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[[File:PhosFos flexible skin demo.jpg|thumbnail|right|400px|Figure 2: Photograph of a real flexible skin with embedded sensors made at the [[Ghent University]]]]
The PHOSFOS (Photonic Skins For Optical Sensing) project<ref>{{Cite web |url=http://www.phosfos.eu/eng/Phosfos/About-us/Project-Summary |title=Archived copy |access-date=2011-08-14 |archive-url=https://web.archive.org/web/20111127030416/http://www.phosfos.eu/eng/Phosfos/About-us/Project-Summary |archive-date=2011-11-27 |url-status=dead }}</ref> is developing flexible and stretchable foils or skins that integrate optical sensing elements with optical and electrical devices, such as onboard signal processing and wireless communications, as seen in Figure 1. These flexible skins can be wrapped around, embedded in, and anchored to irregularly shaped or moving objects and allow quasi-distributed sensing of mechanical quantities such as deformation, pressure, stress, and strain.<ref>{{Cite web|url=http://spie.org/x38859.xml?highlight=x2406&ArticleID=x38859|title = Artificial skin based on flexible optical tactile sensors}}</ref> This approach offers advantages over conventional sensing systems, such as increased portability and measurement range.
The sensing technology is based around sensing elements called [[Fiber Bragg Grating]]s (FBGs) that are fabricated in standard single core silica fibers, highly birefringent [[Microstructured fiber]]s (MSF) and [[Plastic optical fiber]]s (POF). The silica MSFs are designed to exhibit almost zero temperature sensitivity to cope with the traditional temperature cross-sensitivity issues of conventional fiber sensors. These specialty fibers are being modeled, designed, and fabricated within the programme. FBGs implemented in plastic optical fiber are also being studied because plastic fibers can be stretched up to 300% before breaking, permitting use under conditions that would result in catastrophic failure of other types of strain sensors.
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Figure 3 shows the [[scattering]] of HeNe [[laser]] light from noise gratings recorded in [[Poly(methyl methacrylate)|PMMA]] using a 325 nm HeCd laser.
One of the early results from the project was in developing a repeatable method for joining polymer fiber to standard silica fiber — a major development that enabled using POF Bragg gratings in applications outside an optics lab. One of the first uses for these sensors was in monitoring strain in tapestries<ref>http://eprints.soton.ac.uk/68650/01/137_Lennard.pdf</ref> shown in Figure 4,.<ref>{{Cite web|url=http://spie.org/x39927.xml?ArticleID=x39927|title = Polymer-fiber grating sensors}}</ref> In this case conventional electrical strain sensors and silica fiber sensors were shown to be strengthening the tapestries in areas where they were fixed. Because polymer fibre devices are much more flexible they did not distort the textiles as much, permitting more accurate measurement of strain.
Temperature and humidity sensing using a combined silica / POF fiber sensor has been demonstrated.<ref>Optical fibre temperature and humidity sensor, C. Zhang, W. Zhang, D.J. Webb, G.D. Peng, Electronics Letters, 46, 9, pp643-644, 2010, {{doi|10.1049/el.2010.0879}}</ref> Combined strain, temperature and bend sensing has also been shown.<ref>Bragg grating in polymer optical fibre for strain, bend and temperature sensing, X. Chen, C. Zhang, D.J Webb, G.-D. Peng , K. Kalli, Measurement Science and Technology, 2010</ref> Using a fiber Bragg grating in an eccentric core polymer has been shown to yield a high sensitivity to bend.<ref>Highly Sensitive Bend Sensor Based on Bragg Grating in Eccentric Core Polymer Fiber, X. Chen, C. Zhang, D.J. Webb, K. Kalli, G.-D. Peng, A. Argyros, IEEE Sensors Journal, 2010</ref>
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