Operando monitoring of thermal runaway in commercial lithium-ion cells via advanced lab-on-fiber technologies.

Operando monitoring of complex physical and chemical activities inside rechargeable lithium-ion batteries during thermal runaway is critical to understanding thermal runaway mechanisms and giving early warning of safety-related failure. However, most existing sensors cannot survive during such extremely hazardous thermal runaway processes (temperature up to 500 °C accompanied by fire and explosion). To address this, we develop a compact and multifunctional optical fiber sensor (12 mm in length and 125 µm in diameter) capable of insertion into commercial 18650 cells to continuously monitor internal temperature and pressure effects during cell thermal runaway.

Recovery of a highly reflective Bragg grating in DPDS-doped polymer optical fiber by thermal annealing.

We report fiber Bragg grating manufacturing in poly(methyl methacrylate) (PMMA)-based polymer optical fibers (POFs) with a diphenyl disulfide (DPDS)-doped core by means of a 266 nm pulsed laser and the phase mask technique. Gratings were inscribed with different pulse energies ranging from 2.2 mJ to 2.

Polymeric fiber sensors for insertion forces and trajectory determination of cochlear implants in hearing preservation.

The level of hearing restoration in patients with severe to profound sensorineural hearing loss by means of cochlear implants (CIs) has drastically risen since the introduction of these neuroprosthetics. The proposed CI integrated with polymer optical fiber Bragg gratings (POFBGs) enables real-time evaluation of insertion forces and trajectory determination during implantation irrespective of the speed of insertion, as well as provides high signal quality, low stiffness levels, minimum induced stress even under forces of high magnitudes and exhibits significant reduction of the risk of fiber breakage inside the constricted cochlear geometry. As such, the proposed device opens new avenues towards atraumatic cochlear implantations and provides a direct route for the next generation of CIs with intraoperative insertion force assessment and path planning capacity crucial for surgical navigation.

Accelerated pyro-catalytic hydrogen production enabled by plasmonic local heating of Au on pyroelectric BaTiO nanoparticles.

The greatest challenge that limits the application of pyro-catalytic materials is the lack of highly frequent thermal cycling due to the enormous heat capacity of ambient environment, resulting in low pyro-catalytic efficiency. Here, we introduce localized plasmonic heat sources to rapidly yet efficiently heat up pyro-catalytic material itself without wasting energy to raise the surrounding temperature, triggering a significantly expedited pyro-catalytic reaction and enabling multiple pyro-catalytic cycling per unit time. In our work, plasmonic metal/pyro-catalyst composite is fabricated by in situ grown gold nanoparticles on three-dimensional structured coral-like BaTiO nanoparticles, which achieves a high hydrogen production rate of 133.

Ultraminiature optical fiber-tip directly-printed plasmonic biosensors for label-free biodetection.

Miniaturization of biosensors has become an imperative demand because of its great potential in in vivo biomarker detection and disease diagnostics as well as the point-of-care testing for coping with public health crisis, such as the coronavirus disease 2019 pandemic. Here, we present an ultraminiature optical fiber-tip biosensor based on the plasmonic gold nanoparticles (AuNPs) directly printed upon the end face of a standard multimode optical fiber at visible light range. An in-situ precision photoreduction technology is developed to additively print the micropatterns of size-controlled AuNPs.

PCF based modal interferometer for lead ion detection.

A compact, reliable, and fast responsive PCF (photonic crystal fiber) based modal interferometric sensor for lead ion detection is proposed and experimentally demonstrated. The sensor has been fabricated by splicing a small section of PCF with SMF (single mode fiber) followed by collapsing the air holes of PCF at its tip. The interferometer is dip coated with chitosan-PVA (polyvinyl alcohol) and glutathione functionalized gold nanoparticles.

Femtosecond laser point-by-point Bragg grating inscription in BDK-doped step-index PMMA optical fibers.

In this paper, the inscription of 2-mm-long fiber Bragg gratings (FBGs) on benzyl dimethyl ketal (BDK)-doped poly(methyl methacrylate) (PMMA) optical fibers by means of a femtosecond laser and a point-by-point FBG inscription technique is reported. The highest reflectivity of approximately 99% is obtained with a pulse energy of 68.5 nJ, showing a large refractive index modulation amplitude of 7.

Large refractive index modulation based on a BDK-doped step-index PMMA optical fiber for highly reflective Bragg grating inscription.

We experimentally report high reflectivity on the poly(methyl methacrylate) (PMMA)-based polymer optical fiber Bragg gratings by means of a 266 nm pulsed laser and phase mask technique. In the first recipe, fiber Bragg gratings (FBGs) were manufactured with a single pulse up to 3.7 mJ.

Random forest assisted vector displacement sensor based on a multicore fiber.

We proposed a two-dimensional vector displacement sensor with the capability of distinguishing the direction and amplitude of the displacement simultaneously, with improved performance assisted by random forest, a powerful machine learning algorithm. The sensor was designed based on a seven-core multi-core fiber inscribed with Bragg gratings, with a displacement direction range of 0-360° and the amplitude range related to the length of the sensor body. The displacement information was obtained under a random circumstance, where the performances with theoretical model and random forest model were studied.

Pattern recognition in distributed fiber-optic acoustic sensor using an intensity and phase stacked convolutional neural network with data augmentation.

Distributed acoustic sensors (DASs) have the capability of registering faint vibrations with high spatial resolution along the sensing fiber. Advanced algorithms are important for DAS in many applications since they can help extract and classify the unique signatures of different types of vibration events. Deep convolutional neural networks (CNNs), which have powerful spectro-temporal feature learning capability, are well suited for event classification in DAS.

Low gas pressure sensor based on a polymer optical fiber grating.

A fiber Bragg grating (FBG) inscribed Zeonex-based novel, to the best of our knowledge, side hole polymer optical fiber (SHPOF) is proposed and demonstrated for low gas pressure measurement above and below the atmospheric pressure. Two different grades of Zeonex have been used to fabricate the core and cladding of this fiber, thereby making it dopant free. The side hole introduced in the cladding is parallel to the fiber core.

Hydrogel based Fabry-Pérot cavity for a pH sensor.

A simple, reliable, and quick reactive Fabry-Pérot (FP) structure-based fiber optic pH sensor is presented. The pH-sensitive hydrogel and single-mode fiber (SMF) are placed inside a fused silica capillary to form the FP cavity. The gel thickness is characterized by the spin coating method with respect to different spin speeds.

Simultaneous measurement of temperature and strain based on a hollow core Bragg fiber.

A novel, to the best of our knowledge, reflective sensor fabricated by simply sandwiching a homemade hollow core Bragg fiber (HCBF) between two single-mode fibers is proposed and demonstrated for the simultaneous measurement of the temperature and the strain. Different from traditional Fabry-Perot interferometer (FPI) sensors that can achieve only one-parameter sensing with inevitable cross-correspondence to other parameters, the proposed sensor based on the HCBF, which functions as an FPI-inducing FPI spectrum pattern and a weak waveguide confining light-inducing periodic envelope in reflection spectrum, ensures double-parameter sensing. For the HCBF-based reflective sensor, different sensing mechanisms lead to the various sensitivity values of temperature and strain (2.

Two semicircular-hole fiber in a Sagnac loop for simultaneous discrimination of torsion, strain and temperature.

We report a highly sensitive twist sensor based on a Sagnac interferometer constructed with a new type of optical fiber which contains an elliptical core and two large semicircular-holes, where the slow axis of the core orthogonal to the air-holes has a large sensitivity towards twist-induced birefringent changes. The novel fiber structure results in a highest twist sensitivity of 5.01 nm/° at a chosen dip over the range from 370°-400°.

Single nanosecond-pulse production of polymeric fiber Bragg gratings for biomedical applications.

In this study, we present first-time fabrication of FBGs in all ZEONEX-based SMPOFs with a single 25 ns pulse of 248 nm UV irradiation over a 12-month period, which opens up new frontiers in optics and photonics for the effective fabrication of polymer optical fiber Bragg gratings (POFBGs), permitting mass producibility of them. POFBGs were characterized by subjecting them to various physical parameters including temperature and tensile strain. Strain responses of FBGs with similar grating strengths fabricated with 248 nm and 325 nm He-Cd laser irradiations were explored over a year to demonstrate their long-term stability and applicability.

Sensitive Mach-Zehnder interferometric sensor based on a grapefruit microstructured fiber by lateral offset splicing.

A novel inline Mach-Zehnder interferometric (MZI) sensor based on a homemade grapefruit microstructured fiber (GMF) was proposed and experimentally demonstrated. The sensing unit consists of a short segment of a GMF sandwiched between two single mode fibers using lateral offset splicing. The fabrication of the GMF and the GMF-based MZI sensor was introduced.

Silicone Rubber Based Highly Sensitive Fiber-Optic Fabry-Perot Interferometric Gas Pressure Sensor.

A simple, compact, and highly sensitive gas pressure sensor based on a Fabry-Perot interferometer (FPI) with a silicone rubber (SR) diaphragm is demonstrated. The SR diaphragm is fabricated on the tip of a silica tube using capillary action followed by spin coating. This process ensures uniformity of its inner surface along with reproducibility.

All-optical fiber filter based on an FBG inscribed in a silica/silicone composite fiber.

An all-optical tunable filter based on a fiber Bragg grating (FBG) inscribed in a self-heated silica/silicone composite fiber is demonstrated. A thin silicone film is coated inside the suspended core fiber), which acts as the silicone cladding. A periodic refractive index modulation is inscribed in the silicone cladding by UV irradiation.

Application of Fibre Bragg Grating Sensors in Strain Monitoring and Fracture Recovery of Human Femur Bone.

Fibre Bragg Grating (FBG) sensors are gaining popularity in biomedical engineering. However, specific standards for in vivo testing for their use are absolutely limited. In this study, in vitro experimental tests were performed to investigate the behaviors and applications of gratings attached to intact and fractured thighbone for a range of compression loading (<300 N) based around some usual daily activities.

Ultracompact optical fiber acoustic sensors based on a fiber-top spirally-suspended optomechanical microresonator.

Acoustic wave sensors with a high sensitivity and small size are highly desired for a wide variety of important and emerging applications such as photoacoustic gas sensing and bio-imaging. Here we present an ultracompact optical fiber acoustic sensor based on an optomechanical resonator that is directly in situ printed on the end face of a standard single-mode optical fiber by using an optical 3D μ-printing technology. The fiber-top optomechanical microresonator is composed of a microscale suspended polymer micro-disk that forms a Fabry-Perot interferometric cavity, together with the optical fiber end face, and acts as the acoustic wave-sensitive micromechanical resonator simultaneously.

Ultrasensitive optofluidic enzyme-linked immunosorbent assay by on-chip integrated polymer whispering-gallery-mode microlaser sensors.

Optical whispering-gallery-mode (WGM) microcavities offer great promise in ultrasensitive biosensors because of their unique ability to enable resonant recirculation of light to achieve strong light-matter interactions in microscale volumes. However, it remains a challenge to develop cost-effective, high-performance WGM microcavity-based biosensing devices for practical disease diagnosis applications. In this paper, we present an optofluidic chip that is integrated with directly-printed, high-quality-factor (Q) polymer WGM microlaser sensors for ultrasensitive enzyme-linked immunosorbent assay (ELISA).

Microstructured optical fiber based Fabry-Pérot interferometer as a humidity sensor utilizing chitosan polymeric matrix for breath monitoring.

This study reports a method for humidity sensing based on a specialty microstructured optical fiber (MOF). A suspended tri-core MOF was fabricated using the stack and draw technique. A low finesse sensing head was prepared by depositing a chitosan polymer matrix within the holes of the MOF, forming a Fabry-Pérot interferometer as a sensing platform while the chitosan film acts as the sensing material.

Resurgent regenerated fiber Bragg gratings and thermal annealing techniques for ultra-high temperature sensing beyond 1400°C.

We report for the first time the resurgence of regenerated fiber Bragg gratings (RFBGs) useful for ultra-high temperature measurements exceeding 1400 °C. A detailed study of the dynamics associated with grating regeneration in six-hole microstructured optical fibers (SHMOFs) and single mode fibers (SMFs) was conducted. Rapid heating and rapid cooling techniques appeared to have a significant impact on the thermal sustainability of the RFBGs in both types of optical fibers reaching temperature regimes exceeding 1400 °C.

Impact of high UV fluences on the mechanical and sensing properties of polymer optical fibers for high strain measurements.

PMMA-based fibers are widely studied for strain measurements and show repeatable results for Fiber Bragg Gratings (FBGs) inscribed using 325 nm laser and 248 nm laser. However, there is no available material mechanical behavior characterization of the UV source impact on the fiber properties. In this manuscript, fibers are irradiated with high fluence of 325 nm and 248 nm lasers and the fibers properties are investigated using dynamic mechanical analysis and tensile strain for potential use of these fibers past the yield point.