Fiber Probe Research Articles

Optimising Shifted Excitation Raman Difference Spectroscopy (SERDS) for application in highly fluorescent biological samples, using fibre optic probes.

Fibre optic probe based Raman spectroscopy can deliver in vivo molecular compositional analysis of a range of diseases. However, some biological tissues exhibit high levels of fluorescence which limit the utility of the technique, particularly when the fluorescence induces CCD etaloning, which can be particulalry hard to remove in subsequent analysis. Furthermore, use of fibre probes can result in silica signals superimposed on the biological Raman signals. Shifted excitation Raman difference spectroscopy (SERDS) utilises a small seperation in excitation wavelengths to remove signals from fluorescence, room lights, optical components and etaloning contributions, while retaining chemical signals from the sample. In this study, we sought to measure the optimum SERDS spectra enabling reconstruction of a range a narrow and broad peaks found in biological samples. A original wavelength of 830 nm was utilised with 7 different shifts between 0.4 and 3.9 nm to determine which gave the best performance. This range roughly corresponds to the typical range of peak widths within biological Raman spectra at 830 nm excitation; 0.41 - 3.25 nm or 6 - 47 cm-1. An wavelength shift of 2.4 nm was identified as optimal. Finally, a fibre optic Raman probe was used to measure 2 human lymph nodes ex vivo to demonstrate the feasibility of the approach with real-world examples.

Easy networking enhanced quantum wires-based fiber probe for highly sensitive NH3 gas detection at room temperature

Easy networking enhanced quantum wires-based fiber probe for highly sensitive NH3 gas detection at room temperature

An optical carbon nanotube fibre probe for measurement of nano structures with large aspect ratio

An optical carbon nanotube fibre probe for measurement of nano structures with large aspect ratio

Clinical confocal laser endomicroscopy for imaging of autofluorescence signals of human brain tumors and non-tumor brain

PurposeAnalysis of autofluorescence holds promise for brain tumor delineation and diagnosis. Therefore, we investigated the potential of a commercial confocal laser scanning endomicroscopy (CLE) system for clinical imaging of brain tumors.MethodsA clinical CLE system with fiber probe and 488 nm laser excitation was used to acquire images of tissue autofluorescence. Fresh samples were obtained from routine surgeries (glioblastoma n = 6, meningioma n = 6, brain metastases n = 10, pituitary adenoma n = 2, non-tumor from surgery for the treatment of pharmacoresistant epilepsy n = 2). Additionally, in situ intraoperative label-free CLE was performed in three cases. The autofluorescence images were visually inspected for feature identification and quantification. For reference, tissue cryosections were prepared and further analyzed by label-free multiphoton microscopy and HE histology.ResultsLabel-free CLE enabled the acquisition of autofluorescence images for all cases. Autofluorescent structures were assigned to the cytoplasmic compartment of cells, elastin fibers, psammoma bodies and blood vessels by comparison to references. Sparse punctuated autofluorescence was identified in most images across all cases, while dense punctuated autofluorescence was most frequent in glioblastomas. Autofluorescent cells were observed in higher abundancies in images of non-tumor samples. Diffuse autofluorescence, fibers and round fluorescent structures were predominantly found in tumor tissues.ConclusionLabel-free CLE imaging through an approved clinical device was able to visualize the characteristic autofluorescence patterns of human brain tumors and non-tumor brain tissue ex vivo and in situ. Therefore, this approach offers the possibility to obtain intraoperative diagnostic information before resection, importantly independent of any kind of marker or label.

Photon efficacy and cost investigation of LEDs at different wavelengths and color temperatures for horticulture

Photon efficacy (PE) is defined as the photon numbers generated by 1 joule (J) of power consumption, which is a key indicator on energy efficiency of LED lighting. PE calculated by LED datasheet includes photons irradiating in all directions, therefore deviates far from the actual PE of LED grow lights in indoor farms where only photons shining on plants are counted. To measure the PEs of different types of LEDs for plant growth accurately, we designed and fabricated LED panels for 16 types of LEDs at different wavelengths and color temperatures under plant growth conditions. We characterized the LED panels by an optical spectroscopy setup, in which an optical fiber probe mapped the optical spectra of LEDs on the plant growth area to detect the photon numbers reachable to plants. We found that at plant growth conditions, the LED panels at 660, 730 and 450 nm have higher PEs of 3.84, 3.39 and 2.38 µmol/J, respectively, followed by 2.31, 2.08 and 2.03 µmol/J for white LEDs at the color temperatures of 5700 K, 5000 K and 4000 K, respectively. We further compared the LED costs and concluded that 4000 K, 3000 K, 475 nm and 5700 K LED panels are most cost-effective to build at an LED cost of 0.15-0.21 US$ per µmol/s. Our findings provide a good reference for plant scientists and horticulture practitioners to understand LED lighting cost at different wavelengths and color temperatures for plant growth, for them to develop the lighting recipes effectively and estimate farm operating cost more precisely.

Direct laser micro-drilling of high-quality photonic nanojet achieved by optical fiber probe with microcone-shaped tip

Photonic nanojet can serve as a powerful tool for direct laser micro-machining based on a non-resonance focusing phenomenon. In this study, we propose a photonic nanojet-based direct micro-drilling technique for polymer material with low-cost and low-power continuous-wave laser. The high-quality photonic nanojet is produced using the microcone-shaped probe tip, which is fabricated by the dynamic chemical etching method. By utilizing laser photonic nanojet triggered thermoplasmonics, the high-aspect-ratio microcavity is fabricated with the low threshold value of laser power. The influences of the photonic nanojet peak intensities and distributions on the drilled microcavities are systematically investigated by the experiments and the finite-difference time-domain simulations. With the continuous-wave solid-state laser at a wavelength of 671 nm, the simulations show that the photonic nanojet with a quality factor of 103 is generated at a distance of ~ 20 μm from the surface of the microcone-shaped tip with a beam waist of 252 nm in the x direction, which could overcome the diffraction limit. The experimental results show that the length and peak intensity of the photonic nanojet have increased considerably in the propagation direction by the microcone-shaped probe tip, which leads to form a deep microcavity in the polymer substrate with an aspect ratio of 5.73. The presented microcone-shaped probe tip has potential applications in processing sub-diffraction features with a high aspect ratio.

Sensitivity analysis of bent sensing elements of the fiber probes for mid-IR spectroscopy

Sensitivity analysis of bent sensing elements of the fiber probes for mid-IR spectroscopy

In-situ synthesis and integration of gold nanoparticles into 3D printed optical fiber probes

This work uses the polymeric reduction method to explore the in-situ synthesis of gold nanoparticles (AuNPs) within 3D-printed optical fiber probes (OFPs). Digital light processing (DLP) 3D printing is employed to fabricate the OFPs using a resin consisting of hydroxyethyl methacrylate (HEMA) and polyethylene glycol diacrylate (PEGDA). After printing, OFPs were immersed in a boiling gold precursor solution to facilitate the synthesis of AuNPs inside the polymer matrix. We produced single material (HEMA/PEGDA) and multimaterial (HEMA/PEGDA + Dentaclear) OFPs loaded with AuNPs at different concentrations. Scanning electron microscopy analysis confirmed the effective distribution and dispersion of AuNPs within the polymer matrix. The optical properties, including reflection and transmission spectra, are comprehensively measured using customized setups. The localized surface plasmon resonance of the embedded AuNPs created a distinct dip in the 500–600 nm wavelength range. Higher AuNP concentrations and longer dipping times enhanced light absorption, reducing reflection and transmission intensities. Multimaterial OFPs also exhibited tunable wavelength filtering capabilities based on the AuNP concentration. The AuNP-loaded OFPs demonstrated stable optical performance across varying temperatures and pH environments, highlighting their potential for diverse applications.

Biofluorometric Ear-Gas Sensing for Non-Invasive Monitoring of Blood EtOH

Exhaled breath and transcutaneous gas contain volatile organic compounds (VOCs) from blood [1]. Some of these blood VOCs are the resultant products of diseases or metabolisms, which has been attracting significant attention to utilize these VOCs for non-invasive and simple disease screening and metabolism assessment [2,3]. Transcutaneous gas is more suitable to real-time and continuous assessment than breath. Especially, the external ear region has skin with a lower density of sweat glands (140 spots/cm2) compared to other regions of the body, such as the palm, forearm, and cheek. Also, gas from the external ear is not only from an outer part of the external ear but also from the external ear canal. In addition, the external ear has a relatively large space to incorporate devices to measure. In this study, a headset-type ear-gas sensing system including a bio-fluorometric gas sensor has developed using ADH (alcohol dehydrogenase) for external ear-derived EtOH, then the system was applied for continuous measurement of EtOH at the external ear after drinking.The gas monitoring system was developed by combining an over-ear gas collection cell and a biofluorometric gas sensor for EtOH vapor. Alcohol dehydrogenase (ADH) catalyzes the oxidation of EtOH to produce acetaldehyde. Simultaneously, a coenzyme, oxidized form of β-nicotinamide adenine dinucleotide (NAD+), accepts the electron to become the reduced form (NADH) that exhibits autofluorescence (λex=340 nm, λfl=490 nm); therefore, EtOH can be measured by detecting the increase in the autofluorescence from NADH. An enzyme-immobilized membrane (ADH membrane) attached to the flow-cell worked as a gas-liquid diaphragm. When the EtOH vapor reaches the ADH membrane, the catalyzed redox reaction occurs at the membrane together with NAD+ in the buffer solution running above the membrane, which produces NADH in the buffer solution. The resultant NADH was excited by the UV light from the optical fiber, then the emitted fluorescence was collected by the same fiber probe to be detected. In the monitoring of external ear-gas, the sample gas from a subject was collected by the headset type gas collection cell, and then simultaneously transported to the biofluorometric gas sensor for real-time measurement. The gas sensor was composed of excitation and detection units which were connected to a bifurcated optical fiber. The excitation unit has a UV-LED (340 nm) and a bandpass filter (BPF) to make the peak wavelength of the excitation light 340 nm. The detection unit has a photomultiplier tube (PMT) and another BPF to extract fluorescence light from NADH. The flow cell made of PMMA is attached to an optical fiber probe end, that is connected to the bifurcated optical fiber. ADH membrane was attached and fixed at the end of the flow cell by an o-ring. ADH was immobilized by entrapping in a hydrophilic PTFE membrane with poly[2-methacryloyloxyethyl phosphorylcholine (MPC)-co-2-ethylhexyl methacrylate (EHMA)] (PMEH). The sensitivity of the ADH gas sensor and the reproducibility of the sensor output for various ethanol concentrations were investigated. The sensor output was dependent on the concentration of gaseous EtOH. The dynamic range of the ADH gas sensor is 10 ppb-554 ppm of EtOH vapor. The biofluorometric gas sensor indicated the high selectivity, relying on ADH specificity, to gaseous EtOH.The biofluorometric EtOH gas sensor was applied for ear gas sensing.The over-ear gas collection cell was fabricated by modifying a commercial earmuff with two connectors for filtered air (carrier gas) and for sample gas containing ear gas, respectively. Real-time and continuous measurement of external ear-derived EtOH was conducted for healthy subjects with alcohol intake (Approval No. M2018-160 at Tokyo Medical and Dental University). As the results of the ear gas monitoring for the subjects. The EtOH concentration from the external ear started to rise a few minutes after drinking and reached the peak (approx. 100 ppb) 50 minutes later, then the EtOH concentration gradually decreased. This temporal change has a similarity to that of breath EtOH concentration with a few minutes time-delay. According to other reports proving that EtOH concentrations in blood and breath correlate, the concentration of the external ear’s EtOH is most likely correlated to that in blood. In this study, the headset type ear gas sensor successfully measured the transcutaneous ear EtOH-related blood one after drinking. In the future, the ear-gas sensor will be applied to other blood VOCs monitoring for non-invasive assessment of metabolisms and disease conditions that require detailed and real-time information.

An improved method to process the data of optical Fiber signals for identifying the instantaneous flow structure in a gas-solid fluidized bed

The instantaneous signals recorded with the optical fiber probe (OFP) directly reflect the hydrodynamic behaviors in fluidized beds. A new data-processing method is put forward to calculate the threshold voltage that is used to discern the bubble phase and emulsion phase. It is found that the threshold voltage is not only related to the flow pattern but also to the color of the used particles. Then the data-processing programs including the Fast Fourier filter have been developed for determining the flow characteristics such as the bubble/particle velocity, bubble/agglomerations chord length, etc. By comparing them with other different methods, the suitability of the proposed method for quantifying the hydrodynamic behaviors in bubble/turbulent fluidized beds is verified. Finally, this method is employed to analyze the characteristics of bubbles, agglomerations and particles in a gas-solid fluidized bed. It is found that the hydrodynamic behaviors of bubbling beds and turbulent beds have significant differences.

Accurate measurement of wavelength-Dependent beam parameters of a supercontinuum light source focused by a lensed fiber probe

In this work, an supercontinuum (SC) light is focused by an optical lensed fiber (OLF). We demonstrate a new method to meticulously analyze multi-wavelength beam parameters of the OLF probe and the focused SC beam by applying a spectrometer to measure the variation of back-coupling efficiency for different wavelengths. By contrast, inevitable and relatively small errors in the OLF parameters that are obtained by using the conventional method lead to significant errors in the spatial information of the focused SC beam. Therefore, this method is expected to be a necessary calibration procedure for a system with an OLF probe. The SC beam focused by our OLF has little chromatic aberration in the beam size and the focal length in a range of approximately 120 μm.

Use of a Single-Fiber Optical Probe for the Detection of Tumor Fluorescence in High-Grade Glioma.

High-grade glioma (HGG) is the most common primary brain tumor in adults. The overall median survival is between 14 and 16 months. Fluorescence-guided surgery by detection of protoporphyrin IX (PpIX) fluorescence has been shown to improve the extent of resection, translating to improved progression-free survival. Microscope-based fluorescence detection techniques are associated with several pain points, some of which may be addressed by using contact-based spectroscopy. We aimed to investigate the accuracy of an optical fiber at detecting PpIX fluorescence by performing real-time spectroscopy in patients with HGG. Adult patients undergoing fluorescence-guided surgery for suspected HGG were recruited prospectively. Intraoperatively, samples from cortex, white matter, and tumor were taken. These samples were interrogated using standard white and blue light microscope techniques and the optical fiber. These specimens were then assessed by neuropathology to determine whether the tumor tissue was present within them. We collected 89 samples from 28 patients. There was an equal ratio of men to women, with a median age of 66.5 years. The accuracy of the probe for detecting PpIX fluorescence was 75.9%, compared with 56.6% for the operating microscope, with a significant improvement in sensitivity (χ2 = 11.84, P < .001). The optical fiber probe was more accurate than the operating microscope for detecting PpIX fluorescence. This technology has potential value in improving the accuracy of fluorescence-guided surgery and has potential practical benefits relating to surgical workflow.

Simple and Efficient Laser-Induced Evaporation Assembly Method to Fabricate SERS Optical Fiber Probe for Detection of PAHs

Simple and Efficient Laser-Induced Evaporation Assembly Method to Fabricate SERS Optical Fiber Probe for Detection of PAHs

Numerical Analysis of Optical Fiber Refractive Index in the Miniaturized Graded‐Index Fiber Probe

ABSTRACTWe analyze the impact of the refractive index of optical fibers on the focusing properties of a miniaturized graded‐index (GRIN) fiber probe. The ABCD ray transfer matrix and characteristic parameters are employed to characterize the working distance, focusing spot size, and the depth of field effectively. The three‐dimensional (3‐D) function diagrams and two‐dimensional (2‐D) graphs are used to illustrate the impact of the no‐core fiber (NCF) refractive index and the center refractive index of GRIN fiber on the focusing properties. Numerical analysis results show that when the length of the NCF is 0.36 mm and the GRIN fiber is 0.1 mm, the variation of the refractive index of the NCF between 1.44 and 1.52 leads to the variation of the working distance in the range of 0.02 mm, while the focusing spot size varies in the range of 5 μm. A comparison of 12 probe samples reveals that a 0.02 difference in the center refractive index of GRIN fiber could result in a 0.16 mm variation in working distance and a variation in focusing spot size of over 3 μm. The experimental results indicate that alterations in the length of the fibers have a considerable effect on the focusing properties of the probe. In contrast, the range of variation in focusing properties with fiber refractive index is relatively limited.

Upconverting thermal history paint for investigations of short thermal events

The main goal of the work was to develop phosphorescent coating for investigations of surface temperature distribution resulted from short duration and high energy thermal events such as small rocket engine testing. For that purpose, we developed thermal history paint with upconverting Gd2O3: Er3+, Yb3+, Mg2+ nanopowder. The developed paint was heated by Joule effect with precise control over temperature and heating time. Photoluminescence signal of cooled samples was excited with 980 nm laser and collected in automatic manner with use of an optical fibre probe connected to photospectrometer. The results show that irreversible changes of paint emission are temperature and heating time specific for calcination temperatures from 700 °C to 1150 °C. Calibration curves were prepared for heating times of 10, 60 and 180 seconds. Finally, 2D surface temperature samples were determined with use of upconverting thermal history paint and compared to IR camera and pyrometric measurements. The results indicate that uncertainty of temperature measurement below 10 °C was achieved for temperatures above 1000 °C. It has been demonstrated that developed thermal history paint allows for measurements of 2D surface temperature distribution with high spatial resolution and good agreement to standard measurements techniques like thermal camera and pyrometer.

Detection of picometer scale vibration based on the microsphere near-field probe

We introduce an innovative vibration detection method utilizing a microsphere near-field probe, affixed to an optical fiber probe. Notably, when the microsphere probe is positioned at a distance of approximately 100 nm from the vibrating objects, it exhibits a substantial increase in detection sensitivity, enabling the detection vibration as small as 5 pm. This enhancement arises from the strong near-field interaction between the sample and probe, where the evanescent wave dominates. This effect is confirmed for the first-time through both theoretical analysis and experimental validation. This innovative probe has great potential for applications in cellular acoustics, vibrational detection of biomolecules and their complexes, in situ measurements, and imaging of microstructures and nanostructures.

Controlling spatial optical illuminations in optogenetics using an angled optical fiber tip

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° achieving a maximum lateral illumination position of ± 420 μm away from the optical axis and a peak irradiance of 478.5 mW/mm2, 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° to 12.5° 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.

Neural stimulation and modulation with sub-cellular precision by optomechanical bio-dart

Neural stimulation and modulation at high spatial resolution are crucial for mediating neuronal signaling and plasticity, aiding in a better understanding of neuronal dysfunction and neurodegenerative diseases. However, developing a biocompatible and precisely controllable technique for accurate and effective stimulation and modulation of neurons at the subcellular level is highly challenging. Here, we report an optomechanical method for neural stimulation and modulation with subcellular precision using optically controlled bio-darts. The bio-dart is obtained from the tip of sunflower pollen grain and can generate transient pressure on the cell membrane with submicrometer spatial resolution when propelled by optical scattering force controlled with an optical fiber probe, which results in precision neural stimulation via precisely activation of membrane mechanosensitive ion channel. Importantly, controllable modulation of a single neuronal cell, even down to subcellular neuronal structures such as dendrites, axons, and soma, can be achieved. This bio-dart can also serve as a drug delivery tool for multifunctional neural stimulation and modulation. Remarkably, our optomechanical bio-darts can also be used for in vivo neural stimulation in larval zebrafish. This strategy provides a novel approach for neural stimulation and modulation with sub-cellular precision, paving the way for high-precision neuronal plasticity and neuromodulation.

TEMPERATURE MONITORING FOR LASER METAL DEPOSITION USING NEAR-INFRARED SPECTROSCOPY

Temperature monitoring during laser metal deposition (LMD) aids process control to ensure high-quality production. However, the fluctuating emissivity of the melt pool limits the accuracy of the existing non-contact temperature measuring devices. Thus, this work explores a new temperature monitoring technique, where the thermal radiation emitted by the processing zone was collected with a near-infrared (NIR) spectrometer and fitted to Planck's law to determine the temperature. This work has established the optimised angle and distance of the fiber probe from the LMD processing area to maximise the spectral signal acquisition. The temperature determined from the technique was cross-validated with a thermocouple, resulted in a small deviation of 2.39%. The applicability of the spectroscopic method for continuous temperature monitoring of the LMD process has been demonstrated. The optimised placement for the fiber probe end was determined at the 45˚ angle relative to the surface of the substrate and positioned 5 cm away from the molten pool. The temperature during the LMD process decreased gradually then stabilised after approximately 17 mm track length, resembling those reports in prior studies. Our findings support the practicality of the proposed temperature monitoring approach in LMD.

Impact of kV-cone beam computed tomography dose on DNA repair mechanisms: A pilot study

PurposeIn head and neck squamous cell carcinoma (HNSCC), early complications of the radiotherapy (RT) are observed from the beginning of the treatment to a few months after its end. During external radiotherapy treatment, several patient-dependent parameters can cause a modification of the dose distribution compared to the planned distribution due to variation in patient positioning, anatomy, or intra-fractional movements for example. To verify these parameters during treatment sessions, one of the most commonly used solutions is the cone-beam computed tomography (CBCT). Nowadays, the use of CBCT may constitutes a significant part of the total dose at the end of treatment (up to 10 cGy per session) and more often the volume irradiated by imaging is larger than the one irradiated by the treatment, leading to unintentional irradiation of nearby organs.In this study, we asked whether the imaging low dose added to a following fraction dose (2Gy) may affect the biological response in terms of DNA repair. Material and methodsUsing an IVInomad dosimeter and scintillating fiber probes specially designed for this exploratory study, we exposed fibroblasts cells from head and neck cancer (HNC) patients to a CBCT dose followed by a radiotherapy fraction dose. DNA double strand breaks and DNA repair were assessed by immunofluorescence using the biomarkers gamma H2AX (γH2AX) and pATM. ResultsThe median dose of CBCT was measured between 17 to 21 mGy per session. The kinetics of both biomarkers were found to be strongly dependent on the individual factor in radiosensitive patients. For HNC patients, a prior CBCT dose applied few minutes before the 2Gy dose may have a sublinear effect on the DNA repair mechanisms and potentially on observed health tissue toxicity. ConclusionThe preliminary results obtained highlight the importance of individual and tissue factors for recognizing and repairing DSB during a treatment by radiotherapy using CBCT.