PHOTONIC SENSORS Photonic Crystal Based Biosensor for the Detection of Glucose Concentration in Urine Savarimuthu ROBINSON* and Nagaraj DHANLAKSMI Department of Electronics and Communication Engineering, Mount Zion College of Engineering and Technology, Pudukkottai, 622507, Tamil Nadu, India *Corresponding Author: Savarimuthu ROBINSON E-mail: [email protected] Abstract: Photonic sensing technology is a new and accurate measurement technology for bio-sensing applications. In this paper, a two-dimensional photonic crystal ring resonator based sensor is proposed and designed to detect the glucose concentration in urine over the range of 0 gm/dl-15 gm/dl. The proposed sensor is consisted of two inverted “L” waveguides and a ring resonator. If the glucose concentration in urine is varied, the refractive index of the urine is varied, which in turn the output response of sensor will be varied. By having the aforementioned principle, the glucose concentration in urine, glucose concentration in blood, albumin, urea, and bilirubin concentration in urine are predicted. The size of the proposed sensor is about 11.4 m×11.4 m, and the sensor can predict the result very accurately without any delay, hence, this attempt could be implemented for medical applications. Keywords: Biosensor; photonic crystal; refractive index; urine; glucose; urea Citation: Savarimuthu ROBINSON and Nagaraj DHANLAKSMI, “Photonic Crystal Based Biosensor for the Detection of Glucose Concentration in Urine,” Photonic Sensors, DOI: 10.1007/s13320-016-0347-3. 1. Introduction 40 mg/dl. High blood glucose level is known as “Hyperglycemia” and ranges from 270 mg/dl to After the invention of the optical sensor by Clark 360 mg/dl [2]. It indicates as diabetes mellitus, liver, and Lyons in 1962, optical sensing mechanisms and kidney related diseases [3–5]. receive considerable attention in the areas of According to the World Health Organization industrial process control, military, environmental (WHO), about 422 million people are affected by monitoring, medical diagnostics, etc. Glucose diabetes in the year of 2014 [6]. The global concentration is affected by the physical properties prevalence of diabetes among adults over 18 years of refractive index, specific gravity, surface tension, of age has risen from 4.7% in 1980 to 9% in 2015. and viscosity. Generally, glucose present in urine is Diabetes prevalence has been rising more rapidly in referred as “Glycosuria” [2] and normal range from middle- and low-income countries. Diabetes is fast 0 mg/dl to 15 mg/dl. If the level is increased from the gaining the status of a potential epidemic in India normal range, it means high glucose level in blood. with more than 62 million diabetic individuals Normal blood glucose level is between 165 mg/dl currently diagnosed with the disease. In 2000, India and 180 mg/dl. The level being too low is known as (31.7 million) topped the world with the highest “Hypoglycemia”, i.e. the range from less than number of people with diabetes mellitus followed by Received: 22 May 2016 / Revised: 5 September 2016 © The Author(s) 2016. This article is published with open access at Springerlink.com DOI: 10.1007/s13320-016-0347-3 Article type: Regular Photonic Sensors China (20.8 million) and the United States (1D), two dimensional (2D), and three dimensional (17.7 million) in the second and third place, (3D) PC. In this paper, we consider a 2DPC because respectively. The prevalence of diabetes is predicted it has a simple structure, small size, and high to double globally from 171 million in 2000 to 366 confinement of light and more convenient when million in 2030 with a maximum increase in India. It compared with 1D and 3D photonic crystals. PC is is predicted that by 2030 diabetes mellitus may providing an accurate sensing platform because of afflict up to 79.4 million individuals in India. Also the strong confinement of light inside the device [12, WHO noticed that diabetes is going to be the 7th 13]. Typically, PC is having PBG, which is entirely leading diseases in the world, of which diseases are broken by introducing either line defect or point hardening of the arteries, heart disease, stroke, defect. By breaking the defects, PC based optical kidney disease, blindness, infections and loss of toes, devices, such as filter [14, 15], directional coupler feet, (or) fingers caused by poor circulation, and [16], demultiplexer [17, 18], triplexer [19, 20], infection [7]. One-fifth of the world population is power splitter [21, 22], logic gates [23], switches [24, suffering from urine related problems [2]. 25], electro-optical modulators [26, 27], add-drop The conventional prediction method monitors filter [28, 29], and sensors [30-41], were reported. the glucose concentration in urine or blood. The In the literature, PC/PCRR based sensors were pinpricking method is an invasive method for the reported for bio sensing applications [30, 31], analysis of glucose concentration in blood. However, salinity sensor for different temperatures [32], it needs (5 mg/dl to 15 mg/dl) more blood samples chemical sensor [33], force/strain sensor [8]. Fluorescent glucose biosensor measures the applications [34, 35], pressure sensor [36], biosensor concentration of glucose in diabetic patients and in to detect the glucose concentration in urine [5, 37, small molecules dyes [9]. Continuous glucose 38], aqueous environment [39], breast cancer [40], monitoring method is used to measure the glucose cancer cell detection [41], pregnancy test, etc. In this concentration in blood by using the glucose sensor. paper, a photonic crystal based biosensor is designed, The disposable sensor is placed under the skin and sensing characteristics such as the Q factor, which is very painful [8]. Another method is using resonant wavelength, and normalized output power test strips. In this method, the strip color is changed are estimated for albumin, bilirubin, urea, and according to the concentration of glucose in urine. It glucose in urine and also glucose concentration in is based on air borne or finger borne contamination. blood. Rsoft FullWAVE and BandSOLVE simulator So, the result is inaccurate [10]. It is highly possible is employed to get band diagram and normalized to get the accurate result with in the desired time output power of the sensor. using the photonic crystals (PC) based sensor. The reminder of the paper is given as follows. In In 1987, Yablonovitch introduced PC [11]. The Section 2, the sensing principle is discussed. The photonic crystal is composed of periodic dielectric design of biosensor using 2DPC in square lattice is or metallo-dielectric nanostructures that have presented in Section 3. The obtained simulation alternatively low and high dielectric constant results are discussed in 4 Section. Finally, Section 5 materials (refractive index) to affect the propagation concludes the paper. of electromagnetic waves inside the structure. PCs 2. Biosensor design have a unique optical property called photonic band gap (PBG). Based on the variation of refractive The proposed PC based glucose sensor is used to index in one, two, and three directions, PCs are detect the glucose, albumin, bilirubin, and urea classified into three types namely one dimensional concentration in urine and blood. The biosensor is Savarimuthu ROBINSON et al.: Photonic Crystal Based Biosensor for the Detection of Glucose Concentration in Urine designed using 2DPC with circular rods in a square 1.2 lattice. PCs control the flow of light inside the 1.0 structure with the help of defects (point/line) which ) / a = can be employed for sensing application [42, 43]. 0.8 /2 a The 21×21 square lattice PC structure is considered for the biosensor design. The distance 0.6 between the two nearest rods is 540 nm which is 0.4 Frequency ( Frequency termed as a lattice constant, and it is denoted by “a”. 0.2 The radius of the rod is 100 nm. The refractive index of the Si rod is 3.46, and it is surrounded by air. The 0.0 design parameter of the proposed sensor is listed in X M (a) Table 1. 0.5 Table 1 Design parameters of the proposed biosensor. ) 0.4 Parameters Values / a Guided mode Configuration Rod in air = Rod shape Circular /2 0.3 a Lattice structure Cubic/square Lattice constant 0.540 µm 0.2 Radius of the rod 0.1 µm Refractive index of the rod 3.46 Dielectric constant of Si rod 11.97 ( Frequency 0.1 Figure 1(a) sketches the band diagram of the structure without any defects, which usually gives 0.1 0.2 0.3 0.4 0.5 Wavevector (2/a) the range of transverse electric/transverse magnetic (b) (TE/TM) PBG and propagation modes inside the Fig. 1 Band diagram for circular rods in 21×21 square lattice: (a) without any defects and (b) with line and point defects. periodic structure. There are two TM PBGs exist in The schematic representation of the proposed the structure which are indicated by blue color. As sensor is shown in Fig. 2. The proposed sensor is TE PBG is not present in the structure, the TM consisted of two inverted “L” waveguides and a ring polarization is considered for this simulation. The resonator. The inverted “L” waveguide is created by normalized frequency of the first reduced TM PBG introducing line defects, and the ring resonator is is observed from 0.435 a/ to 0.295 a/ whose designed by having both line/point defects. corresponding wavelength ranges from 1241 nm to Generally, to remove a row/column of rods is line 1830 nm, and the second PBG is from 0.754 a/ to defects whereas to remove or change structural 0.732 a/ whose corresponding wavelength spans parameters of a single rod is represented as point from 716 nm to 737 nm.