Smart Sensing Polymeric Foil with Integrated Optic Fiber Sensors Fabrication and characterization of a polymeric foil sensitive to strain. A. F. Silva, P. M. Mendes, J. H. Correia Department of Industrial Electronics University of Minho Guimaraes, Portugal asilva@dei.uminho.pt F. Goncalves R&D Department TMG Automotive Campelos, Guimaraes, Portugal filipe.goncalves@tmgautomotive.pt L. A. Ferreira, F. M Araujo INESC Porto Faculty of Science University of Porto Porto, Portugal L. A. Ferreira, F. M Araujo FiberSensing Maia, Portugal luis.ferreira@fibersensing.com francisco.araujo@fibersensing.com Abstract— A structural integrity monitoring system based on optic fiber sensors is an important development at the smart structures level. However, direct sensors incorporation, without a substrate structure, creates few difficulties in eventual sensor maintenance or replacement. This paper presents an approach to overcome this issue. The fabrication, using industrial fabrication processes, and characterization of a polymeric foil able to sense and gather sensitive information, and send it for remote analysis is explored. The described example uses Fiber Bragg Grating sensors embedded in laminated polymeric sheets commonly used in different industries, as automotive, aeronautic, civil, among others. The fabricated foil is capable of transferring the full deformation to the optical sensor. Tests indicate that the polymeric foil influence on the sensor performance may exist. However, the presented optical sensor incorporated in the polymeric foil is fully functional with high sensitivity, 0,6 picometer by microstrain, measuring deformation, up to 1,2 millimeter. Keywords- optical sensors; smart structures; fiber Bragg gratings, sensor integration I. INTRODUCTION Optical sensing technologies have several advantages that make them very attractive in a broad range of applications. Optical fiber sensors, in particular, provide low-cost solutions in the overall system, with immunity to electromagnetic interference, multiplexing capabilities and a high degree of miniaturization and integration. Nowadays, optical fiber sensors offer a high performance alternative, in comparison to standard technologies, in many different areas, either to measure physical parameters like strain, temperature or pressure, or to perform highly sensitive biochemical analysis [1, 2]. However, the incorporation of such sensors creates some difficulties in eventual sensor maintenance or replacement. Alternatively, it is proposed in this paper to incorporate optoelectronic instrumentation in standard polymeric foils that can be already found in different products, e.g., automotive and air craft floors and wall coverings. The advantages come from the easy applicability of foils in the monitored structure, allowing also the easy access for replacement. Moreover, integrated optical devices are now emerging as the next generation of sensing structures, where virtually any parameter can be determined with high accuracy in a highly miniaturized optoelectronic device [3]. Linking textiles or textiles-polymer-laminates with optical devices and electronics is becoming more realistic than ever. An emerging new field of research that combines the strengths and capabilities of electronics, optics and polymers like PolyVinyl Chloride (PVC) is opening new opportunities. Industries, like the automotive, aeronautics, civil and biomedical are looking for solutions to gather information from their systems status. Lower production costs, wider exploitation of integrated circuit technology and wider applicability of sensor networks allows the integration of microsensors in almost any structure, providing the desired system data. A. Fiber Bragg Grating Sensors Fiber Bragg Gratings (FBG) are periodic changes in the refraction index of the fiber core made by adequately exposing the fiber to intense UV light. The gratings produced typically have lengths of the order of 10 mm [4]. When an optical beam is injected into the fiber containing the grating, the wavelength spectrum corresponding to the grating pitch will be reflected, while the remaining wavelengths will pass through the grating undisturbed, as exemplified in Figure 1 [5, 6]. Since the grating period structure is sensitive to strain and temperature, these two parameters are measured by the analysis of the reflected light spectrum. This is typically done using a tunable laser containing a wavelength filter (such as a Fabry–Perot cavity) or a spectrometer [4].