1,721,125 research outputs found
Elastomeric-coated FBGs for point-of-care diagnostics
Full text linkThis study deploys the application of Fiber Bragg Gratings (FBGs) in physiological pressure monitoring by integrating an elastomeric, biocompatible coating ranging from 300-500μm, designed to improve sensor functionality for in-vivo pressure monitoring applications. FBGs are favored for their sensitivity, immunity to electromagnetic interference, and compact size, making them ideal for embedding within medical devices such as catheters and guidewires. However, their use has been limited by low inherent pressure sensitivity (3.14 pm/MPa) and the impracticality of thicker coatings described in previous studies. Our approach demonstrates that this unique coating not only boosts the pressure sensitivity significantly—surpassing 1.63 orders of magnitude (43.10 times)—but also enhances the signal-to-noise ratio of the optical signal. These advancements enable potential applications in high-resolution manometry, gastrointestinal pressure monitoring, intracranial and intracoronary blood pressure measurements, marking a significant step forward in medical diagnostics and monitoring
Photonic crystal X-shaped waves
No full textWe study out-of-plane three-dimensional wave localization in two-dimensional photonic crystals (PCs) and predict the existence of two types of stationary X-shaped waves at frequencies corresponding to either a local top point of a band, where the effective in-plane diffraction turns out to be negative, or at band saddle points. In the former case the X wave is directed along the invariance direction of the PC, whereas in the latter case it lies in the PC plane and directed along one of the principal directions of the diffraction tensor. Numerical results of localized waves for a PC with a square lattice, obtained in the spectral domain by superposition of isofrequency Bloch modes, are presented and confirm the analytical predictions based on an effective mass approach
Optical fiber pressure sensing for biomedical applications using frequency selective technique
No full textState-of-the-art optical fiber pressure sensors use displacement diaphragms and mechanical transducers to enhance pressure sensitivity, however, due to their bulkiness and large size they can’t be easily integrated inside pressure guide wire for intravital monitoring. Fiber Bragg Gratings (FBGs) due to their inherent advantages can be designed in a way that is suitable for monitoring Intracranial Pressure (ICP) and Instantaneous Wave-Free Ratio (iFR) pressure indices. The main disadvantage of FBG is that it has a low-pressure sensitivity of 3.04pm/MPa, which is insufficient for these applications and is made worse by the cross-sensitivity caused by temperature. We hereby present a two-pronged strategy to tackle this issue. The first step in improving sensitivity is to modify FBGs, and the second is to use signal processing methods to recover minor wavelength shifts. A frequency-selective detection technique can be used to measure sub-pm wavelength shifts for small modulated pressure signals. This technique was used to establish a test bench for measuring the pressure sensitivity of standard acrylate and polyimide coated FBGs as well as to confirm a linear relationship between the pressure range of interest and Bragg wavelength shift
Modified optical fiber sensors for intravital monitoring
No full textSensing using optical fibers is quite an established technology and is increasingly used in the field of bio-medical sensing applications owing to its small size, light weight, immunity towards electromagnetic interference, biocompatibility, sensitivity, and the ease with which it can be integrated with standard catheters leading to a designated point of inspection. Fiber Bragg gratings (FBGs), due to their ease of multiplexing, inherent sensitivity towards strain, and thereby pressure, can be suitably designed to make a novel pressure sensor for diagnosing and monitoring angiogenesis in brain tumors and for assessing vascular lesions inside coronary arteries. However, standard FBGs have a poor pressure sensitivity of 4pm/MPa (0.5fm/mmHg), which is insufficient to detect a few mmHg blood pressure changes. By utilizing the mechanical properties of modified FBGs with an elastomeric material coating, it is possible to improve the transduction mechanism of effectively translating pressure to strain and increase the resolution and sensitivity by two orders of magnitude (53.4 times) compared to standard FBGs. These modified FBGs could then be used to monitor respective pressure indices, i.e., Intracranial Pressure (ICP) and Instantaneous wave-free Ratio (iFR), by integrating them with catheters or endoscopes and using appropriate signal-processing algorithms. Moreover, a simulation of the modification of the blood vessel flow with respect to the secondary vessel formation is done to study the impact of different blood vessel formations during angiogenesis on pressure, thereby co-relating flow patterns to angiogenesis
Integrated devices in ferroelectrics for optical modulations and sensing
No full textWe will review the current status of domain inverted lithium niobate acousto- and electro-optic devices and show how the introduction of domain micro-engineering techniques can have a strong impact on modulators' performance enabling for a new class of integrated devices. We will also present potential applications of the proposed devices in increasingly important areas, such as advanced optical communication modulation formats, reconfigurable networks and sensors
Polymer-Based Optical Guided-Wave Biomedical Sensing: From Principles to Applications
Full text linkPolymer-based optical sensors represent a transformative advancement in biomedical diagnostics and monitoring due to their unique properties of flexibility, biocompatibility, and selective responsiveness. This review provides a comprehensive overview of polymer-based optical sensors, covering the fundamental operational principles, key insights of various polymer-based optical sensors, and the considerable impact of polymer integration on their functional capabilities. Primary attention is given to all-polymer optical fibers and polymer-coated optical fibers, emphasizing their significant role in enabling biomedical sensing applications. Unlike existing reviews focused on specific polymer types and optical sensor methods for biomedical use, this review highlights the substantial impact of polymers as functional materials and transducers in enhancing the performance and applicability of various biomedical optical sensing technologies. Various sensor configurations based on waveguides, luminescence, surface plasmon resonance, and diverse types of polymer optical fibers have been discussed, along with pertinent examples, in biomedical applications. This review highlights the use of biocompatible, hydrophilic, stimuli-responsive polymers and other such functional polymers that impart selectivity, sensitivity, and stability, improving interactions with biological parameters. Various fabrication techniques for polymer coatings are also explored, highlighting their advantages and disadvantages. Special emphasis is given to polymer-coated optical fiber sensors for biomedical catheters and guidewires. By synthesizing the latest research, this review aims to provide insights into polymer-based optical sensors current capabilities and future potential in improving diagnostic and therapeutic outcomes in the biomedical field
Room temperature direct bonding of LiNbO3 crystal layers and its application to high-voltage optical sensing
No full textLiNbO3 is a crystal widely used in photonics and acoustics, for example in electro-optic modulation, nonlinear optical frequency conversion, electric field sensing and surface acoustic wave filtering. It often needs to be combined with other materials and used in thin layers to achieve the adequate device performance. In this paper, we investigate direct bonding of LiNbO 3 crystals with other dielectric materials, such as Si and fused silica (SiO2), and we show that specific surface chemical cleaning, together with Ar or O2 plasma activation, can be used to increase the surface free energy and achieve effective bonding at room temperature. The resulting hybrid material bonding is very strong, making the dicing and grinding of LiNbO3 layers as thin as 15 νm possible. To demonstrate the application potentials of the proposed bonding technique, we have fabricated and characterized a high-voltage field sensor with high sensitivity in a domain inverted and bonded LiNbO3 waveguide substrate
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