review articles in recent years. Readers are advised to go through these review articles for

in-depth details. Here in this chapter, we would limit ourselves to the inclusion of con­

ductive hydrogel materials for bioelectronics.

Reasonable signal transduction traversing the biotic/abiotic interface is vital for current

bioelectronics design and operation. Conducting hydrogels are promising materials that

can remove the disparity between the biotic and abiotic phases. They can offer effective

and reliable signal transduction between bioelectronic devices and tissue. Electronic

devices are rigid and dry while biological tissues are soft and wet causing an increase in

interfacial impedance due to scar tissue formation. Furthermore reduction in stimula­

tion/recording efficacy is observed due to an increase in tissue–electrode distance. Due to

the structural similarity of hydrogels with natural tissue, it can function as an excellent

interface between electrode-electrolyte as well as biological soft and synthetic hard

materials. Owing to ionic as well electronic conductivity of conducting hydrogel, they

find applications in neural electrodes, artificial skin, and electronic tongue as well as in

various implants. Furthermore, properties of conducting hydrogels such as toughness,

stretchability, and biocompatibility can be easily modulated and additional properties

required for bioelectronic applications such as self-healing and shape-memory may also

be incorporated. Additionally, their high water holding characteristic facilitates the

exchange of biological molecules and markers across interfaces. Earlier inorganic ma­

terials such as metal electrodes and silicone were widely used for bioelectronic but

they differ intrinsically in terms of chemical and mechanical properties as compared to

body tissue. This critical difference causes serious problems such as nonconforming

contact between the devices and the skin or tissue, unstable signal collection, as well as

causing inflammatory responses in the body. Currently, most bioelectronic devices are

used in the form of electrodes that interact with biological systems and collect/deliver

various bioelectronic signals in different parts of the body such as skin, brain, spinal

cord, and heart.

18.2 Conducting Polymers

Conducting polymers (CPs) facilitate electronic pathways within the polymer backbone.

Examples of commercially used CPs are poly(p-phenylene), polyaniline (PANI), poly­

pyrrole (PPy), polythiophene (PTh), poly(3,4-ethylene dioxythiophene) polystyrene sul­

fonate (PEDOT: PSS), polyphenazine (PPz), polycarbazole (PCz), and their derivatives.

CPs show high stable electronic conductivity and thus have gained quite a popularity in

the field of bioelectronics. CPs have been widely applied in biosensors, bio-electrodes,

enzyme immobilization, and biomedical devices. Among others, PANI, PPy, and PEDOT

are the most commonly employed conducting polymers in bioelectronics applications

due to their high conductivity, biocompatibility, good water dispersibility, and high

stretchability. The PEDOT usually doped with polystyrene sulfonate (PSS) is most pop­

ular because of its highly stable electrochemical conductivity combined with a narrow

bandgap making it a suitable candidate for several electroanalytical biosensing applica­

tions as well as for the fabrication of platforms for tissue engineering applications.

Thiophene-based polymers have also gained popularity due to their stability and high

conductivity which can be varied with dopants. CPs have been integrated with biosensors

for the determination of several chemical species of biological importance including

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