High sensitivity detection of SARS-CoV-2 by an optofluidic hollow eccentric core fiber

Anti-resonant hollow core fiber with excellent bending resistance in the visible spectral range

The development of wideband guided hollow-core anti-resonant fiber (HC-ARF) that covers the sensitive range of the human eye's visible spectrum is progressing rapidly. However, achieving low-loss wideband transmission with a small bending radius remains a challenging issue to be addressed. In light of this, we propose a novel, to our knowledge, HC-ARF with a nested double-semi-elliptical cladding structure in the visible spectral region. By employing finite element method simulations, we investigate the confinement loss, bending loss, and single-mode performance of this fiber design. The result shows that the confinement loss of this new fiber exhibits below 10-5 dB·m-1 across almost the entire visible band range, with a minimum loss of 1.55 × 10-7 dB·m-1 achieved for λ = 650 nm. Furthermore, this fiber demonstrates excellent resistance to bending and can maintain an ultra-low bending loss as low as 3 × 10-7 dB·m-1 even under extreme bending conditions with a radius of only 3 cm. Notably, its 3-dB bending radius reaches just 3.5 cm for λ = 532 nm. Additionally, it exhibits outstanding single-mode conductivity under various bending scenarios and achieves a high extinction ratio of up to 104 for higher-order modes after parameter optimization for specific wavelengths.

Hierarchical Nanobiosensors at the End of the SARS-CoV-2 Pandemic

Nanostructures have played a key role in the development of different techniques to attack severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Some applications include masks, vaccines, and biosensors. The latter are of great interest for detecting diseases since some of their features allowed us to find specific markers in secretion samples such as saliva, blood, and even tears. Herein, we highlight how hierarchical nanoparticles integrated into two or more low-dimensional materials present outstanding advantages that are attractive for photonic biosensing using their nanoscale functions. The potential of nanohybrids with their superlative mechanical characteristics together with their optical and optoelectronic properties is discussed. The progress in the scientific research focused on using nanoparticles for biosensing a variety of viruses has become a medical milestone in recent years, and has laid the groundwork for future disease treatments. This perspective analyzes the crucial information about the use of hierarchical nanostructures in biosensing for the prevention, treatment, and mitigation of SARS-CoV-2 effects.

Optical Biosensors for the Diagnosis of COVID-19 and Other Viruses-A Review

The sudden outbreak of the COVID-19 pandemic led to a huge concern globally because of the astounding increase in mortality rates worldwide. The medical imaging computed tomography technique, whole-genome sequencing, and electron microscopy are the methods generally used for the screening and identification of the SARS-CoV-2 virus. The main aim of this review is to emphasize the capabilities of various optical techniques to facilitate not only the timely and effective diagnosis of the virus but also to apply its potential toward therapy in the field of virology. This review paper categorizes the potential optical biosensors into the three main categories, spectroscopic-, nanomaterial-, and interferometry-based approaches, used for detecting various types of viruses, including SARS-CoV-2. Various classifications of spectroscopic techniques such as Raman spectroscopy, near-infrared spectroscopy, and fluorescence spectroscopy are discussed in the first part. The second aspect highlights advances related to nanomaterial-based optical biosensors, while the third part describes various optical interferometric biosensors used for the detection of viruses. The tremendous progress made by lab-on-a-chip technology in conjunction with smartphones for improving the point-of-care and portability features of the optical biosensors is also discussed. Finally, the review discusses the emergence of artificial intelligence and its applications in the field of bio-photonics and medical imaging for the diagnosis of COVID-19. The review concludes by providing insights into the future perspectives of optical techniques in the effective diagnosis of viruses.

Optical Fiber Fabry-Pérot Microfluidic Sensor Based on Capillary Fiber and Side Illumination Method

In this paper, an optical fiber Fabry-Pérot (FP) microfluidic sensor based on the capillary fiber (CF) and side illumination method is designed. The hybrid FP cavity (HFP) is naturally formed by the inner air hole and silica wall of CF which is side illuminated by another single mode fiber (SMF). The CF acts as a naturally microfluidic channel, which can be served as a potential microfluidic solution concentration sensor. Moreover, the FP cavity formed by silica wall is insensitive to ambient solution refractive index but sensitive to the temperature. Thus, the HFP sensor can simultaneously measure microfluidic refractive index (RI) and temperature by cross-sensitivity matrix method. Three sensors with different inner air hole diameters were selected to fabricate and characterize the sensing performance. The interference spectra corresponding to each cavity length can be separated from each amplitude peak in the FFT spectra with a proper bandpass filter. Experimental results indicate that the proposed sensor with excellent sensing performance of temperature compensation is low-cost and easy to build, which is suitable for in situ monitoring and high-precision sensing of drug concentration and the optical constants of micro-specimens in the biomedical and biochemical fields.