflage’ fibre systems will havewide application to a variety of new textile products.

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Methods for production of camouflage textiles

A. pH changesB. Oxidation state changesC. Bond breaking/makingD. MechanochromismE. Electric or magnetic field effects

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Chromic materials:• Photochromic: external stimuli energy is light.• Thermochromic: external stimuli energy is heat.• Electrochromic: external stimuli energy is electricity.• Piezorochromic: external stimuli energy is pressure.• Solvatochromic: external stimuli energy is liquid.• Carsolchromic: external stimuli energy is electronbeam.

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CONCLUSION:‐We have presented an implementation of a photonic textilebased on plastic Photonic Band gap Bragg fibers for potentialapplications in smart cloths, signage and art. It was establishedthat under ambient illumination Bragg fibers appear coloreddue to optical interference in their microstructure. Compared toother existing PBG fibers, all-plastic Bragg fibers currentlyoffer the most economical solution required by the textileapplications.

The creation of fi eld-responsive fi bras, camouflage fi bras, isa multi-disciplinary endeavour. In addition to chromophores,polymeric materials may be able to generate a uniform, stablefi eld for excitation of the color change processes.

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THANK YOU

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