Hollow-Core Microstructured Optical Fiber Based Refractometer: Numerical Simulation and Experimental Studies.

In this paper, we numerically and experimentally propose a novel hollow-core microstructured optical fiber (HC-MOF) biosensor for refractive index determination. The sensing mechanism of the proposed sensor is based on photonic bandgap effect and the location of transmission maxima of the fiber, which is strongly depend on the liquid analyte RI filled in the fiber core. The proposed HC-MOF biosensor demonstrates the spectral sensitivity of 5636.3 nm/RIU with a RI detection range of 1.333 to 1.3385 for different ratios of plasma in blood serum in our experimental studies. The HC-MOF proposed here can detect similar liquid analytes with RI close to 1.33. The proposed sensor with a high sensitivity, ease of operation and the possibility of real-time sensing has a strong potential for detection of liquid analytes and biomolecules with possible applications in medicine, chemistry, and biology.

Detection of Blood Glucose With Hemoglobin Content Using Compact Photonic Crystal Fiber.

We have proposed Twin Elliptical Core Photonic Crystal Fiber (TEC-PCF) sensor for the detection of blood glucose level under the influence of hemoglobin components. The main featuring of the proposed biosensor is to detect the wide range of blood glucose content with enhanced sensitivity, by utilizing small length of the fiber. In order to achieve this, we have constructed asymmetric TEC-PCF where the elliptical core is filled by blood sample. The numerical sensing characteristics are evaluated using Finite Element Method (FEM). By varying hemoglobin concentrations as 120 g/L, 140 g/L and 160 g/L, we realize enhanced blood glucose sensing with detection range from 0 g/L to 100 g/L. The sensing performance of the proposed biosensor is studied through the coupling length and transmission power spectrum by calculation of effective index of the coupling mode. The obtained maximum wavelength sensitivity under the influence of 160 g/L hemoglobin content is 2.4 nm/(g/L) and 2.42 nm/(g/L) with fiber length of 0.245 mm and 0.215 mm for X and Y polarization, respectively. Further, limit of detection (LOD) is calculated under the influence of 160 g/L hemoglobin content is 0.375 mg/L and 0.372 mg/L for X and Y polarization, respectively. The proposed miniaturized sensing device can be integrated with microfluidic systems for the development of next-generation biosensor applications as point of- care and lab-on-a-chip.

Photonic Crystal Fiber-Based Reconfigurable Biosensor Using Phase Change Material.

A reconfigurable biosensor with different spectral sensitivities could provide new opportunities to increase the label-free selectivity and sensitivity for biomolecules. Here, we propose and numerically demonstrate a phase change chalcogenide material (Ge2 Sb2 Te5)-based photonic crystal fiber (PCF) sensor for tunable and enhanced refractive index sensing at near infrared (NIR) wavelengths. In order to achieve this, we integrate a thin hybrid sensing layer of Au/Ge2 Sb2 Te5 with D-shaped PCF. By switching the structural phase of Ge2 Sb2 Te5 from amorphous to crystalline, we realize tunable and enhanced refractive index sensing with a large figure of merit (FOM) for the sensing range from 1.35 to 1.40, which covers most known analytes such as proteins, cancer cells, glucose and viruses or DNA/RNA. The obtained average bulk refractive index sensitivity is 17,600 nm/RIU and 8,000 nm/RIU for crystalline and amorphous phase, respectively. The observed large tunable differential response of the proposed sensor offers a promising opportunity to design an assay for the selective detection of higher and lower molecular weight biomolecules through future artificial intelligence-based sensing.

Ultra-wetting graphene-based PES ultrafiltration membrane - A novel approach for successful oil-water separation.

Oil pollution in water and separation of oil from water are receiving much attention in recent years due to the growing environmental concerns. Membrane technology is one of the emerging solutions for oil-water separation. However, there is a limitation in using polymeric membrane for oil water separation due to its surface properties (wetting behaviour), thermal and mechanical properties. Here, we have shown a simple method to increase the hydrophilicity of the polyethersulfone (PES) hollow fibre ultrafiltration (UF) membrane by using carboxyl, hydroxyl and amine modified graphene attached poly acrylonitrile-co-maleimide (G-PANCMI). The prepared membranes were characterized for its morphology, water and oil contact angle, liquid entry pressure of oil (LEPoil), water permeability and finally subjected to a continuous 8 h filtration test of oil emulsion in water. The experimental data indicates that the G-PANCMI play an important role in enhancing the hydrophilicity, permeability and selectivity of the PES membrane. The water contact angle (CAw) of the PES membrane is reduced from 63.7 ± 3.8° to 22.6 ± 2.5° which is 64.5% reduction while, the oil contact angle was increased from 43.6 ± 3.5° to 112.5 ± 3.2° which is 158% higher compared to that of the PES membrane. Similarly, the LEPoil increased 350% from 50 ± 10 kPa of the control PES membrane to 175 ± 25 kPa of PES-G-PANCMI membrane. More importantly, the water permeability increased by 43% with >99% selectivity. Based on our findings we believe that the development of PES-G-PANCMI membrane will open up a solution for successful oil-water separation.

Nanofiber based triple layer hydro-philic/-phobic membrane--a solution for pore wetting in membrane distillation.

The innovative design and synthesis of nanofiber based hydro-philic/phobic membranes with a thin hydro-phobic nanofiber layer on the top and a thin hydrophilic nanofiber layer on the bottom of the conventional casted micro-porous layer which opens up a solution for membrane pore wetting and improves the pure water flux in membrane distillation.

Self-cleaning Metal Organic Framework (MOF) based ultra filtration membranes--a solution to bio-fouling in membrane separation processes.

Bio-fouling is a serious problem in many membrane-based separation processes for water and wastewater treatment. Current state of the art methods to overcome this are to modify the membranes with either hydrophilic additives or with an antibacterial compound. In this study, we propose and practise a novel concept to prevent bio-fouling by developing a killing and self-cleaning membrane surface incorporating antibacterial silver nanoparticles and highly hydrophilic negatively charged carboxylic and amine functional groups. The innovative surface chemistry helps to reduce the contact angle of the novel membrane by at least a 48% and increase the pure water flux by 39.4% compared to the control membrane. The flux drop for the novel membrane is also lower (16.3% of the initial flux) than the control membrane (55.3% of the initial flux) during the long term experiments with protein solution. Moreover, the novel membrane continues to exhibit inhibition to microbes even after 1320 min of protein filtration. Synthesis of self-cleaning ultrafiltration membrane with long lasting properties opens up a viable solution for bio-fouling in ultrafiltration application for wastewater purification.