Redox-exfoliated layered transition metal dichalcogenides (LTMDs) find many applications in nonlinear optics, displays, and electronics. The investigated redox LTMD suspensions in this work were characterized optically and found to be highly stable due to surface anionic polyoxometalates (POMs), which maintained the separation between sheets by Coulombic repulsion. However, exposure of the uniform suspensions of LTMDs to an electric field led to agglomeration of the TMDs into clumps of the material in a nearly transparent solvent. This was attributed to the electrochemical reduction of the surface anionic POMs. The electrochemical stability of the redox-exfoliated ACN-MoS2 samples was also investigated by cyclic voltammetric measurements, which confirmed the POM reduction process. This study highlights that the stability of the LTMD/POM system can be compromised by the application of a low-intensity electric field and has bearings on its reliability in optoelectronic devices. 

An all-fiber setup to store and retrieve light pulses using electric control is presented. The experiment is based on a Sagnac interferometer with a phase modulator fabricated using a poled fiber with internal electrodes.

In this article, we report on a carbon-coated optical fiber that is suitable to be used simultaneously as a transmission medium and as a sensor. It consists of a standard single mode fiber (SMF) sleeved in two layers of coating, which provide protection and isolation from external elements. The inner layer is made of carbon, whereas the outer is made of polymer. When the fiber is subjected to mechanical stress, the electrical resistance of the carbon layer changes accordingly. The voltage variations caused by the former can be measured with high accuracy and without interfering with the light propagating through the SMF. In this work, the feasibility of this operating principle is demonstrated in a low coherence Michelson interferometer in which electrical and optical signals were measured simultaneously and compared to each other. Results indicate that electrical measurements are as precise as the optical ones and with linear behavior, reaching a sensitivity of 1.582 mV/με and able to detect vibrations down to 100 mHz. © 2024 The Authors

We present an optical fiber-based selective cell picking module capable of picking up and transferring single cells or clusters. Our Lab-in-a-fiber (LIF) module detects labelled cancer cells (MCF-7) and picks them up for further analysis.

We present an optical fiber-based selective cell picking module capable of picking up and transferring single cells or clusters. Our Lab-in-a-fiber (LIF) module detects labelled cancer cells (MCF-7) and picks them up for further analysis. 

We have developed an optical fiber-based module that can select, retrieve, and transfer single cells, and cell clusters. Cell picking and isolation has several applications such as separating circulating tumor cells, isolating single fetal cells for prenatal testing, and others. Our Lab-in-a-Fiber (LiF) module can detect fluorescent cancer cells (MCF-7) from a mixture of labeled and unlabeled cells and pick them up for further analysis. The cells picked up by the fiber show a 90% survival rate on viability tests, making this cell-picking technique an attractive alternative to existing methods. 

We present the design and fabrication of flexible, liquid-filled scintillating fibers for X-ray detection made from silica fibers and silica capillaries. The scintillating fibers were characterized using ultraviolet light exposure and we also performed an experiment demonstrating X-ray detection.

An all-fiber integrated device capable of separating and counting particles is presented. A sequence of silica fiber capillaries with various diameters and longitudinal cavities are used to fabricate the component for size-based elasto-inertial passive separation of particles followed by detection in an uninterrupted continuous flow. Experimentally, fluorescent particles of 1 μm and 10 μm sizes are mixed in a visco-elastic fluid and fed into the all-fiber separation component. The particles are sheathed by an elasticity enhancer (PEO - polyethylene oxide) to the side walls. Larger 10 μm particles migrate to the center of the silica capillary due to the combined inertial lift force and elastic force, while the smaller 1 μm particles are unaffected, and exit from a side capillary. A separation efficiency of 100% for the 10 μm and 97% for the 1 μm particles is achieved at a total flow rate of 50 μL min−1. To the best of our knowledge, this is the first time effective inertial-based separation has been demonstrated in circular cross-section microchannels. In the following step, the separated 10 μm particles are routed through another all-fiber component for counting and a counting throughput of ∼1400 particles per min is demonstrated. We anticipate the ability to combine high throughput separation and precise 3D control of particle position for ease of counting will aid in the development of advanced microflow cytometers capable of particle separation and quantification for various biomedical applications. 

Microfluidics has emerged rapidly over the past 20 years and has been investigated for a variety of applications from life sciences to environmental monitoring. Although continuous-flow microfluidics is ubiquitous, segmented-flow or droplet microfluidics offers several attractive features. Droplets can be independently manipulated and analyzed with very high throughput. Typically, microfluidics is carried out within planar networks of microchannels, namely, microfluidic chips. We propose that fibers offer an interesting alternative format with key advantages for enhanced optical coupling. Herein, we demonstrate the generation of monodisperse droplets within a uniaxial optofluidic Lab-in-a-Fiber scheme. We combine droplet microfluidics with laser-induced fluorescence (LIF) detection achieved through the development of an optical side-coupling fiber, which we term a periscope fiber. This arrangement provides stable and compact alignment. Laser-induced fluorescence offers high sensitivity and low detection limits with a rapid response time making it an attractive detection method for in situ real-time measurements. We use the well-established fluorophore, fluorescein, to characterize the Lab-in-a-Fiber device and determine the generation of ∼ 0.9 nL droplets. We present characterization data of a range of fluorescein concentrations, establishing a limit of detection (LOD) of 10 nM fluorescein. Finally, we show that the device operates within a realistic and relevant fluorescence regime by detecting reverse-transcription loop-mediated isothermal amplification (RT-LAMP) products in the context of COVID-19 diagnostics. The device represents a step towards the development of a point-of-care droplet digital RT-LAMP platform. © 2022, The Author(s).

We present early design and simulation work on a novel X-ray imaging detector. The intent of the FleX-RAY project is to create a digital X-ray detector that is capable of producing high-resolution images, is flexible enough to produce an image on a curved surface, and is capable of self-reporting its final shape. The X-rays will be detected on a sheet of scintillating optical fibers, which will guide the scintillation light to single-photon avalanche photodiodes. This setup allows the electronics and hardware to be moved out of the path of the X-ray beam, limiting the need for additional shielding. Self-shape-reporting will be achieved using a flexible ultra-thin glass substrate with optical waveguides and Bragg gratings, processed by femtosecond laser point-by-point writing. The functionalized glass substrate allows precise measurement of strains, which can be used to calculate the shape. © 2022 The Author(s).