PHOSFOS

PhosFOS is a research and technology development project co-funded by the European Commission.

Project Description

Figure 1: Flexible skin concept

Figure 2: Photograph of a real flexible skin with embedded sensors made at the University of Gent

The PHOSFOS (Photonic Skins For Optical Sensing) project is developing flexible and stretchable foils or skins that integrate optical sensing elements with optical and electrical devices as well as onboard signal processing and wireless communications, as seen in Figure 1. This flexible skins can be wrapped around, embedded in, attached and anchored to irregularly shaped and/or moving objects or bodies and will allow quasi-distributed sensing of mechanical quantities such as deformation, pressure, stress or strain. This approach potentially gives a significant advnatage over conventional sensing systems because of the portablility of the resulting systems and the extended measurement range.

The sensing technology is based around sensing elements called Fiber Bragg Gratings (FBGs) that are fabricated in standard single core silica fibers, highly birefringent Microstructured fibers (MSF) and Plastic optical fibers (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, fabricated within the programme. FBGS written in POF fibers will also be used since these fibers can be stretched up to 300% before breaking. This allows them to be used under conditions that would normally result in catastrophic failure of other types of strain sensors.

Once optimized the sensors are embedded into the sensing skin and on the interfaced to the peripheral optoelectronics and electronics. These skins are really flexible, see Figure 2.

The photonic skins developed in PHOSFOS have potential applications in continuously monitoring the integrity and the behavior of different kinds of structures in e.g. civil engineering (buildings, dams, bridges, roads, tunnels and mines), in aerospace (aircraft wings, helicopter blades) or in energy production (windmill blades) and therefore provide the necessary means for remote early failure, anomaly or danger warning. Applications in healthcare are also being investigated.

There is a movie describing the technology on YouTube.

Key results so far

Figure 3: Scattering of HeNe laser light from noise gratings recorded in PMMA using a 325 nm HeCd laser

File:Fabric with embedded POF sensors.jpg

Figure 4: Digital image correlation (DIC) image of the strain field in a fabric fitted with polymer optical fiber (POF) and silica gratings under a load of 20N, using dimethyl cyclosiloxane (DMC) and Araldite adhesive. FBG: Fiber Bragg grating. Si: Silicon. N: Newtons. MPa: Megapascals

A summary of the key developments can be found on the PhosFOS EU webpage [1] and include the demonstration of a fully flexible opto-electronic foil.

Figure 3 shows the scattering of HeNe laser light from noise gratings recorded in PMMA using a 325 nm HeCd laser.

One of the early results from the project was the successful demonstration of a repeatable method of joining the polymer fiber to standard silica fibre. This was a major development and allowed for the first time POF Bragg gratings to be used in real applications outside of the optics lab. One of the first uses for these sensors was in monitoring the strain of tapestries shown in Figure 4,. 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 the polymer devices are much more flexible they do not distort the material as much and therefore give a much most accurate measurement of the strain in flexible materials. Temperature and humidity sensing using a combined silica / POF fiber sensor has been demonstrated. Combined strain, temperature and bend sensing has also been shown. Using a fiber Bragg grating in an eccentric core polymer has been shown to yield a high sensitivity to bend.

Other recent progress includes the demonstration of birefringent photonic crystal fibers with zero polarimetric sensitivty to temperature, and a successful demonstration of transversal load sensing with fibre Bragg gratings in microstructured optic fibers.

The key areas where significant progress has been made are listed below :

1. Silica Microstructured fibers for temperature insensitive optical sensors

2. Embedded optoelectronic devices

3. Integrated sensors and optoelectronics

4. Polymer fiber Bragg gratings

5. Wavelength multiplexed polymer fibre Bragg gratings

6. Femtosecond fiber Bragg gratings

7. Polymers for flexible skinlike materials

8. Sensing system for Silica Microstructured fibers for pressure sensing

9. Sensing system for multimode Polymer fiber Bragg gratings

Consortium

• [2], Vrije_Universiteit_Brussel
• [3], Interuniversitair Micro-Electronica Centrum VZW
• [4], Universiteit_Gent
• [5], Politechnika Wroclawska
• [6], Maria Curie-Skłodowska University
• [7], Aston University
• [8], Fiber Optic Sensors and Systems BVBA
• [9], Cyprus University of Technology
• [10], Astasense Limited

External links

• http://www.phosfos.eu
• http://optics.org/cws/article/research/34671
• http://spie.org/x38859.xml?highlight=x2406&ArticleID=x38859
• http://spie.org/x39927.xml?ArticleID=x39927
• http://www.fos-s.be/projectsadv/be-en/1/detail/item/604/cat/19/
• http://rdmag.com/News/2008/10/Optical-foils-could--be-basis-for-artificial-skin/
• http://www.photonics.com/Article.aspx?AID=36120
• http://www.opticalfibersensors.org/news/be-en/143/detail/item/1305/
• http://www.ist-world.org/ProjectDetails.aspx?ProjectId=5959e74fdec54b57859fe30988c9add5&SourceDatabaseId=9900e74f1158484985c6bf0d2aa3cc2a

Open meetings

The 2nd "Benefits for Industry" Meeting of the EU FP7 Project PHOSFOS will take place on Sunday 22nd May 2011 in Munich (Germany).

The meeting is co-located with the Industry Meets Academia Workshop organized by SPIE SPIE as part of the Optical Metrology Conference. It will be followed by the World of Photonics Congress and the Laser World of Photonics Trade Fair in Munich, in the week from 23rd to 26th May 2011.

This Meeting is the second in its kind gathering all companies that have expressed their possible interest in the technology developed by the EU FP7 project PHOSFOS.

18 companies/institutes have registered for the Industrial User Club of PHOSFOS, new members are welcome.