Applications of Transistor-Based Biochemical Sensors

Abstract

Transistor-based biochemical sensors feature easy integration with electronic circuits and non-invasive real-time detection. They have been widely used in intelligent wearable devices, electronic skins, and biological analyses and have shown broad application prospects in intelligent medical detection. Field-effect transistor (FET) sensors have high sensitivity, reasonable specificity, rapid response, and portability and provide unique signal amplification during biochemical detection. Organic field-effect transistor (OFET) sensors are lightweight, flexible, foldable, and biocompatible with wearable devices. Organic electrochemical transistor (OECT) sensors convert biological signals in body fluids into electrical signals for artificial intelligence analysis. In addition to biochemical markers in body fluids, electrophysiology indicators such as electrocardiogram (ECG) signals and body temperature can also cause changes in the current or voltage of transistor-based biochemical sensors. When modified with sensitive substances, sensors can detect specific analytes, improve sensitivity, broaden the detection range, and reduce the limit of detection (LoD). In this review, we introduce three kinds of transistor-based biochemical sensors: FET, OFET, and OECT. We also discuss the fabrication processes for transistor sources, drains, and gates. Furthermore, we demonstrated three sensor types for body fluid biomarkers, electrophysiology signals, and development trends. Transistor-based biochemical sensors exhibit excellent potential in multi-mode intelligent analysis and are good candidates for the next generation of intelligent point-of-care testing (iPOCT).

Keywords: biochemical sensor; field-effect transistor (FET); intelligent point-of-care testing (iPOCT); organic electrochemical transistor (OECT); organic field-effect transistor (OFET).

Figure 1

Structural diagrams of transistor-based biosensors. (a) Bottom-gate/bottom-contact transistor-based sensor. (b) Bottom-gate/top-contact transistor-based sensor. (c) Top-gate/bottom-contact transistor-based sensor. (d) Top-gate/top-contact transistor-based sensor. (e) Schematics of three transistor-based biochemical sensors.

Figure 2

Electrode structure images. (a) Optical image of the printed Ag electrodes, F8T2 organic active layer, and poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) gate electrode [38] (Copyright 2019 Elsevier). (b) Screen-printed S/D electrode’s scanning electron microscope (SEM) image [39] (Copyright 2022 Elsevier). (c) Optical image of the transistor channel [40] (Copyright 2014 Elsevier). (d) Optical microscopy image [41] (Copyright 2015 Elsevier). (e) SEM images of carbon nanotube (CNT) electrode patterns [42] (Copyright 2020 Elsevier).

Figure 3

Structures of FET-based biochemical sensors. (a) Structure of InZn_xO_y EGFET on PET flexible [26] (Copyright 2020 Elsevier). (b) Structural diagram of a field-effect transistor glucose sensor [27] (Copyright 2021 Elsevier). (c) Structure of an aptamer-field-effect transistor sensing system [44] (Copyright 2022 Science Advances). (d) Structural diagram of a cortisol biosensor. Reproduced from Reference [45] (Copyright 2021 Nature).

Figure 4

Examples of graphene field-effect transistor biochemical sensors. (a) Schematic illustration of the fabricated graphene nano-platelets electrolyte gate field-effect transistor (EGFET) [28] (Copyright 2020 Elsevier). (b) Schematic illustration of the solution-gated CVD graphene sensor [46] (Copyright 2022 Elsevier). (c) Schematic illustration of the rGON-FET biosensor for cellular Ca²⁺ detection [29] (Copyright 2023 Elsevier). (d) Schematic illustration of the selective K⁺ sensor [47] (Copyright 2013 Elsevier).

Figure 5

Examples of organic field-effect transistor biochemical sensors. (a) Illustrative diagram of the dopamine detection OFET sensor [48] (Copyright 2017 American Chemical Society). (b) Schematic illustration of the extended-gate-type OFET-based biosensor for detecting dopamine in human urine [49] (Copyright 2023 Elsevier). (c) Schematic illustration of the extended-gate type OFET biosensor for detecting lactate [50] (Copyright 2015 Elsevier). (d) Schematic of MIP-OFET structure for detecting cortisol [51] (Copyright 2023 Elsevier). (e) Schematic illustration of the flexible glucose OFET sensor [52] (Copyright 2022 Elsevier).

Figure 6

Examples of organic field-effect transistor biochemical sensors. (a) Schematic illustration of MWCNT-functionalized PEDOT nano-wires and its applications in K⁺ Sensors based on organic electrochemical transistors [53] (Copyright 2022 Elsevier). (b) Schematic of the perfusion system and microfluidic integrated OECT [55] (Copyright 2021 Elsevier). (c) Schematic drawings of the patch-type wearable cortisol sensor [56] (Copyright 2018 Science Advances). (d) Schematic architecture of flexible OFETs [67] (Copyright 2022 Elsevier).