electrodes like platinum, carbon electrode, and gold are conductive and well explored as

implantable devices and proved with long-term stimulation performance. Here comes a

need for 3D printable hydrogel with properties of mimicking extracellular matrix,

with water retention. Furthermore, PANi-based electric conductive hydrogels can be

utilized as electrodes for amplification of signals at the bioelectrode interface and have

been reported to have enhanced cellular adhesion, proliferative, and differentiation [21].

Pan et al. fabricated PANi hydrogels via direct inkjet printing with different layers of

phytic acid and for glucose sensing, which resulted in good electronic conductivity.

Owing to PANi low processibility for bioink, it is often mixed or blended with different

biocompatible polymers like silk fibroin (SF), polycaprolactone (PCL), and gelatin me­

thacrylate (GelMA). GelMA/PANi hybrid matrix hydrogel was fabricated with micro­

architecture showed enhanced electrical properties than GelMA, a form of denatured

collagen, and biocompatible with 10T1/2s cells [22].

For damaged cardio myocardium, bioelectric patches are required to restore the electric

signals and it should be operational for a longer duration. Hoang et al. fabricated the laser-

ablated chitosan sutureless patches with PANi on its surface with micro-architecture-

controlled porosity, good mechanical strength, and large surface area. Here, porosity varied

to nearly 40% and with good conductivity, these adhesive patches can adhere to tissues

after exposure to LED light [23]. Electrospinning, which is a cost-effect technique to fab­

ricate nanofibers, has limitations in its solvent selection for PANi. With the development of

recent technologies and machines, researchers can get the aligned PANi nanofibers and

thereby used in many biomedical applications. Electrospun PANi and its different com­

posites are profoundly used in biomedical applications, which not only include electrical

stimulation-based tissue regeneration like neural, cardiac functionality but also have ex­

plored the tissue engineering fields.

Jiahui He et al. fabricated the skin-repairing PCL-chitosan grafted PANi via electro­

spinning with antibacterial as well as good cell compatibility and proliferation. Moreover,

this nanofiber graft was found to be more effective than Tegaderm and pure PCL in terms

of wound healing [24]. The Bertuoli group fabricated the uniaxial and coaxially aligned

PANi tagged dodecylbenzene sulfonic acid with polylactic acid (PLA) for cardiac bio­

medical application. Later, interestingly they reported that with the addition of PLA,

electrical conductivity was also increased and PANi release into the culture media at­

tributed to a decrease in the cells [25]. In the coming years, PANi-based composites and

nanofibers would provide a road map in health care applications.

23.3.2 PPy

The most common technique in general to manufacture stretchable systems is using in­

trinsically flexible substrates such as poly(dimethylsiloxane) (PDMS), polyurethane (PU),

natural rubber (NR), etc. A nylon membrane (NM) was coated with PPy to achieve a su­

percapacitor with outstanding electrochemical performance [26]. The composite membrane

was synthesized by interfacial polymerization, as depicted in Figure 23.4a. Utilizing this

strategy, a stretchable conductive PPy/PU strain sensor was prepared using in-situ poly­

merization [27]. The solidified PU substrates first reacted with pyrrole monomer containing

sodium salt and later ferric nitrate and 2-sulfosalicylic acid hydrate solution and used as an

oxidizing and stabilizing agent, respectively to carry out oxidation. The resultant PPy/PU

composite showed maximum elongation of 420% with a resistivity of 8.364 Ω·cm. In another

report, flexible composite films were synthesized by combining PPy with a series of polyol

including pentaerythritol ethoxylate (PEE), PEG, polypropylene glycol (PPG), and

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Bioelectronics