Abstract
Conventional flexural plate-wave (FPW) transducers have limited applications in biomedical sensing due to their disadvantages such as high insertion loss and low quality factor. To overcome these shortcomings, we propose a FPW transducer on a low phase velocity insulator membrane (5-μm-thick SiO 2 ) with a novel groove-type reflective grating structure design. Additionally, a cystamine self-assembly monolayer and a glutaraldehyde cross-linking layer are implemented on the backside of the FPW device to immobilize alpha-fetoprotein (AFP) antibody. A FPW-based AFP biosensor with low detection limit (5 ng/mL ) can be achieved and used to measure the extreme low concentration of AFP antigen in human serum for early detection of hepatocellular carcinoma. The proposed FPW-based AFP biosensor also demonstrates a very high quality factor (206), low insertion loss (−40.854 dB ), low operating frequency (6.388 MHz), and high sensing linearity (90.7%).
Highlights
Over the past few decades, many tumor markers have been proposed as important indicators to screen cancer patients in clinical applications
To enhance the quality factor and reduce the insertion loss and phase velocity of a flexural plate-wave (FPW)-based biosensor, this paper introduces a novel groove-type reflective grating structure (RGS) and adopts a low phase velocity insulator membrane (5-μm-thick SiO2) to replace the conventional silicon-based membrane
4.1 Quantification Analysis of the AFP Antibody-Antigen Immobilized on 96-Well Micro-Titer Plate and Si∕SiO2∕Si3N4∕Cr∕Au∕ Cystamine∕Glutaraldehyde Chip
Summary
Over the past few decades, many tumor markers have been proposed as important indicators to screen cancer patients in clinical applications. Any small changes in the mass of floating thin plate of the FPW transducer resulting in a change of the acoustic wave velocity can be measured indirectly as a change in center frequency of the FPW-based biosensor.[9,10,11,12,13,14,15,16,17,18,19] the high insertion loss and low quality factor of conventional FPW-based biosensors have limited their applications. Utilizing micro-electromechanical systems (MEMS) and cystaminebased SAM technologies, this study demonstrates a FPWbased biosensor with low insertion loss, low operating frequency, high quality factor, and sensing linearity for detecting low concentration of AFP antigen in human serum
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