Recent Advances in Flexible Field‐Effect Transistors toward Wearable Sensors

Abstract

The introduction of the "Internet of Things" (IoTs) concept has spawned a series of research and development of wearable sensors. Flexible field-effect transistors (FETs) are considered to be potential sensing devices due to the variety of material utilization and the self-amplifying function on electrical signals. FETs have demonstrated the ability of detecting different kinds of external stimuli and continuous monitoring functionalities. Herein, the recent progress achieved by the academia in wearable sensors based on flexible FETs, including pressure, temperature, chemical, and biological analytes, which are vital for the manufacturing of smart wearable devices, is summarized. The sensing mechanism for different sensors is introduced and an in-depth discussion is presented, including material engineering, problems at the current stage, and future challenges.

Construction of Photoelectrochemical DNA Biosensors Based on TiO2@Carbon Dots@Black Phosphorous Quantum Dots

“…After adding a high concentration of Test DNA for completely non-complementary pairing, the photocurrent did not decrease significantly, while the photocurrent of the fully complementary pairing control group at the same concentration reduce to 1.1 µA, indicating that the constructed PEC detection method had good specificity for T-DNA. In the future, the ITO substrate could be replaced by a flexible material, such as conductive polymers [25], and then the prepared PEC biosensors could be used as portable detection devices.…”

Wearable electrochemical biosensors to measure biomarkers with complex blood-to-sweat partition such as proteins and hormones

“…A similar tripartite arrangement for WEBs' electrodes is applied in either transistor (e.g., field-effect transistors, FETs) or electrochemical cells (e.g., screen-printed electrodes, SPEs) (Fig. 3a , g ): i) point for control of the electrochemical energy (i.e., G in FETs or RE in SPEs), ii) point for energy inlet (i.e., S in FETs or WE in SPEs) and iii) point for energy outlet (i.e., D in FETs or CE in SPEs) [ 79 – 81 ]. Of course, the three quoted categories are relative to the measurement format and associated carriers' charge movement, in such a way that most of them for sweat monitoring have a coplanar disposition concerning the control/inlet/outlet electrodes.…”

“…FETs are solid-state electrodes that commonly operate by a tunable 2–30 V. These kinds of transistors have efficient electrical power consumption, emit negligible heat, and, as any transistor, may self-amplify the electrical signals [ 81 , 87 , 119 ]. WEBs based on FETs have a basic architecture that contains a tripartite terminal system (i.e., G, S & D) and a semiconductor channel that serves as a bridge for electric flow between S and D (Fig.…”

“…Then, the inlet signal I GS is altered, modifying the outlet I DS into the channel, amplified for further readout processing. In brief, if any of the three parameters V DS , I DS , or V GS vary, the other two will fine-tune their behavior either linearly, e.g., any V GS increase leads to a significatively I DS increase or saturated, e.g., I DS is not modified despite any increase in any V DS [ 79 , 81 ]. In a transfer plot (Fig.…”

Ten Years Progress of Electrical Detection of Heavy Metal Ions (HMIs) Using Various Field-Effect Transistor (FET) Nanosensors: A Review

“…This attractive factor of high current on/off ratios plays an important role in sensor response time. The higher the current on/off ratios, the faster the response speed of the sensor [ 215 ].…”