This paper presents a fiber Bragg grating (FBG)-instrumented prosthetic silicone liner that provides cushioning for the residual limb and can successfully measure interface pressures inside prosthetic sockets of lower-limb amputees in a simple and practical means of sensing. The liner is made of two silicone layers between which 12 FBG sensors were embedded at locations of clinical interest. The sensors were then calibrated using a custom calibration platform that mimics a real-life situation. Afterward, a custom gait simulating machine was built to test the liner performance during an amputee’s simulated gait. To validate the findings, the results were compared to those obtained by the commonly used F-socket mats. As the statistical findings reveal, both pressure mapping methods measured the interface pressure in a consistent way, with no significant difference (P-values ≥0.05). This pressure mapping technique in the form of a prosthetic liner will allow prosthetics professionals to quickly and accurately create an overall picture of the interface pressure distribution inside sockets in research and clinical settings, thereby improving the socket fit and amputee’s satisfaction.
Long-range surface plasmon waveguides, and their application to various transducer architectures for amplitude- or
phase-sensitive biosensing, are discussed. Straight and Y-junction waveguides are used for direct intensity-based
detection, whereas Bragg gratings and single-, dual- and triple-output Mach Zehnder interferometers are used for phasebased
detection. In either case, multiple-output biosensors which provide means for referencing are very useful to
eliminate common perturbations and drift. Application of the biosensors to disease detection in complex fluids is
discussed. Application to biomolecular interaction analysis and kinetics extraction is also discussed.
The motion behavior of mammalian adipose tissue derived stem cells (AT-SCs) on an integrated channel waveguide under the evanescent field illumination is demonstrated and analyzed. The AT-SCs, suspended to a concentration of 1 x 105 cells per ml, are deposited in a reservoir over a copper ion-exchanged channel waveguide. Light from a HeNe laser operating at 632.8nm was coupled into the waveguide, causing the cells under the illumination of evanescent field and moved in a skewed stochastic motion in accordance to the laser power. The trajectory angle of the motion of the cells towards the illuminated channel waveguide was investigated and analyzed to distinguish the factors that affect such behavior. The cells reach a position relative to the illuminated channel, which is dictated by the compounded effect of the convectional current and evanescent field. The observations deduced that motion due to the optical field exists and were more pronounced when considering the trajectory angle towards the output facet. However, the optical forces are not significantly large enough to counter the motion due to the convection current. The results are discussed in light of the potential application of optical channel waveguides for bioanalytical applications, namely in the identification, sorting and analysis of differently sized mammalian cells without recourse to fluorescence or antibody staining.
Linewidth optimization of a fiber grating Fabry–Perot (FGFP) laser is performed numerically. In addition to the external optical feedback (OFB), the effect of temperature, injection current, cavity volume, gain compression factor, and external cavity parameters [i.e., coupling coefficient (C o ) and external cavity length (L ext )] on linewidth characteristics are investigated. The effects of external OFB and temperature on linewidth characteristics are calculated according to their effect on threshold carrier density (N th ). The temperature dependence (TD) of linewidth characteristics is calculated according to the TD of laser parameters instead of the well-known Pankove relationship. Results show that the optimum external cavity length (L ext ) is 3.1 cm and the optimum range of operating temperature is within ±2°C from the fiber Bragg grating (FBG) reference temperature (T o ). In addition, the antireflection (AR) coating reflectivity value of 1×10 −2 is sufficient for the laser to operate at narrow linewidth and low fabrication complexity. The linewidth can be reduced either by increasing the laser injection current or the strength of external OFB level.
The surface plasmon resonance (SPR) is one of the most attractive and precise enabling mechanism for sensors in
biomedical applications. Conventional biological experiments are performed manually, time consuming intervention and
expensive interconnection techniques. This paper simulates three dimensional behavior of magnetic and electric fields of
light coupled into a SPR mode propagating along a thin gold layer surrounded by symmetric dielectric layers. This study
successfully illustrates the three-dimensional simulation of surface plasmon wave using finite element method in
COMSOL Multiphysics suit.
Thermoluminescence (TL) flat optical fibers (FF) have been proposed as radiation sensor in medical dosimetry for both diagnostic and radiotherapy applications. A flat optical fiber with nominal dimensions of (3.226 × 3.417 × 0.980) mm3 contains pure silica SiO2 was selected for this research. The FF was annealed at 400°C for 1 h before irradiated. Kinetic parameters and dosimetric glow curve of TL response were studied in FF with respect to electron irradiation of 6 MeV, 15 MeV and 21 MeV using linear accelerator (LINAC) in the dose range of 2.0-10.0 Gy. The TL response was read using a TLD reader Harshaw Model 3500. The Time-Temperature-Profile (TTP) of the reader used includes; initial preheat temperature of 80°C, maximum readout temperature is 400°C and the heating rate of 30°Cs-1. The proposed FF shows excellent linear radiation response behavior within the clinical relevant dose range for all of these energies, good reproducibility, independence of radiation energy, independence of dose rate and exhibits a very low thermal fading. From these results, the proposed FF can be used as radiation dosimeter and favorably compares with the widely used of LiF:MgTi dosimeter in medical radiotherapy application.
Integrated optical devices offer dense, multifunctional capability in a single robust package but are rarely considered
compatible with the fields of remote or distributed sensing or compete in the long-haul with conventional 'one-dimensional'
fibers. Here we aim to change that by introducing a 'flat-fiber' process that combines the advantages of
of existing low-cost fiber drawing with the functionality of planar lightwave circuits in a novel hybrid format. Adapted
from MCVD fiber fabrication, our preforms are deposited and collapsed into a rectangular geometry before drawing,
resulting in extended lengths of mechanically flexible flat-fiber material with a photosensitive germanium-doped planar
core. Direct UV writing is then used to create arrays of channel waveguides within the core layer, using a 5μm focused
laser spot that literally 'draws' refractive index patterns into the flat fiber as it moves. Having recently demonstrated
simple building blocks for integrated optical circuits in millimeter-wide flat-fibers (including; channel waveguides,
power junctions and splitters, and planar Bragg gratings), our next step is to incorporate structured windows at strategic
points along the fiber to allow fluidic access to the evanescent field for local refractive-index-based chemical
measurements. By taking this approach, we hope to extend beyond the limitations of traditional planar and fiber
substrates, allowing exotic material compositions, device layouts, and local sensing functions to be distributed over
extended distances with no coupling or compatibility concerns in highly functional distributed lab-on-a-chip devices.
UV written planar waveguide sensors provide an integrated solution to refractive index sensors. The high sensitivity of the devices originate from their use of Bragg gratings which provide an accurate means of interrogating the local effective index. Conventionally the optical mode is made sensitive to an external refractive index by etching away the cladding and exposing it to an analyte. These devices have been used to sense liquid/solid phase changes and have displayed their potential for use as biological and chemical sensors. Recent results demonstrate sensitivities rivaling that of the highest specification Surface Plasmon Resonance (SPR) techniques. Here we introduce a new geometry which embraces the benefits of planar technology to realise new integrated devices. The geometry relies upon the use of a vertical trench or groove to produce an interface of optical quality which provides lateral access for an optical mode. The evanescent field interacts with the material within the groove and a Bragg grating in the region provides the means for interrogation. This reorientation of the sensor geometry provides additional flexibility to UV written devices, allowing several different sensors to be defined on the single substrate without multiple etching processes. These multiple sensors may offer complementary information such as the effective index as a function of penetration depth and interrogation wavelength for dispersion analysis. The paper also outlines the inherent feature benefits and fabrication advantages, including a reduction in return loss, spectral artefacts and stress induced birefringence.
Novel liquid crystal-based integrated optical devices with >140GHz electrical tuning are presented. Initial results with Bragg wavelength tuning covering five 25GHz WDM channel spacing have been achieved with 170V (peak-to-peak) sinusoidal voltages applied across electro-patterned ITO-covered glass electrodes placed 60μm apart. These prototype devices were fabricated using direct UV grating writing, with an evanescent field coupling into a liquid crystal overlay through an etched window. Two distinct threshold conditions are observed, manifesting only during the increase of supply voltage and forming a hysteretic tuning curve. The secondary threshold which takes place at higher voltages has never been reported before. We believe these threshold points are related to the formation and bleaching of disclination lines. Geometric and effective index consideration could not explain the similar tuning behaviour displayed by both TE and TM polarised light.
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