Advances in Optofluidics

Optofluidics a niche research field that integrates optics with microfluidics. It started with elegant demonstrations of the passive interaction of light and liquid media such as liquid waveguides and liquid tunable lenses. Recently, the optofluidics continues the advance in liquid-based optical devices/systems. In addition, it has expanded rapidly into many other fields that involve lightwave (or photon) and liquid media. This Special Issue invites review articles (only review articles) that update the latest progress of the optofluidics in various aspects, such as new functional devices, new integrated systems, new fabrication techniques, new applications, etc. It covers, but is not limited to, topics such as micro-optics in liquid media, optofluidic sensors, integrated micro-optical systems, displays, optofluidics-on-fibers, optofluidic manipulation, energy and environmental applciations, and so on

Multi-channel SPR biosensor based on PCF for multi-analyte sensing applications

This paper presents a theoretical investigation of a novel holey fiber (Photonic Crystal Fiber (PCF)) multi-channel biosensor based on surface plasmon resonance (SPR). The large gold coated micro fluidic channels and elliptical air hole design of our proposed biosensor aided by a high refractive index over layer in two channels enables operation in two modes; multi analyte sensing and self-referencing mode. Loss spectra, dispersion and detection capability of our proposed biosensor for the two fundamental modes (HE x 11 and HE y 11 ) have been elucidated using a Finite Element Method (FEM) and Perfectly Matching Layers (PML)

Biological Lasers for Biomedical Applications

A biolaser utilizes biological materials as part of its gain medium and/or part of its cavity. It can also be a micro- or nanosized laser embedded/integrated within biological materials. The biolaser employs lasing emission rather than regular fluorescence as the sensing signal and therefore has a number of unique advantages that can be explored for broad applications in biosensing, labeling, tracking, contrast agent development, and bioimaging. This article reports on the progress in biolasers with focus on the work done in the past five years. In the end, the possible future directions of the biolaser are discussed.Biolasers and their applications in biology and biomedicine are reviewed in this progress report. The biolaser employs lasing emission rather than regular fluorescence as the sensing signal and therefore has a number of unique advantages that can be explored for broad applications in biosensing, labeling, tracking, contrast agent development, and bioimaging.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/151258/1/adom201900377.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/151258/2/adom201900377_am.pd

Plasmonic microstructured optical fibres: an efficient platform towards biosensing

Detecting life-threatening diseases is a major challenge in biomedicine, as it requires pathogen identication on the molecular level. One promising detection strategy relies on attaching molecular probes to nanoparticles (NPs), which support localised surface plasmon resonance (LSPR). Probe-functionalised NPs can then detect molecular DNA-binding events via a macroscopic change in their optical response. Until now, NP-sensing schemes have been primarily implemented using planar substrates, requiring complex launching techniques and cost-intensive microscopy. An alternative approach adopted in this work involves inltrating optical bres with NPs allowing LSPR excitation and spectral multiplexing within one device. The principle idea relies on probing deposited plasmonic NPs by propagating optical fibre modes, leading to hybrid plasmonic-photonic fibres for biosensing. An important class of innovative bres exploited in this work are microstructured optical bres (MOFs) containing longitudinally invariant microstructures. These structures enable unprecedented adjustment of light matter interaction resulting in a high degree of sensitivity and an optofluidic environment ideally suited for biochemical application. In this thesis optofluidic channels are integrated in direct proximity to the light guiding core, boosting the light-analyte interaction length by orders of magnitude. This concept thus represents a multiscale approach, fundamentally connecting the microscopic level via LSPR-mediated sensing with the macroscopic world using MOFs leading to a novel and unexplored sensor platform. This study shows that combining plasmonic-bre waveguides with microuidics yields a highly integrated, reusable, optouidic interface for efcient refractive index sensing with outlook for DNA diagnostics. This unique combination is extremely attractive from both device and clinical point of view, as the flexible handling of optical fibres principally enables in-vivo application

An Ultra-Sensitive Visible-IR Range Fiber Based Plasmonic Refractive Index Sensor

Photonic crystal fiber (PCF)-based plasmonic sensors have gained considerable attention because of their highly sensitive performance and broad range of sensing regimes. In this work, a relatively simple ultra-sensitive PCF-based surface plasmon resonance (SPR) sensor has been proposed for detecting different analyte refractive indices (RIs) ranging from 1.33 to 1.43 over a wide range of wavelength spectrum spanning 0.55 $\mu$m to 3.50 $\mu$m. The comprehensive finite-element simulations indicate that it is possible to achieve remarkable sensing performances such as wavelength sensitivity (WS) and figure of merit (FOM) as high as 123,000 nm/RIU and 683 RIU$^{-1}$, respectively, and extremely low values of wavelength resolution (WR) of 8.13 x 10$^{-8}$ RIU. In addition, a novel artificial neural network (ANN) model is proposed to be integrated into the practical setup in order to accurately predict the RIs by carefully examining the simulation data. The mean square error (MSE) and accuracy ($R^2$) values for the ANN model are found about 0.0097 and 0.9987, respectively, indicating the high prediction capability of the proposed ANN model. Due to its exceptional sensitivity and precise detection capabilities, the proposed device has the potential to serve as a viable option for sensing analyte refractive index (RI). Additionally, the sensor could be utilized for identifying cancerous cells and detecting urinary tract infections in humans

Silicon-Based Integrated Label-Free Optofluidic Biosensors: Latest Advances and Roadmap

By virtue of the well-developed micro- and nanofabrication technologies and rapidly progressing surface functionalization strategies, silicon-based devices have been widely recognized as a highly promising platform for the next-generation lab-on-a-chip bioanalytical systems with a great potential for point-of-care medical diagnostics. Herein, an overview of the latest advances in silicon-based integrated optofluidic label-free biosensing technologies relying on the efficient interactions between the evanescent light field at the functionalized surface and specifically bound analytes is presented. State-of-the-art technologies demonstrating label-free evanescent wave-based biomarker detection mainly encompass three device configurations, including on-chip waveguide-based interferometers, microring resonators, and photonic-crystal-based cavities. Moreover, up-to-date strategies for elevating the sensitivities and also simplifying the sensing processes are discussed. Emerging laboratory prototypes with advanced integration and packaging schemes incorporating automatic microfluidic components or on-chip optoelectronic devices lead to one significant step forward in real applications of decentralized diagnostics. Besides, particular attention is paid to currently commercialized label-free optical bioanalytical models on the market. Finally, the prospects are elaborated with several research routes toward chip-scale, low-cost, highly sensitive, multi-functional, and user-friendly bioanalytical systems benefiting to global healthcare. © 2020 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei

Direct observation of modal hybridization in nanofluidic fiber [Invited]

Hybrid-material optical fibers enhance the capabilities of fiber-optics technologies, extending current functionalities to several emerging application areas. Such platforms rely on the integration of novel materials into the fiber core or cladding, thereby supporting hybrid modes with new characteristics. Here we present experiments that reveal hybrid mode interactions within a doped-core silica fiber containing a central high-index nanofluidic channel. Compared with a standard liquid-filled capillary, calculations predict modes with unique properties emerging as a result of the doped core/cladding interface, possessing a high power fraction inside and outside the nanofluidic channel. Our experiments directly reveal the beating pattern in the fluorescent liquid resulting from the excitation of the first two linearly polarized hybrid modes in this system, being in excellent agreement with theoretical predictions. The efficient excitation and beat of such modes in such an off-resonance situation distinguishes our device from regular directional mode couplers and can benefit applications that demand strong coupling between fundamentaland higher-order- modes, e.g. intermodal third-harmonic generation, bidirectional coupling, and nanofluidic sensing

A Highly Sensitive SPR Refractive Index Sensor Based on Microfluidic Channel Assisted with Graphene-Ag Composite Nanowire

A highly sensitive refractive index (RI) sensor based on a microfluidic channel (MFC) incorporated in a single-mode fiber (SMF), filled with Ag-graphene composite nanowire is presented and analyzed here. The sensing performance and the coupling properties of designed sensor are numerically analyzed by using a full vectorial finite element method (FEM) incorporating amplitude and wavelength interrogation techniques in the detection range varied from ${n_a}$ = 1.330-1.350. The maximum wavelength and amplitude sensitivity are obtained of 13700 nm/RIU and 1026 RIU-1, respectively. Here, the Ag-graphene composite nanowire can not only solve the problem of oxidation but also enhances the sensitivity of the sensor. In addition of high sensitivity, it also provides better performance than other sensing devices based on similar technologies such as Ag nanowire-filled sensors. Moreover, the influences of polishing depth (D), nanowire radius (rn), graphene layer (Lg) and channel size (s) on the designed sensor, are also thoroughly investigated here. The present work can provide a base for designing a real-time, highly sensitivity, remote sensing, and distributed SPR based RI sensor

Recent Progress in Optical Sensors for Biomedical Diagnostics

In recent years, several types of optical sensors have been probed for their aptitude in healthcare biosensing, making their applications in biomedical diagnostics a rapidly evolving subject. Optical sensors show versatility amongst different receptor types and even permit the integration of different detection mechanisms. Such conjugated sensing platforms facilitate the exploitation of their neoteric synergistic characteristics for sensor fabrication. This paper covers nearly 250 research articles since 2016 representing the emerging interest in rapid, reproducible and ultrasensitive assays in clinical analysis. Therefore, we present an elaborate review of biomedical diagnostics with the help of optical sensors working on varied principles such as surface plasmon resonance, localised surface plasmon resonance, evanescent wave fluorescence, bioluminescence and several others. These sensors are capable of investigating toxins, proteins, pathogens, disease biomarkers and whole cells in varied sensing media ranging from water to buffer to more complex environments such as serum, blood or urine. Hence, the recent trends discussed in this review hold enormous potential for the widespread use of optical sensors in early-stage disease prediction and point-of-care testing devices.DFG, 428780268, Biomimetische Rezeptoren auf NanoMIP-Basis zur Virenerkennung und -entfernung mittels integrierter Ansätz