Abstract
In the last two decades, various flexural plate-wave (FPW)-based biosensors with low phase velocity, low operation frequency, high sensitivity, and short response time, have been developed. However, conventional FPW transducers have low fabrication yield because controlling the thickness of silicon/isolation/metal/piezoelectric multilayer floating thin-plate is difficult. Additionally, conventional FPW devices usually have high insertion loss because of wave energy dissipation to the silicon substrate or outside area of the output interdigital transducers (IDTs). These two disadvantages hinder the application of FPW devices. To reduce the high insertion loss of FPW devices, we designed two focus-type IDTs (fan-shaped and circular, respectively) that can effectively confine the launched wave energy, and adopted a focus-type silicon-grooved reflective grating structure (RGS) that can reduce the wave propagation loss. To accurately control the thickness of the silicon thin-plate and substantially improve the fabrication yield of FPW transducers, a 60 °C/27 °C two-step anisotropic wet etching process was developed. Compared with conventional FPW devices (with parallel-type IDTs and without RGS), the proposed FPW devices have lower insertion loss (36.04 dB) and higher fabrication yield (63.88%). Furthermore, by using cystamine-based self-assembled monolayer (SAM) nanotechnology, we used the improved FPW device to develop a novel FPW-based carcinoembryonic antigen (CEA) biosensor for detection of colorectal cancer, and this FPW-CEA biosensor has a low detection limit (5 ng/mL), short response time (<10 min), high sensitivity (60.16–70.06 cm2/g), and high sensing linearity (R-square = 0.859–0.980).
Highlights
Various acoustic microsensors have been developed for molecular mass detection in the last two decades, including thickness shear mode (TSM), surface acoustic wave (SAW), shear horizontal acoustic plate mode (SH-APM), and flexural plate-wave (FPW) [1,2,3,4,5,6,7]
FPW devices are most suitable for applications in clinical, environmental, biological, and biomedical detection because they have low phase velocity, low operation frequency, small radiation loss in the testing liquid, high sensitivity, and short response time
Since the concentration of carcinoembryonic antigen (CEA) is an important indicator of colorectal cancer, the developed CEA biosensor, which has low insertion loss and high fabrication yield, can enhance the detection of colorectal cancer
Summary
Various acoustic microsensors have been developed for molecular mass detection in the last two decades, including thickness shear mode (TSM), surface acoustic wave (SAW), shear horizontal acoustic plate mode (SH-APM), and flexural plate-wave (FPW) [1,2,3,4,5,6,7] Among these acoustic microsensors, FPW devices are most suitable for applications in clinical, environmental, biological, and biomedical detection because they have low phase velocity, low operation frequency, small radiation loss in the testing liquid, high sensitivity, and short response time. Ratio, we first introduced focus-type metal-thinlaunched flexural plate-wave, reduce the insertion energy loss, and increase the signal-to-noise film. Since the concentration of CEA is an important indicator of colorectal cancer, the developed CEA biosensor, which has low insertion loss and high fabrication yield, can enhance the detection of colorectal cancer
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