Study on the label-free detection of biological species influenced by fluidic environment using underlap-FET biosensor

Abstract

In this thesis, the underlap-embedded FET is proposed for the FET-type bio sensor for label-free, sensitive, electrical detection of bio molecules in dry and wet environment. To investigate the effectiveness of the underlap device as a biosensor, the SBP-AIa which is the designed bio molecules for attachment to the silica surface and anti-AI were prepared. After the immobilization of the SBP-AIa, anti-AI was introduced for antigen and antibody binding. The drain current was significantly decreased by the binding of anti-AI. The decrement of drain current came from the negative charge characteristics of the anti-AI in buffer solution of pH 7.4. Subsequently, a set of control experiment was carried out to confirm the bio experimental results. From the selectivity test of AI antigen and antibody, it was conclude that the change in the drain current resulted only from the bio molecules in the underlap channel region. The drain current reduction was also shown for the result which device was exposed in air ambient. In the underlap device, the decrement of drain current came from the negative charges introduced on the underlap channel region, and therefore, it can conclude that biosensor can operate using the charge characteristic of bio molecules which is exposed in air ambient. For further investigation, additional bio experiment using biotin and streptavidin was performed. Because of negative charge characteristic of streptavidin in the pH 7.4, it showed similar tendency with SBP-AIa and anti-AI case.