This paper presents an enhanced concave tip optical fiber (CTOF) probe for dopamine (DA) detection based on localized surface plasmon resonance (LSPR) and DNA aptamers as sensing elements. The CTOF probe was fabricated using chemical etching and optimized for the confinement factor to improve the refractive index (RI) sensitivity by enhancing the LSPR field. The RI sensitivity of the LSPR-CTOF sensor, measured in the range of 1.3332-1.3604 RIU, was obtained at 1716 nm/RIU, demonstrating a 323.9% increase compared to the conventional flat tip fiber (FTF) structure. Fiber optic sensing probes were created by immobilizing the Au nanoparticles (AuNPs) and specific DNA aptamers on the tip of the fiber. The DA sensitivity of the sensor was obtained at 1.78 nm/log(M) across a wide concentration range of 100 fM-1mM. Additionally, the limit of detection and quantification were achieved at 2.5 fM and 16.3 fM, respectively. The selectivity of the sensor was evaluated using ascorbic acid and epinephrine. Moreover, repeatability and stability were studied in detail. These findings show that these Apta-biosensors based on LSPR are good candidates for in-vivo DA detection.

Alzheimer's disease (AD) presents an increasing global health challenge, highlighting the need for early and accessible diagnostic methods. This study introduces a highly sensitive optical fiber apta-biosensor based on localized surface plasmon resonance (LSPR) for the early detection of Amyloid beta (1-42) (A beta(42)), a crucial biomarker for AD. The RI sensitivity of the sensor was obtained at 716.53 nm/RIU which can be used as a good candidate for label-free biosensing. Upon A beta(42) binding, a distinct blue shift was observed, with a detection limit of 0.01 fM and a detection range from 50 fM to 5 mu M. The sensor's high sensitivity, real-time monitoring, and label-free operation highlight its potential as a cost-effective alternative for early AD diagnosis, paving the way for widespread clinical applications.

Plasmonic optical sensors are widely employed for various applications, including biomedical and chemical sensing. More accurate and precise detection can be achieved by ameliorating sensitivity and compensating for unwanted environmental interfering parameters, including temperature dependency. The present study demonstrates the effect of low annealing temperatures on localized surface plasmon resonance (LSPR) in flat tip fiber (FTF) sensors, which enhances the refractive index (RI) sensitivity and thermal compensation. The RI sensitivity of the sensor was measured in the range of 1.3332 RIU to 1.3604 RIU, and temperature sensitivity was measured in the range of 20 degrees C to 50 degrees C for annealed fiber optic probs at 100 degrees C, 200 degrees C, and 300 degrees C, and an unannealed prob. Temperature-induced morphological changes of the properties of NPs in FTF-LSPR can significantly increase the RI sensitivity by approximately 134.4 %, improve the figure of merit (FOM) by around 487.5 %, and decrease the limit of detection (LOD) by about 60.2 %. Also, temperature annealing leads to thermal compensation of the LSPR sensor, making these sensors particularly suitable for biosensing applications and label-free detection. Furthermore, annealing at 300 degrees C induced NP fusion, generating distinctive plasmonic characteristics by demonstrating transverse and longitudinal resonance modes, forming dual-dips spectral features with high potential applications in dual-sensing of RI and temperature for biosensing platforms.

The advent of optogenetic tools has revolutionized neuroscience research through its spatiotemporally precise activation of specific neurons by illuminating light on opsin-expressing neurons. A long-standing challenge of in vivo optogenetics remains in delivering light to multiple brain sites simultaneously and maintaining high spatial resolution. Optical fiber-based technologies have been proposed to address these challenges. This work presents the fabrication and characterization of an innovative angled optical fiber probe based on a double-sided angled tip (DSAT) structure. A custom griding setup was used for the reproducible fabrication of a smooth DSAT probe. The designed probe enables precise spatial control of light propagation in brain tissue in which DSAT at angled tip 55 degrees achieving a maximum lateral illumination position of +/- 420 mu m away from the optical axis and a peak irradiance of 478.5 mW/mm(2), using a 5 mW of 473 nm laser light. Also, the designed DAST probe was simulated based on ray tracing method and obtained the practical tip angle to evaluate the propagation of light rays emitted from the DSAT at various input optical angles ranging from 0 degrees to 12.5 degrees to predict their irradiance and positions in the modelled tissue. The results indicate the probe generates two elliptical rings each containing two spots with higher optical concentration. Consequently, this device provides four optical spots with irradiance peaks that enable simultaneous illumination of four different locations in the brain tissue. Obtained experiment results are in good agreement with simulation results which can be used for multipoint illumination of brain tissue in optogenetics applications.

Frazao This paper introduces an innovative two-core fiber (TCF) optic sensor employing a Mach-Zehnder interferometer (MZI) to monitor the optogenetic response of light-sensitive human dental pulp stem cells (hDPSCs). The in-fiber MZI, formed using a segment of TCF optic, detects refractive index (RI) changes in the surrounding medium. The sensor utilizes the evanescent wave of one core as the sensing arm, necessitating a thin cladding achieved through one-sided chemical etching. This design allows the sensor to detect subtle alterations in the RI of the environment by observing displacements in the interference spectrum. The optogenetic stimulation of light-sensitive cells induces variations in ion concentrations, leading to a corresponding change in refractive index. The fabricated sensor, with a peak sensitivity of 675.74 nm/RIU within the RI range of 1.39-1.43, can detect these changes. A computer simulation validated the sensitivity and optimized fabrication parameters, exhibiting satisfactory agreement with experimental results. Spectrum displacements were recorded for both light-sensitive hDPSCs and regular hDPSCs (as a control test). Results from the experiment, analyzed and compared using data analysis software, revealed that 473 nm blue light effectively stimulated light-sensitive hDPSCs. Notably, the proposed sensor, a novel structure, demonstrated its capability to detect RI changes in the cell medium during optogenetic applications.

The application of optical fibers in optogenetics is rapidly expanding due to their compactness, cost-effectiveness, sensitivity, and accuracy. This paper introduces a twin-core optical fiber (TCF) sensor employing a Mach-Zehnder interferometer (MZI) to monitor the optogenetic response of opsin-expressing human dental pulp stem cells (hDPSCs) based on refractive index (RI) measuring. In order to improve the RI sensitivity of the sensor, an in fiber Mach-Zeander modulator formed using TCF optics segments can detect changes in the RI in the surrounding medium, and in order to improve the RI sensitivity of the sensor, it is proposed to etch one side of the TCF cladding. The RI sensitivity of the sensor was obtained 233.62 nm/RIU in the range of 1.33-1.4 RIU and 870.01 nm/RIU in the range of 1.4-1.43 RIU, R2 = 0.99. simulation results show that in terms of sensor sensitivity and spectral response, there is a good agreement between the theoretical and experimental results, indicating that the TCF-MZI sensor can perform optical neural recording. In vitro experiments monitored wavelength changes in opsin-expressing and non-opsin-expressing in human dental pulp stem cells (hDPSCs) during optogenetic stimulation with 473 nm pulsed illumination. The results revealed that optical stimulation of ChR2 opsin-expressing hDPSCs leads to active the light sensitive ion channel and changing the effective RI of the surrounding medium. The neural activity is driven by changes in intracellular and extracellular ion concentrations, which lead to alterations in the RI of the cell medium RI variations detectable by the sensor. The novel sensor structure demonstrated its ability to detect RI changes in the cell medium during optogenetic stimulation and fiber optic sensors can be a good candidate for optical recording of the neural activity. Beyond these in vivo applications, label free fiber optic biosensors-based IR measurement can be used for all optical multifunctional probe in stimulation, recording, and sensing of neuroscience applications.

Fiber optic localized surface plasmon resonance (LSPR) sensors have become an effective tool in refractive index (RI) detection for biomedical applications because of their high sensitivity. However, using conventional optical fiber has caused limitations in implanting the sensor in the body. This research presents the design and construction of a new type of polymer-based LSPR sensors to address this issue. Also, finite element method (FEM) is used to design the sensor and test it theoretically. The proposed polymer optical fiber (POF) based on citrate is biocompatible, flexible, and degradable, with a rate of 22% and 27 over 12 days. The step RI structure utilizes two polymers for light transmission: poly (octamethylene maleate citrate) (POMC) as the core and poly (octamethylene citrate) (POC) as the cladding. The POF core and cladding diameters and lengths are 700 µm, 1400 µm, and 7 cm, respectively. The coupling efficiency of light to the POF was enhanced using a microsphere fiber optic tip. The obtained results show that the light coupling efficiency increased to 77.8%. Plasma surface treatment was used to immobilize gold nanoparticles (AuNPs) on the tip of the POF, as a LSPR-POF sensor. Adsorption kinetics was measured based on the pseudo-first-order model to determine the efficiency of immobilizing AuNPs, in which the adsorption rate constant (k) was obtained be 8.6 × 10–3 min−1. The RI sensitivity of the sensor in the range from 1.3332 to 1.3604 RIU was obtained as 7778%/RIU, and the sensitivity was enhanced ~ 5 times to the previous RI POF sensors. These results are in good agreement with theory and computer simulation. It promises a highly sensitive and label-free detection biosensor for point-of-care applications such as neurosciences.

In this paper, a fiber-optic Fabry-Perot microcavity sensor is presented based on splicing a catastrophic fused fiber (CFF) to a single-mode fiber (SMF) for the simultaneous measurement of the refractive index (RI) and temperature. CFF formed by the catastrophic fuse effect consists of a periodic void in the fiber core that creates a teardrop shape or elliptical air microcavity after splicing. By simulation, the elliptical microcavity sensor is selected to measure external RI changes by Fast Fourier Transform (FFT) analysis. The RI sensitivity was obtained to be -2.5 +/- 0.0074/RIU with a resolution of about 4 x 10(-5) RIU. Also, the experimental results showed that temperature is obtained independently from the FFT parameter without being affected by the RI. The sensor temperature was determined by tracking the wavelength shift of the interference spectrum. Consequently, the temperature sensitivity of 7 pm/degrees C in the range of 20 degrees C to 95 degrees C was achieved. Therefore, the RI and the temperature were simultaneously measured by analyzing the spatial frequency and wavelength shift. The proposed dual-microcavity FP sensor can compensate for any power fluctuation in the input light source.

A Fabry-Perot cavity milled with a focused ion beam on a tapered fiber tip is proposed for in vivo neural activity recording as an optical method. Optical fiber micro-tips are good candidate devices for sensing applications in a small volume and difficult to access locations, such as neuroscience research. The fiber-based probe is electrical artifact-free, labeling free, and feasible for a portable system compared with conventional in vivo neural recording networks. Optical signals and electrical neural activity from the rat somatosensory cortex were simultaneously recorded. This fiber-based probe promises the enhanced ability to extracellular recording of the neural activity in neurophotonics applications. It has a potential capability compared with optrode in optogenetics techniques. Therefore, a single fiber optic probe can be used for simultaneous optical stimulation and optical recording.

Birefr ingence measurement is an important proper ties of optical mater ial in optical area. Compared with conventional birefr ingence measurement method, a novel birefr ingence measurement method of ferro-fluid is presented using non-adiabatic tapered fiber optic in fiber loop mir ror configuration. Simulation and experiment were done to prove the effective of measurement system. Also, the birefr ingence of ferro-fluid in the range from 0 to 29.48 mT was obtained equal to 0-3.510. This structure has great potential in the optical sensing area and biomedical applications as drug delivery.

A high-birefringent fiber loop mirror (HB-FLM) setup was used as an optical refractometer by inserting a tapered high-birefringence fiber (THB) in to the FLM setup. The response of the THB-FLM is analyzed theoretically and experimentally. The sensitivity of the THB-FLM sensor temperature is -0.40 nm/ ̊C. The proposed sensor has such advantages as low temperature sensitivity, simple structure, and ease of fabrication. It also indicates that the FLM sensor based on THB is helpful to reduce temperature crosssensitivity for the measurement of environment and biomedical parameters.

In this study, an optical signal recording method for optogenetics stimulation of ChR2 channels expressed in human pulp dental (HPD) cells by using a fiber optic refractive index (RI) sensor based on all fiber Mach-Zehnder interferometer was proposed. All-fiber Mach-Zender interferometric biosensor is composed of a specially fabricated twin-core fiber spliced between two pieces of a single-mode fiber which one of the cores was doped with germanium and the other with phosphorous [1]. The interference pattern in the fiber Mach-Zehnder interferometer is occurred by coupling of the propagation lights of both fiber cores. For coupling the light into both cores, a short length of a coreless fiber optic was used. The length of twin-core fiber was 40 cm. Here, one core of the fiber acts as a reference arm and the other cores as sensing arm. For increasing evanescent wave around the sensing arm of the fiber optic biosensor, a short section of the cladding of the twin-core fiber about 2 cm was etched with HF solution. For this propose, after determining the direction of the cores so that the two cores were in the vertical direction, one side of the twin-core fiber was fixed on Plexiglas substrate by using UV glow and the upper side of the sensor was etched. The thickness of remained clad around the upper core was about 1 micrometer. In the experimental setup as is shown in Fig. 1(a), light from an SLD at 1550 nm after passing an isolator arrived at the sensor and output spectrum was monitored with an optical spectrum analyzer which has 10 pm wavelength resolution. The best RI sensitivity of the sensor in the range of 1.39 to 1.43 was obtained to be 675.74 nm/RIU. For detecting of cell signal by using optogenetic stimulation which ChR2 opsin was expressed on HPD cells, it needs that high concentrations of cells were immobilized to the etched fiber surface by PLL biopolymer. Optogenetic stimulation of ChR2 channel was done using a 470 nm laser diode [2] pulse with a frequency of 15 Hz, a number of pulses 120, duty cycle 50 in 60 seconds, and 300 second rest time. As a result of optogenetic stimulation and activation of light-sensitive ion channels, effective RI around the fiber optic biosensor changes [3]. Obtained results were shown in Fig. 1(b). Changes in the RI lead to a wavelength shift of the sensor spectrum.

This paper proposes and investigates a partial discharge (PD) detector based on fiber Bragg grating (FBG) sensor and a mandrel to detect and localize PD in power transformers. An identification of PD in the early stages is important, so using high-resolution sensor is considerable. A Teflon hollow mandrel with attached FBG is chosen as the inner transformer PD detector. The design of the sensor in terms of materials, dimensions, and the shape is chosen; it receives signal strength according to the obtained distance and angle. Standard deviation of angle data is <0.4 mV and as the distance increases, the received signal strength decreases exponentially and oscillatory. Simulation results verify the performance of the proposed sensor in the detection of the transformer PD signals. The proposed sensor is experimentally tested. It succeeded in detecting PD, and can simultaneously detect four frequencies of acoustic signal in the range of 14 to 350 kHz, which is superior to similar sensors. (C) 2018 Society of Photo-Optical Instrumentation Engineers (SPIE).

نیا تیاس رد هک تسا رابتعا یاراد یتروص رد هلاقم www.opsi.ir دشاب یسرتسد لباق لخادت ساسا رب یرمیلپ یرون ربیف رگسح هلاقم نیا رد ئارا ورپ یرباف جنس ،ناسآ تخاس ،ییامد یلااب تیساسح .تسا هدش ه هزادنا یم رگسح نیا یایازم زا ندوب مکحم و کچوک ی هناوتسا کی رگسح نیا یلصا راتخاس .دشاب سنج زا PDMS یرون ربیف رس هک تسا کی هناوتسا نیا نورد و هتفرگ رارق دم کت یبیرقت لوط هب اوه فاگ 200 یا رتمورکیم .تسا هدش داج اب و هیروف لیدبت زا هدافتسا کیکفت اکرف سن یاضف هب طوبرم ی کاواک ، تیساسح ییامد رگسح اب ربارب nm/°C 15 دمآ تسد هب .

A magnetic field vector sensor based on super-paramagnetic fluid and tapered Hi-Bi fiber (THB) in fiber loop mirror (FLM) is proposed. A two-dimensional detection of external magnetic field (EMF) is experimentally demonstrated and theoretically simulated by Jones matrix to analyze the physical operation in detail. A birefringence is obtained due to magnetic fluid (MF) in applied EMF. By surrounding the THB with MF, a tunable birefringence of MF affect the transmission of the sensor. Slow and fast axes of this obtained birefringence are determined by the direction of applied EMF. In this way, the transmission response of the sensor is depended on the angle between the EMF orientation and the main axes of polarization maintaining fiber (PMF) in FLM. The wavelength shift and intensity shift versus EMF orientation show a sinusoidal behavior, while the applied EMF is constant. Also, the changes in the intensity of EMF in a certain direction results in wavelength shift in the sensor spectrum. The maximum wavelength sensitivity of 214 pm/mT is observed. (C) 2017 Elsevier Ltd. All rights reserved.

The linear birefringence (LB) is caused by the different phase retardation (retardance) of two linearly polarized eigenstates of light passing through the material. Birefringence was a significant parameter of an optical material in optical area. Compared with the traditional birefringence measurement method such as modulation technique, a novel birefringence measurement method of magnetic fluid (MF) using all optical fiber based on a Hi-Bi non-adiabatic tapered optical fiber (HBT) sensor in fiber loop mirror (FLM) was proposed in this letter. The sensitivity and detection limit of the sensor in this set up was enhanced. Moreover, it was stability, strong resistance to disturbance, easy assembly, and achievement.

A magnetic field fiber optic sensor based on Nano-magnetic fluid and Hi-Bi non-adiabatic tapered optical fiber in fiber loop mirror (HB-TFLM) is proposed and theoretically explained. As compared to the reported magnetic fluid (MF) based sensors, the achieved sensitivity of the proposed sensor is 255 pm/mT, which is enhanced by 3.6 times of magnitude relative to in line non-adiabatic tapered optical fiber sensor, used only 0.1% of the volume concentration of MF nanoparticles. Detection limit of the HB-TFLM to external magnetic field in range from 0 to 21 mT and 22 to 50 mT was 7.8 μT and 39.2 μT, respectively.

An external magnetic field (EMF) fiber sensor by combining nanomagnetic fluid and Hi-Bi nonadiabatic tapered optical fiber in fiber loop mirror (THB-FLM) is demonstrated experimentally and theoretically. The polarization controllers (PCs) in FLM are adjusted to excite different cladding modes in the sensor. By variation of the PCs' settings, the sensitivity of the sensor to EMF in the range from 0 to 21 mT could be tuned from 255 to 402 pm/mT. As compared to the reported magnetic fluid (MF) based sensors, the achieved sensitivity of the proposed sensor, with only 0.1% of the volume concentration of MF nanoparticles, enhanced by 5.6 orders of magnitude relative to in-line nonadiabatic tapered optical fiber sensor. The detection limit of the THB-FLM to EMF in the range of 0 to 21 mT and 22 to 50 mT was 5 and 18.9 mu T, respectively. Experimental results show that the sensitivity to the EMF increased with the order of the cladding mode. In addition to the EMF sensing capability, the proposed structure can simultaneously provide temperature information.

This paper presents the fiber pressure sensor based on Fabry-Perote interferometry. The design and fabrication of the sensor are based on MEMS technique. The polymer diaphragm analysis was done theoretically. The pressure sensor response is approximately linear in the range from 0 to 51 Kpa at room temperature. For sensor with 5.5mm and 3.5 mm diaphragm thickness, the sensitivities are -466 nm/Kpa and -654 nm/Kpa with limit of detection of 6×50-3 Pa and 4×50-3Pa, respectively. Also, the young’s modulus and resonance frequency of diaphragm was calculated according to experimental results. The simple fabrication, small size, and linear response make the sensor suitable for many industrial applications.