| Label-free optical biosensors have a wide range of applications from biomedical research to bio-defense monitoring of known or potential bioterrorist threats. But currently, there are few commercial real-time portable bio-agent detection devices available. In this thesis a potential of bio-agent detection method, reflectometric interference spectroscopy (RIfS), for a compact label-free biosensor was investigated. A model to estimate sensitive layer thickness variation on the sensor chip was developed.;The prototype using Altera Cyclone III FPGA chip as the main processor core was built in the design. The bio-agent detection device consists of four main parts, which include a dual-LED sensor module, a Field-Programmable Gate Array (FPGA) board, an interface circuit board, and a power supplier. The LEDs' signal is converted into digital data by interface board and processed by the FPGA board. The measurement results are shown by the interface board. The device is powered by a nine-volt battery (PP3 battery), which enables portability of the device. Meanwhile, the wireless communication module is integrated into the bio-agent detection system to operate as a network sensor.;To verify the model and FPGA sensor device, two experiments with different samples were carried out. The estimated values by dual-LED sensor were compared with the reference values, which were measured by the spectrum shift method. The results indicate that the thickness variations measured by the dual-LED sensor agree with the reference values well within the range from 2 to 15 nm.;Thus, the contribution of the thesis is developing a model to estimate sample layer thickness variation and its validation using the dual-LED detection system based on FPGA. The design and fabrication of the system is also main contribution in this thesis.;Keywords: Biosensor, Film Thickness Variation Measurement, Reflectometric Interference Spectroscopy (RIfS), Field-Programmable Gate Array (FPGA), Light Emitting Diode (LED)... |
