| Summary: | 博士 === 國立中山大學 === 電機工程學系研究所 === 100 === Utilizing self-assembled monolayer nanotechnology, micro-electro-mechanical systems (MEMS) and IC technologies, a novel flexural plate-wave (FPW) biosensor is developed in this dissertation for detecting the immunoglobulin-E (IgE) concentration of human serum. The acoustic waves of the proposed FPW devices are launched by the 25-pair inter-digital transducer (IDT) input electrodes and propagated through the 4.82 μm-thick Si/SiO2/Si3N4/Cr/Au/ZnO floating thin-plate. Since the thickness of such floating thin-plate is much smaller than the designed wavelength of FPW device (80 μm), most of the propagating wave energy will not be dissipated into outside of thin-plate and the mass sensitivity is very high. To further reduce the insertion loss of the proposed FPW devices, two 3 μm-thick Al reflection grating electrodes (RGE) are designed beside the input and output IDTs.
To implement a FPW-based IgE biosensor, a Cr/Au electrode layer has to be deposited on the backside of the floating thin-plate to serve as a substrate for further coating the cystamine SAM/glutaraldehyde/IgE antibody layers. Once the IgE antigens of human serum are bound to the IgE antibody layer, the small change in the mass of floating thin-plate will result in a shift of center frequency of the testing FPW-based biosensor. Compared to the reference FPW biosensors, the shift of center frequency generated by the testing FPW biosensor under different IgE antigen concentration can be detected by commercial network analyzer or the frequency-shift readout system developed by our collaboration laboratory (VLSI Design Lab. of NSYSU).
Compared to commercial enzyme linked immunosorbent assay (ELISA) analyzer (sample volume >25 μl/well, testing time >60 min, dimension>40 cm ×30 cm×10 cm), the implemented FPW-based IgE biosensor presents a smaller sample volume (<5 μl), faster response (<10 min) and smaller size (<9 mm×6 mm×0.5 mm). In addition, a very low insertion loss (-9.2 dB), a very high mass sensitivity (-6.08×109 cm2 g-1) and a very high sensing linearity (99.46 %) of the proposed IgE biosensor can be demonstrated at 6.6 MHz center frequency. This study successfully developed a novel FPW-based allergy biosensor by MEMS technology, which has great potential to be further applied into point-of-care testing (POCT) microsystem.
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