2,749 research outputs found

    Revealing Invisible Photonic Inscriptions: Images from Strain.

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    Photonic structural materials have received intensive interest and have been strongly developed over the past few years for image displays, sensing, and anticounterfeit materials. Their "smartness" arises from their color responsivity to changes of environment, strain, or external fields. Here, we introduce a novel invisible photonic system that reveals encrypted images or characters by simply stretching, or immersing in solvents. This type of intriguing photonic material is composed of regularly arranged core-shell particles that are selectively cross-linked by UV irradiation, giving different strain response compared to un-cross-linked regions. The images reversibly appear and disappear when cycling the strain and releasing it. The unique advantages of this soft polymer opal system compared with other types of photonic gels are that it can be produced in roll to roll quantities, can be vigorously deformed to achieve strong color changes, and has no solvent evaporation issues because it is a photonic rubber system. We demonstrate potential applications together with a fabrication procedure which is straightforward and scalable, vital for user take-up. Our work deepens understanding of this rubbery photonic system based on core-shell nanospheres.We acknowledge financial support from EPSRC grant EP/G060649/1, EP/I012060/1, EP/J007552/1, ERC grant LINASS 320503, EMATTER 280078.This is the accepted manuscript. The final version is available at http://pubs.acs.org/doi/abs/10.1021/acsami.5b02768

    Exploiting pattern transformation to tune phononic band gaps in a two-dimensional granular crystal

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    The band structure of a two-dimensional granular crystal composed of silicone rubber and polytetrafluoroethylene (PTFE) cylinders is investigated numerically. This system was previously shown to undergo a pattern transformation with uniaxial compression by Göncü et al. [Soft Matter 7, 2321 (2011)]. The dispersion relations of the crystal are computed at different levels of deformation to demonstrate the tunability of the band structure, which is strongly affected by the pattern transformation that induces new band gaps. Replacement of PTFE particles with rubber ones reveals that the change of the band structure is essentially governed by pattern transformation rather than particles¿ mechanical properties

    Fabrication of Low Adhesion Films Through Pulsed Light Sintering

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    Pulsed photonic sintering/curing of materials has significant potential to change the way we process thin films. The pulsed light technology has tremendous benefits with processing time lying in the order of milliseconds. This process can be used to thermally process printed films and has huge energy saving potential when compared to conventional thermal processes. This research specifically aims at fabrication of low adhesion polymer film coatings, such as Teflon, using an energy efficient photonic sintering technique. Teflon, due to its non-stick properties, is widely used in printing processes, cooking accessories, antireflection windows and in several other applications. Sintering of Teflon through pulsed light technology has not been studied, hence this research has tremendous potential to revolutionize the way the Teflon films are processed. This research studies the conditions for sintering PTFE, PFA and FEP nanoparticle films on platinum-coated silicone rubber. Scanning electron microscopy was used to study the sintered samples to reveal the magnitude of particle consolidation on the samples. A Fluke Energy Meter was used to study the energy consumption for both photonic sintering and conventional oven sintering. The results from the studies show substantially energy savings for photonic sintering. The research discusses the conditions under which the best particle sintering was obtained for the PTFE and PFA
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