para-toluenesulfonic acid (pTSA) served as a dopant. PPy modification of SF drastically

improved elastic modulus and ultimate tensile strength. Similar to SF, sodium alginate

(SA) is one of the well-known biomaterials for tissue engineering applications. However,

combining SA with dopamine functionalized PPy (DAPPy) nanofibers increased its

stretchability by more than 800% [30]. To prepare hybrid hydrogels, different amounts

of DAPPy nanofibers were added to SA and cross-linked with borax. The prepared for­

mulation displayed fast healing capability as well as arbitrary moldable ability.

Considering energy storage applications, a miniaturized device was fabricated. Peelable

nickel nanocone arrays (NNAs) and polypyrrole nanotubes (PPyNTs) were used as

conductive frameworks and active materials, respectively, to prepare patterned inter­

digital electrodes [31]. PPyNTs were deposited on the NNA using electrodeposition. The

fabricated device showed superior long-term cycling performance.

On a similar note, hollow PPy/cellulose (PC) hybrid hydrogels were reported as energy

storage systems. PPy was deposited electrochemically using a three-electrode system. The

designed hollow PC hybrid hydrogels were found to achieve significant enhancement

in terms of mechanical strength and flexibility. In an attempt to develop a material

possessing human skin-like mechanical compliance, PPy-rGO-PPy nanosheets modified

gelatin hydrogel was proposed [32]. The nanohybrids were synthesized by interface self-

assembly, which avoided the use of oxidants and dopants. The as-prepared sandwich-like

nanosheets had a wrinkled appearance and showed high stretchability and thermo­

responsive behavior. PPy coated cellulose nanocrystals (CNC) and cellulose nanofibers

(CNF) were used to reinforce PVA to prepare a biocompatible electronic skin sensor

system, as shown in Figure 23.4c. CNC and CNF were made by ultrasonication and then

PPy polymerization was initiated after mixing monomer followed by FeCl3 and APS [29].

Initially, CNC and CNF suspensions were prepared by ultrasonication. Then, a pyrrole

monomer was added to each dispersion to make a homogeneous mixture. Following this,

the polymerization was initiated by adding FeCl3 and APS. Meanwhile, a PVA solution

was prepared in Milli-Q water. Finally, the nanocomposites were dropwise mixed with

PVA solution. The resulting composite was proposed to show enhanced mechanical

properties due to hydrogen bonds present in the PPy network, nanocomposite, and PVA.

Moreover, Fe⁺³ ions present in the oxidant can chelate with the composite network fur­

ther increasing its strength.

23.3.3 PA

PA is insoluble, making it very difficult to process it for a range of biomedical applica­

tions and surface modifications. Since any kind of chemical modifications in the polymer

leads to a change in their electronic or mechanical properties, this, hereby hinders any

possible chances for PA to bind any biological molecule.

23.3.4 PEDOT

Doping PEDOT with polystyrene sulfonate (PSS) results in PEDOT:PSS polymer with

extremely high electrochemical stability, solution processability, high transparency in

the visible range, and a very narrow bandgap, useful for the detection of biomolecules

like uric acid, ascorbic acid (AA), glucose, dopamine (DA), metal ions, and also in

tissue engineering applications like fabrication of stimuli-responsive scaffolds. Ko et al.

fabricated flexible sensor PEDOT:PSS with graphene oxide (GO) to determine DA.

Polymerization and simple electrophoretic deposition of GO and EDOT:PSS dispersed

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Bioelectronics