Dengue fever (DF) is an infectious disease spread by mosquitoes with a significantly rising rate of death over decades worldwide. Presently, the label-based ELISA method in detecting dengue virus (DENV) is time-consuming and laborious. Thus, label-free biosensor has been shown to be useful and capable to overcome the limitations by ELISA. In this thesis, the detection of dengue virus type-2 (DENV-2) deoxyribonucleic acid (DNA) using a field-effect transistor (FET) biosensor is introduced and demonstrated. Among various types of established field-effect transistor based biosensing technologies, silicon nanowire (SiNW) FET-based biosensor has proved to be a versatile class of potentiometric nano biosensor, are notable for their attractive characteristics, such as real-time, highly sensitive and label-free detection of a wide range of biomolecules. Therefore, this research aims to develop a label-free biosensor device with high sensitivity through accurate measurement to detect DENV-2 DNA using SiNW act as a transducer and creates electrical potential variations to control the conductivity of the source and the drain. The SiNW had been fabricated between the source and drain of the FET based on p-type Silicon-on-insulator (SOI) substrate, with the presence of back gate biasing, through top-down fabrication methods such as lithography and inductively coupled plasma reactive ion etching (ICP-RIE) technology. The surface morphological of the SiNW had been characterized via the nano-characterization technique, which is field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). Simultaneously, the element composition of the transducer was analyzed via Energy Dispersive X-ray (EDX). The surface modification was then performed by immobilizing the single-stranded DNA (ssDNA) dengue probes layer on a transducer surface through covalent binding, recognizing its complementary DNA target form immobilized double-stranded DNA (dsDNA). A complete device fabrication process with the smallest nanowire width obtained is 159 nm with a height of 11 nm. Electrical characterization is disclosed, starting with device validation using three different pH values of pH12, pH7 and pH4, and then testing with various target concentrations and analyzing selectivity. Through electrical measurement, the device gives a good response in current-voltage characteristic by coupling with a back gate in enhancing the accumulation of the hole conduction layer on the channel surface. The SiNW is validated as a transducer by testing with different pH where the fabricated device's sensitivity is 0.599 nA/pH. Meanwhile, the detection of DNA hybridization is shown for target concentration as small as 10 fM with the device sensitivity of 3.3 nAM-1. Hence, it shows that this device as a promising diagnostic platform for point-of-care testing (POCT) and have significant implications in medical healthcare.
