Polyaniline-Based Biological and Chemical Sensors: Sensing Mechanism, Configuration Design, and Perspective

Abstract

By virtue of its tunable electrical conductivity, remarkable solution processing capability, and great biocompatibility, polyaniline (PANI) has been recognized as an attractive active material for use in biological and chemical ("bio/chemical") sensors. This Spotlight article focuses on the structure and characteristics of PANI-based materials and the corresponding device-level sensing performance. PANI-based bio/chemical sensors, such as chemi-resistive sensors, electrochemical sensors, and transistor-based sensors, are systematically elucidated based on device architecture and sensing mechanism. The corresponding structure−function relationships among PANI doping state, microscopic structure, local crystallinity, and their functionalities in three types of sensors have been systematically elaborated. Finally, the state-of-the-art progress in applications of these sensors and the corresponding breakthroughs in a broader context are outlined from the challenges to strategies.

Recent Progress in Biomedical Sensors Based on Conducting Polymer Hydrogels

“…PANI can be found in four different statesleucoemeraldine base, pernigranaline base, emeraldine base, and emeraldine saltdepending on its oxidation and doping state. The first two states are the insulating states, while the last two are conducting states based on doping and dedoping of the chain due to the acidic and basic substances in the environment . Because of this property, PANI has been extensively used in pH sensors .…”

Highly Stretchable, Ultra-Sensitive, and Self-Healable Multifunctional Flexible Conductive Hydrogel Sensor for Motion Detection and Information Transmission

“…This can solve the weak interface interaction between a rigid highly conductive filler and a flexible polymer matrix. Moreover, among many conductive polymers, polyaniline (PANI) and polypyrrole (PPy) are of low cost, easy to synthesize, stable in air, and with controlled physical properties. − Therefore, developing flexible multifunctional sensing materials utilizing conductive polymers such as PANI and PPy is of great interest to researchers. , …”

Multifunctional Fiber for Synchronous Bio‐Sensing and Power Supply in Sweat Environment

“…[ 7–12 ] Among the assorted biological electrode materials, aniline‐based polymers have been considered as prospective candidates for the assembling of smart fibers owing to their excellent biocompatibility, as well as impressive electrical conductivity and stiffness due to their π ‐ π conjugated aromatic backbone. [ 13–16 ] Such features have enabled the widespread application of aniline‐based polymers in various frontier fields, such as biosensing, in vivo neurophysiological monitoring and wearable electrochemical energy storage. [ 17–20 ]…”

“…[7][8][9][10][11][12] Among the assorted biological electrode materials, aniline-based polymers have been considered as prospective candidates for the assembling of smart fibers owing to their excellent biocompatibility, as well as impressive electrical conductivity and stiffness due to their 𝜋-𝜋 conjugated aromatic backbone. [13][14][15][16] Such features have enabled the widespread application of aniline-based polymers in various frontier fields, such as biosensing, in vivo neurophysiological monitoring and wearable electrochemical energy storage. [17][18][19][20] In general, the dissolution and processing of polyaniline (PANi) in its emeraldine salt (ES) form in common organic solvents remains an intractable challenge that significantly restricts its scale production.…”