Development of an FPW Biosensor with Low Insertion Loss and High Fabrication Yield for Detection of Carcinoembryonic Antigen

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).

ZnO nanorod‐based Love wave delay line for high mass sensitivity: a finite element analysis

“…The sensitivity of the proposed device is higher than the conventional QCM and FPW devices. The FPW device offers high sensitivity at a low frequency of operation but suffers from poor fabrication yield and high insertion losses [57,58]. The coupled resonance device also outperforms the SiO 2 /ZnO film LW biosensors [54,59] and other microcavity-based LW devices reported in the literature [25].…”

Piezoelectric MEMS—evolution from sensing technology to diversified applications in the 5G/Internet of Things (IoT) era

“…Reprinted from [116], Copyright (2019), with the permission from Elsevier. (d) A flexural plate wave (FPW) biosensor for carcinoembryonic antigen (CEA) detection [120]. Reproduced from [120].…”

Acoustic Biosensors and Microfluidic Devices in the Decennium: Principles and Applications

“…Love mode and FPW SAW mode sensors have been reported for the real-time, labelfree detection of CEA, from both human serum as well as from exhaled breath condensate with an LOD varying from 1 ng/mL to as low as 37 pg/mL [258,261,271,273,287]. A Love mode SAW delay line biosensor using ST-cut quartz with Au IDT and sensing area operating at 120 MHz was reported, with an LOD of 0.31 ng/mL for CEA detection [287].…”

“…The real-time monitoring of phase shift showed an enhanced phase change after the addition of nanoprobes due to mass amplification, as reported in Figure 28c. An FPW sensor operating at 20 MHz was reported for the detection of CEA utilizing 1 µm c-axis oriented ZnO thin film with a detection limit of 5 ng/mL [261]. A novel fanshaped and circular IDT and reflectors were introduced to minimize the insertion loss (IL) in the device, due to the loss of acoustic energy to the bulk Si substrate in the FPW device.…”