film, fabricated with thin PTh-nanofibrillated cellulose synthesized by one-step oxidative

polymerization of 3-methyl thiophene onto nanocellulose film using FeCl3 as oxidant. The

fabricated film displayed good flexibility, high electrical conductivity, and mechanical

strength [15].

In an experimental-cum-theoretical study by Brazilian and Italian researchers, the

electronic and optical properties of PTh were enhanced by patterning resulting in an

organized internal structure of the material. A droplet of PTh solution deposited on a

surface was allowed to evaporate, during which a pattern of parallel strips was made on

it by an elastomeric stamp placed over it. This process made the atom chains linear to

each other, as they bring atoms and hold very close to each other in the same chain. After

migration, the electrons return to their starting point, where they emit and absorb light.

This nanostructured PTh is suitable for active photonic devices [16]. Owyeung et al.

fabricated a 3D transistor with multifilament threads, which was interconnected to logic

gates and an integrated circuit that paved a way for smart sutures and wearable tech­

nology for transdermal application. The multiplexed diagnostic device was created by

colloidal nanoparticles of silica supported with ion gel gated, linen thread-based tran­

sistors using P3HT which have been integrated with thread-based electrochemical sen­

sors, which are thin and flexible [17].

An atom transfer radical polymerization initiator-functionalized PTh was grafted with

a low glass transition temperature (Tg) (9.5°C) and hydrogen-bonded poly(acrylate ur­

ethane) side chains of varying lengths. It was observed that with increasing chain lengths,

the graft polymer became softer and stretchable, resulting in higher strain and lower

Young’s modulus, respectively, these properties are more desirable for flexible and

wearable electronics. Poly[5,5′-bis(2-butyloctyl)-(2,2′-bithiophene)-4,4′-dicarboxylate-alt-

5,5′-2,2′-bithiophene] substituted PTh derivative displays better charge mobility of

>0.1 cm²/V.s and stretchability of 400 stretch–release cycles than native PTh [18]. Doping

of PTh with PEG2000 and sodium p-toluene sulfonate as polymeric and anionic surfac­

tant dopants imparted superior mechanical flexibility (elongation-at-break of 110%), good

tensile strength (160 MPa), and tensile toughness of 133 MJ/m³, comparable to that of

spider silk (100–160 MJ/m³) [19]. Zokaei et al. fabricated PTh-based conducting fiber,

where PTh with tetraethylene glycol side chains (p(g42T-T) blended with PU which is a

combination of a semiconductor and insulator resulted with microfibers using the wet

spinning technique, as shown in Figure 23.3a [20]. Using dimethylformamide (DMF) as a

common solvent (p(g42T-T) and PU was dissolved, blended, and extruded in a coagu­

lation bath where the fibers are further collected by a take-up roller. With different

concentrations, microfibers with different diameters are fabricated as shown in

Figure 23.3(b–d). The fibers are collected in a collector as shown in Figure 23.3e and

showed the best reversible deformation and mechanical stability, as presented in

Figure 23.3f. Additionally, by doping with iron(III) p-toluenesulfonate hexahydrate fibers

exhibited conductivity up to 7.4 S/cm, flexibility up to 480%, and retained their con­

ductivity until elongation at break.

23.3.1 PANi

PANi for flexible bioelectronics relevance to applications that are specifically related to

the epidermal layer of tissue could be fabricated via 3D printing, electrospinning, laser

ablation, and lithography. 3D printing is an additive manufacturing technique that is

related to layer-by-layer fabrication. Among several subtypes available fused deposition

printing, inkjet printing, direct printing, and stereolithography are widely used. Metallic

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Bioelectronics