Design and Performance Analysis of Simple PCF Based Sensor with High Sensitivity for Sensing the Presence of Bacteria - Pseudomonas aeruginosa

Research Article

Annals Thyroid Res. 2022; 8(1): 360-367.

Design and Performance Analysis of Simple PCF Based Sensor with High Sensitivity for Sensing the Presence of Bacteria - Pseudomonas aeruginosa

Bin Murshed Leon MJ1*, Disha AS2 and Rahman Hemal MS3

¹Department of Electronics and Telecommunication Engineering, Chittagong University of Engineering and Technology, Chattogram, Bangladesh

²Environmental Science Discipline, Khulna University, Khulna, Bangladesh

³Department of Pharmacy, Southeast University, Dhaka, Bangladesh

*Corresponding author: Md. Jayed Bin Murshed Leon, Department of Electronics and Telecommunication Engineering, Chittagong University of Engineering and Technology, Chattogram, Bangladesh

Received: December 31, 2021; Accepted: January 27, 2022; Published: February 03, 2022

Abstract

Pseudomonas aeruginosa is a nosocomial infectious disease with high mortality rates due to its innate and acquired resistance to a wide variety of antibiotics. As a result, rapid identification of the pathogenic bacterium with high specificity and sensitivity is essential in protecting against disease. This paper presents a PCF-based biosensor with promising performance characteristics for detecting the existence of Pseudomonas bacteria. A simple structure of the proposed sensor most importantly the core regions may reduce the fabrication complexity. The proposed structure is numerically analyzed using the full finite element model and the optical parameters are investigated using Perfectly Matched Layer (PML). The designed PCFs have been put to the test for detecting the existence of Pseudomonas aeruginosa bacteria. The numerical investigation has done in a range of wavelengths from 0.9μm to 1.1μm and for the RI value of 1.33 to 1.37. Increasing the diameter of the air holes in the microstructure core and adjusting the thickness of the PML improve relative sensitivity considerably. The proposed sensor test is carried out on various PML radius values and hole’s diameter variations in the core section. The proposed sensor provides maximum sensitivity is 44.06% and minimal confinement loss 0.008410 (dB/m) at a fixed wavelength 1μm.

Keywords: Photonic crystal fiber; Bacteria Sensor; Finite Element Method; Perfectly Matched Layer; Sensitivity; Confinement loss

Introduction

Pseudomonas aeruginosa is a Pseudomonadaceae bacterium that is gram-negative, asporogenous, and mono flagellated (a member of the Gammaproteobacteria). It’s a rod-shaped object that’s about (1-5) μm long and (0.5-1.0) μm wide [1]. It has a pearlescent appearance and smells like grapes or tortillas. Pseudomonas aeruginosa is an important respirator that requires oxygen for optimum metabolism, though it can also breathe anaerobically using other electron acceptors. Pseudomonas aeruginosa thrives in temperatures ranging from 25oC to 37oC. Pseudomonas aeruginosa is a ubiquitous bacterium that can thrive in a wide range of environments, including distilled water [2]. Pseudomonads aeruginosa is primarily found in soil, seawater, and freshwater. They can also colonize plants and livestock, and they’re common in homes and hospitals [3]. They have a large effect on biodiversity, agriculture, and trade due to their widespread distribution in both terrestrial and aquatic ecosystems. They are also responsible for food spoilage and degradation of petroleum products in the environment. Pseudomonas aeruginosa is one of the most common plant pathogens in agriculture [4]. It not only responsible for diseases in plants and animals but also in humans, causing serious infections in immunocompromised. Patients with cystic fibrosis, burn wounds, organ transplants, acute leukaemia, and intravenous drug abuse are all at risk for Pseudomonas infection [5]. It is a common cause of nosocomial infections in hospitals, particularly in intensive-care units (ICU). In most hospitals, it is responsible for 20% of all infections. Patients who have been in the hospital for a long time are often infected with this organism and are at a high risk of infection. The most serious infections include endophthalmitis, malignant external otitis, meningitis, endocarditis, septicaemia and pneumonia [6]. P. aeruginosa infections are not only normal, but they also have a high mortality and morbidity rate as compared to other bacterial pathogens. The nature of the patient’s underlying condition determines the likelihood of recovery from pseudomonas infection. Furthermore, treatment of this infection is being rendered increasingly problematic due to the emergence and spread of resistance mutant among this pseudomonas group [5]. They are often immune to several antibiotics and have been dubbed “superbugs” due to their immense capacity to breed resistance. It suggests that due to low outer membrane permeability and adaptive mechanisms, this species is less susceptible to most antibiotics and is more likely to develop clinical resistance [7]. This resistance mechanism has complicated treatment options for Pseudomonas aeruginosa infections, which have become a severe and deadly problem in the United States, causing 51,000 healthcare infections per year [8]. Given the possible seriousness of these infections and the difficulty in determining the best treatment, detecting, and identifying Pseudomonas aeruginosa is a top priority.

PCF is an optical fiber with a photonic crystal cladding that surrounds the cable’s core. A photonic crystal is a low-loss periodic dielectric medium consisting of a regular pattern of microscopic air holes running the length of the fiber. Fiber optic cables have a constant refractive index difference in the core and a constant refractive index difference in the cladding. Light is concentrated in the core of PCF which provides a much stronger waveguide for photons than normal fiber optics. PCF is made of polymers rather than glass, resulting in a more durable fiber that is therefore easier and less expensive to produce. Photonic crystal fiber is also known as micro-structured or holey fiber. Photonic bandgap (PBG) structures with hollow cores may be more advantageous for sensing applications [9]. Light is directed in the hollow region of an optical fiber with a hollow core [10]. As a result, only a small amount of light can reach the solid fiber material (typically a glass). These fibers are known as photonic bandgap fibers. The PCF guides light by inserting and limiting air holes along the length of the fibers at regular intervals. The size of holes in the core and cladding can be adjusted to control light propagation. Because of its ability to detect light in hollow bodies, it has low blockage loss and enhanced light penetration, resulting in increased fiber sensitivity [11]. PCF-based sensors are also capable of detecting oil or fuel toxicity in addition to sensing applications [12].

Several studies on the performance of optical sensors based on PCF have been published. Photonic crystal fibers are used in spectroscopy, metrology, bioengineering, imaging, telecommunication, industrial machining, and military technology. PCF is used in a variety of applications, including gas detection [13], chemical detection [14], pressure detection [15], bio-medical and temperature sensing, and so on. The authors proposed a liquid (water) sensing sensor and designed the core section with holes of different diameters. The overall sensitivity of their sensor is about 49.13%, and it’s become clear how the sensitivity increases as the diameter of the hole changes [16]. In [17], the authors suggested a basic circular lattice PCF made up of two air hole rings and a thin layer of gold on the outside of the PCF structure. The proposed structure should have the highest sensitivity possible, including amplitude sensitivity and sensor resolution. The author [18] proposed a gold-coated dual-core sensor with hexagonally arranged circular air holes based on the SPR-PCF sensor. The plasmonic material in this design is gold, a chemically inactive and stable element. The impact of changing gold layer thickness, pitch, and analyte layer thickness on confinement loss and amplitude sensitivity is described in this paper. The maximum sensitivity of the proposed structure is 10,700 nm/RIU for analyte RI changing from 1.39 to 1.40. The authors [19] modeled a structure to detect liquid analytes, but their proposed sensor can detect water, 10% glucose solution, and mucosa at the same time with corresponding sensitivity and birefringence using the same structure. Some authors [20] have proposed spiral type photonic crystal fiber (S-PCG) as a gas sensor. They proposed a porous PCF with a core region with a cluster of circular air holes and cladding with a spiral shape that also includes air holes. Between the wider wavelength ranges of 1 to 1.8m, the proposed S-PCF exhibited maximum relative sensitivity of about 55%.

Recently [21], authors designed vertical and horizontal PCF structures for sensing sulfur dioxide gas, and then formed the elliptical core to achieve high relative sensitivity and low confinement loss at the same time. They compared and contrasted the efficiency of H-PCF and VPCF, as well as how variations in PML thickness affect the sensitivity value of the proposed structure. The V-PCF sensor has the highest sensitivity of 59.344% while the HPCF sensor has a sensitivity of 58.34%.

Sensor systems for the detection of pathogenic bacteria have reawakened interest in recent years, especially in the fields of food safety, medical diagnosis, and biological warfare. This is due to an increase in the number of bacteria-related illnesses over the world. Authors [22] tested the sensor’s performance by monitoring the adhesion of Escherichia coli K12 cells to the sensor surface. The sensor’s output was evaluated by tracking the adhesion of Escherichia coli K12 cells to the sensor’s surface. A bacterial solution was made by suspending and washing a single Escherichia coli K12 colony from an agar plate in a 10-mL phosphate-buffered saline solution (PBS) resulting in a concentration of 3×107 cells/mL They have calculated the peak angle sensitivity of 1.65 ×10-6 (deg/cell)/mm². Obtained average single-cell sensitivities of 1.3×10-6 and 1.65× 10-6 (deg/cell)/ mm² for TE and TM modes respectively.

For the detection of Pseudomonas bacteria, a highly sensitive SPR biosensor based on silver (Ag), barium titanate (BaTiO3), graphene, and an affinity layer is proposed [23]. The proposed structure has been analyzed by using the angular modulation method in this paper. They investigated the reflectivity of a p-polarized incident light wave using the Fresnel multilayer reflection theory and the transfer ma- Trix process. They analyzed the impact of silver and barium titanate layer thickness on minimum reflectivity at a fixed wavelength of 633nm. The adsorption of Pseudomonas bacteria on the surface of the graphene layer with the guidance of the affinity layer is the detection mechanism. The sensing medium in their proposed SPR structure is water, which has a refractive index of 1.33. Maximum sensitivity, quality parameter and detection accuracy for this proposed structure are obtained as 220 degree/RIU, 101.38 RIU-1 and 7.09 respectively for change in the refractive index of the sensing medium from n = 1.33 to 1.40. The authors [24] proposed a biosensor that detects changes in refractive index near the sensor surface using the attenuated total reflection process. When these findings are compared to those of a traditional gold layer surface plasmon resonance biosensor, it is clear that adding the graphene layer improves the overall performance of the proposed biosensor. In comparison to traditional SPR biosensors, their proposed SPR biosensor with graphene layer has low loss and maximum surface mode excitation. The dip in reflectance transitions towards a higher value of incident angle as the cover refractive index increases from nc = 1.33 to nc = 1.40. This is a bacterial symbol, and the angle shift is completely dependent on the concentration and mobility of bacteria. Proposed SPR biosensor with graphene layer provides Sensitivity (Degree/RIU) value is 33.98% when Conventional SPR biosensor without graphene layer shows 30.85%. A zinc oxide (ZnO), gold (Au), and graphene-based SPR biosensor for the identification of pseudomonas and pseudomonaslike bacteria suggested by the authors [25]. The performance of the proposed SPR biosensor is focused on the angular interrogation method and theoretical analysis of sensitivity, detection accuracy, quality parameter, and electric field intensity enhancement factor (EFIEF). They looked into the efficiency of a ZnO, gold and graphenebased hybrid SPR biosensor structure. BK-7 glass prism, ZnO, Au, graphene, and affinity layer are all part of their proposed four-layer planar structure. They’ve also examined at how a graphene layer affects the sensitivity of a proposed SPR biosensor for pseudomonas detection. It is also clear from their research that increasing the affinity layer refractive index reduces sensitivity, detection precision, and efficiency parameter over time. The proposed biosensor based on ZnO has better performance parameters than other traditional biosensors, and increasing the number of graphene layers reduces sensitivity, as described in this paper. The proposed biosensor has a greater sensitivity of 187.43 deg/RIU, the detection accuracy of 2.05deg-1, quality parameter of 29.33 RIU-1 and enhanced EFIEF for the detection of pseudomonas-like bacteria when compared to other identified conventional SPR biosensors. Very recent time [26] a surface plasmon resonance (SPR) biosensor based on photonic crystal fiber (PCF) has been proposed to detect the presence of Pseudomonas bacteria with attractive performance characteristics. To overcome the limitations of the prism-based sensor, this paper uses a wavelength interrogation (WI) and amplitude interrogation (AI) approach. The proposed SPR sensor, which uses a single air hole ring to design the sensor. The pitch, or the distance between the centers of two contiguous air holes, is p = 1.5 m when all of the air holes inside the ring are spaced at 30. Two separate air holes are used in this ring, with the larger air holes having a diameter of D = 0.2×p m. The smaller air holes at 60, 120, 240, and 300 have a diameter of D1 = 0.75×D m, which helps to create a path that allows more light to pass through the metal interface, creating a more evanescent field. In this structure, water with a RI of 1.33 is used as a sensing medium. 20,000 nm/RIU and 1380 RIU-1 are the highest wavelength and amplitude sensitivity, respectively. The sensor has an excellent spectral resolution, with a maximum value of 5.26×10-6 RIU, allowing it to detect very minor changes in analyte refractive index (RI) in the range of 1.33 to 1.42. The author [36] presents a hollow core Photonic Crystal Fiber (HCPCF) to detect blood components. To detect each blood component, that component needs to place into the core hole and the amount of blood sample depends on the size of the core. Also, six rectangular holes (R1-R6) are considered surrounding the core where they put air to guide light within the analyte Their proposed HCPCF sensor provides high sensing performance and the relative sensitivity is achieved approximately 89.14% for water, 90.48% for plasma, 91.25% for white blood cells (WBCs), 92.41% for hemoglobin (HB), 93.50% for red blood cells (RBCs) at frequency 2 THz for the ideal design. This sensor also offers a very negligible amount of light confinement loss (CL) and a high effective area (EA). The CL is found around 1.3×10-13 cm-1, 9.1×10-14 cm-1, 7.52×10-14 cm-1, 4.98×10, cm-1, 3.11×10-14 cm-1 and the EA is noticed almost 2.2×105 μm², 2.18×105 μm², 2.16×105 μm², 2.14×105 μm², 2.12×105 μm² for water, plasma, WBCs, HB, RBCs, respectively, at frequency 2 THz.

A dual-core liquid-filled photonic crystal fiber coupler (PCFC) with rectangular (RPCFC) and hexagonal (HPCFC) geometry are presented [37] from the 1200 to 1800 nm wavelength range in the proposed design. In the proposed design, four air-holes rings where each air-hole diameter, d=0.6 μm, and lattice pitch Λ = 2.3 μm is chosen at the 1.55 μm wavelength, RPCFC shows 0.000318, 0.000358, and 0.000379 m coupling lengths for the water, chloroform, and benzene-filled dual-core, respectively. Additionally, the confinement loss of 1.57×10-7, 1.22×10-7, and 1.05×10-7 dB/km are achieved through RPCFC.

PCF-based chemical sensor model is suggested [38] where Zeonex is used as the fiber material and this sensor performance is analyzed in the terahertz regime. The reported sensor model provides enhanced sensitivity (94.4%) along with tiny confinement loss (1.71 × 10-14 cm-1) at a frequency of 1.8 THz. Besides, the fabrication of this model is also probable by exercising subsisting fabrication methods. The hollow-core PCF is chosen for its numerous advantages for instance hollow-core fiber offers lower effective material loss (EML) and the fabrication of this proposed PCF model is possible by using existing fabrication methods.

Prism coupled an SPR-based sensor that operates on the concept of angular interrogation. Prism coupled sensors have certain disadvantages, which are overcome by traditional OF-based sensors. But their sensitivity is not very high and they are also limited to their design parameters. Furthermore, remote sensing applications are not possible with the prism-based SPR sensing system. If an optical fiber is used instead of a prism, these limitations can be resolved. The optical fiber also has the benefit of allowing the SPR probe to be miniaturized, which is beneficial for samples. In this regard, PCF-based sensors have a wide range of design parameters, such as variable index profiles, air hole diameters, number of air holes, pitch, plasmonic material thickness, plasmonic material location, and so on. The wavelength interrogation (WI) and amplitude interrogation (AI) methods are used in the PCF based sensor. Although they are limited to fabrication complexity but show better performances. That’s why PCF based sensors are nowadays being popular.

In this research, a PCF structure with a hexagonal arrangement and circular air holes designed. The proposed model has been demonstrated for sensing Pseudomonas aeruginosa bacteria with the goal of achieving higher sensitivity and minimal confinement loss at the same time. The light will be confined in the range of wavelength from 0.9 μm to 1.1 μm to detect the bacteria by the sensor. When light is well confined in the core area, the best result is obtained, and performance is measured. Variations in the diameter of the core region’s hole as well as the variations in PML thickness and how they influence the overall output of the suggested sensor are discussed in detail here

Proposed Structure

A PCF structure with a hexagonal arrangement of circular air holes in the cladding region has been suggested. The suggested PCF shape is hexagonal, rather than decagonal, square, or octagonal since the hexagon cell is decorative and can fill the entire region without gaps. The liquid in the core hole is allowed, according to research articles [27] since the refractive index allows incident light to pass directly through analytes.

Figure 1 shows a cross-sectional view of our proposed structure. The most important thing to note when designing a PCF-based sensor is to design the core section properly since light is confined there. Light confinement and design or fabrication complexity are often considered even before designing a new structure.