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Design and Fabrication of Highly Performance EGFET and Application in Thrombin Detection

Published in : IEEE Sensors Journal (Volume: 25, Issue: 3, February 2025)
Authors : Wang Yiqing, Ding Song, Jiang Jidong, Liu Tao, Wang Ting, Zhang Minghui, Zhang Wei, Zhu Xinglong
DOI : https://doi.org/10.1109/JSEN.2024.3514187
Summary Contributed by:  Yiqing Wang (Author)

Ion-Sensitive Field-Effect Transistors (ISFETs) are electronic devices designed to detect ion concentrations, mainly for pH measurement. Extended-Gate FETs (EGFETs), a derivative of ISFETs, improve usability by separating the sensing and transducer regions. This design minimizes contamination, simplifies packaging and testing, and enables customizable, replaceable sensors. Consequently, EGFETs are widely used in biomedical, environmental, and biological applications. Despite their advantages, further sensitivity and structural design improvements are still necessary.

In this study, a 3D simulation model of the EGFET was developed using Silvaco Technology Computer-Aided Design software, incorporating Hafnium (IV) oxide (HfO₂) and Indium (III) oxide (In₂O₃) as the primary materials. The simulation provided insights into the device's internal physical structure and guided the selection of optimal material and structural parameters.

The EGFET device was fabricated using magnetron sputtering and other techniques based on the optimal parameters obtained from simulations. The successful deposition and uniformity of the sensitive layer were confirmed through characterization methods, including X-ray diffraction (XRD), Scanning electron microscopy (SEM), and Energy-dispersive X-ray spectroscopy (EDX).

Experimental results demonstrated that the fabricated EGFET exhibited outstanding performance across a pH range of 2–12, achieving a pH voltage sensitivity of 110.91 mV/pH, a linearity (R²) of 97.67%, and a relative standard deviation (RSD) of threshold voltage of 3.51%. Additionally, the device showed low hysteresis voltage (4.5 mV) and drift rate (1.26 mV/h).

Thrombin was selected as the target biomarker to evaluate the practical biosensing potential of the EGFET due to its critical involvement in cardiovascular diseases and tumor development. Thrombin detection presents considerable challenges due to its wide concentration range and stringent detection accuracy requirements. Conventional detection approaches, including ultracentrifugation-mass spectrometry, fluorescence assays, and resonance light scattering techniques, are often limited by their dependence on sophisticated instrumentation and complex operational procedures.

High-sensitivity thrombin detection was achieved by functionalizing the EGFET sensing surface with aptamer-conjugated detection probes. The biosensor demonstrated a wide linear detection range (1–10,000 pM) with excellent correlation (R² = 0.9564). It also showed remarkable specificity in discriminating thrombin from potential interferents like Immunoglobulin G (IgG), bovine serum albumin (BSA), and prostate-specific antigen (PSA).

Building upon this EGFET, the researchers developed a handheld thrombin detection system capable of completing concentration measurements within 30 minutes - significantly faster than conventional clinical diagnostic methods (typically requiring 1-2 hours). The development of this portable detection platform further demonstrates the practical advantages of EGFET technology in terms of operational convenience and detection efficiency.

The experimental results demonstrate that the simulation-optimized EGFET design achieves excellent performance in both pH sensing and high-sensitivity biomarker detection, providing a significant reference for future biosensor miniaturization and portable development. Furthermore, the replaceable sensitive area design of the EGFET reduces the cost of device loss.

The proposed device's outstanding sensitivity, remarkable stability, and portability give it broad application prospects in biomedical testing and environmental monitoring. Future research directions should focus on exploring the EGFET's potential for detecting additional biomarkers and further optimizing the integration level and user experience of handheld detection devices.

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