Measuring bite force gives important information about the performance of the jaw muscles. Enhancement of bite force measurements, particularly 2D force mapping, can be achieved through the application of advanced distributed fiber optics sensing techniques, which present the capability to acquire high resolution measurements. Optical Backscatter Reflectometry (OBR), based on the principles of Optical Frequency Domain Reflectometry (OFDR), is the key to achieve spatially distributed measurements and transform a single-mode fiber (SMF) into a cost-effective minimally invasive sensor. The OBR interrogator, manufactured by LUNA, catches the light backscattered by each section of the fiber and detects the spectral variation induced by the stain and pressure application. We have developed two methods to construct a two-dimensional map of the applied bite force. In the first a SMF has been bent into four lines and embedded into a silicone mouthguard. In the second approach we used massive Scattering‑Level Multiplexing (SLMux), which exploits fibers with different scattering levels: a standard low scattering SMF to enable the multiplexing, and a MgO‑nanoparticles doped fibers with a 40 dB higher scattering for sensing purposes. The setup with eight multiplexed fibers allows to obtain bite force mapping for each side of the jaw by embedding four fibers for left and right sides. The pressure sensitivity coefficient of the maps has been effectively calculated. The setup has been validated for 2D force mapping over the silicone mouthguard with millimeter resolution. The capability of optical fiber to be multiplexed and embedded in non-uniform geometries results in a high resolved and precise 2D bite force reconstruction.
Optical Backscatter Reflectometry (OBR) is capable of converting a simple and inexpensive single mode fiber (SMF) into an effective spatially distributed sensor of temperature and strain based on the concepts of Optical Frequency Domain Reflectometry (OFDR). A 2D sensing map of applied forces over a defined surface may be created by employing different spatial configurations of SMFs. This can be beneficial in biological applications such as measuring bite force. In this paper a 2D pressure sensing map based on distributed fiber optic sensing is provided. The two
dimensional technique is performed by bending the optical fiber along the surface to acquire ten lines embedded in silicone material, thereby generating a carpet of 2 by 6 cm. The highly resolved sensing map is created by spacing fiber lines 2 mm apart with a sensing range of 2 mm across the fiber. The embedded fiber detects distributed strain, which is subsequently transformed into a pressure map. The dependence of strain on the toughness of silicone material was observed. The map's pressure sensitivity coefficient has been effectively identified. The setup has been validated for surface measurement of wavelength shift values over 9 sensor carpet locations with a total of 310 sensing points. Since the sensor is embedded or attached to irregular forms and geometries, the distinctiveness of sensing surfaces allows for enhanced responsiveness to curvature due to its mechanical characteristics.
On the basis of Optical Frequency Domain Reflectometry (OFDR) principles, Optical Backscatter Reflectometry (OBR) is able to convert a simple and cheap single mode fiber (SMF) into an effective spatially distributed sensor of temperature and strain. By using different spatial configurations of SMFs, it can be obtained a 2D sensing map of applied forces over a delimited surface. This can be useful in biomedical applications such as force byte measurement. Here, a 2D pressure sensing map, based on distributed fiber optic sensing technique, is presented. The two-dimensional approach is achieved by bending the optical fiber along the surface to get ten lines embedded in silicone material, thus obtaining a carpet of 2 by 6 cm. The highly resolved sensing map is achieved by setting fiber lines 2 mm apart from each other with a sensing range of 2 mm over the fiber. The distributed strain, detected by the embedded fiber, is then converted into a pressure map. The pressure sensitivity coefficient of the map has been successfully characterized. The setup has been validated for surface measurement of wavelength shift values over 9 points on the sensing carpet with 310 total sensing points (10 fiber lines, each having 31 sensing points per 6 cm length). The peculiarity of sensing surfaces based on their mechanical properties gives an opportunity for improved response to curvature due to the embedding or attaching the sensor to irregular shapes and geometries.
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