OPTICAL FIBER BIOSENSOR BASED ON SURFACE PLASMON RESONANCE FOR DNA HYBRIDIZATION DETECTION: MODELING, FABRICATION, AND CHARACTERIZATION

• Main Author: SITI AMINAH - NIM: 30212007 , NINA
• Format: Dissertations
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/23499
• Institution: Institut Teknologi Bandung

Biosensor based-on surface plasmon resonance (SPR) using polychromatic light coupling was developed to investigate the change in refractive index which occur as a result of chemical or biochemical processes. The study begins by studying the conventional SPR sensor using a prism to observe the reflectance spectrum at each variation of the angle of light. The thin film layers of gold deposited using a sputtering method to excite the surface plasmon mode (SP). At certain angles, resonance occurs, the tangential component of the wave vector comes together with real part wave vector surface plasmon waves are generated by evanescent that propagate along the boundary of metal-dielectric and decays exponentially in the normal direction of the boundary of metal-dielectric, thereby reducing the intensity of the reflectance and produce dip. The study is divided into two parts, namely, experiment and numerical simulation. Details of the experiments that include the fabrication and characterization of the sensor is given. Fabrication begins with the manufacture of tapered structures using homemade tapering rig. Consists of a stepper motor controlled by a PC connected in series, tapering rig pull one end of the optical fiber at a constant speed while heated to produce uniform-sized taper. The thin film layers of gold deposited using a sputtering method on taper structure obtained. UV-VIS characterization is done by using a light source polikromatis connected by fiber optic spectrometer and a Y-shaped branch. Characterization of the sensor is also done by immersion probe sensor into the test solution with different refractive indices. The experimental results for sensing taper structure in solution with a refractive index that is different is shown for the calculation of the sensitivity and resolution of the sensor. Numerical simulations were performed using the Finite Element Method (FEM). Finite Element Method has been established as one of the most powerful numerical methods and versatile and has been implemented in this dissertation to characterize, analyze and optimize optical biosensor. In the simulation, the complex dielectric constant of the metal is calculated using perturbation techniques. Formulation-field vector H for the TM mode is applied, and the complex propagation and attenuation constant of the surface plasmon mode is obtained using the finite element method for the optical waveguide with a structure consisting of a thin metal film bounded by two dielectric media. In this study, the sensor is used to determine whether there is a process of hybridization of DNA (deoxyribonucleic acid). DNA hybridization is bonding double strand DNA (dsDNA) between the two sets of single strand (ssDNA) are mutually complementary through base pairing N. Numerical simulations discussed two different architectures of optical biosensor without labeling. First, the biosensor fiber optics-based surface plasmon resonance (SPR) for the detection of DNA hybridization with the system architecture interferometer Mach-Zehnder (MZI) modeling optics by using the finite element method with the technique of perturbation to have easy form of computing is more efficient and can be used for the optical waveguide with the value of loss is low or medium. Sensing architecture with the principles of Mach-Zehnder interferometer based on a beam of light is split into two beams which then combined again the combination of results can be captured by the detector as the optical interference. The phase shift when the index of refraction vary from 1,456 (ssDNA) to 1.53 (dsDNA) have been observed. Based on the nature of the evanescent wave in the waveguide nanowires were investigated using FEM based on the formulation of full-field vector-H to detect the presence of DNA hybridization process found that the numerical methods do provide experimental sensitivity and good detection limits. The second simulation is done on the architecture of taper. Using modeling optics by using the finite element method and technique of perturbation same, by varying the radius of the core nanowires, can be proved that the field evanescent compounded by the reduced size of the radius of the core, so it can be proven that the sensitivity of the sensor with the structure of taper increases in taper section.