conductivity and PSS for cation conductivity. This material has limitations due to its low

mechanical stability, so it is used together with additives such as acrylamide and poly(vinyl

alcohol), or in combination with higher mechanical resistant polymers, for example, Cuttaz

et al. synthesized a composite material of PEDOT: PSS and polyurethane (PU), for the

manufacture of flexible electrodes using laser micromachining, finding that dispersions of

10% to 15 % of PEDOT: PSS in PU achieve a balance between electrical and mechanical

properties, helping to increase the neuronal cells survival compared to pristine PU [18].

PPys become conductors when oxidized due to the delocalized electrons cloud throughout

the polymeric network; these materials also present biocompatibility, thermal stability, and

ease of synthesis, characteristics that allowed the manufacture of actuators based on PPy

films doped with BF4

-, which have potential application in the manufacture of artificial

muscles [19]. Finally, PANI is a low-cost conductive polymer due to its accessible synthesis,

which retains the characteristics of biocompatibility and chemical stability. The PANI

properties may be enhanced by combining it with secondary materials; for example, Cui

et al. developed a chitosan-PANI patch that tries to modulate the electrophysiology of

cardiac tissue and shows little inflammatory response in in-vivo assays [20].

Recent research works have sought the formulation of structures with multiple func­

tions, which shows other characteristics in addition to charge transport, such as optically

active, catalytic properties, or are self-repairing. So, Uzuncar et al. presented a PANI: PSS

copolymer that was used for the fabrication of NH4

+ sensors and urea biosensors by

coupling with the enzyme urease, which showed high sensitivity and selectivity in

modeled urine samples [21].

2.2.2.1 Allotropes of Carbon

In addition to conductive polymers, allotropes of carbon, such as graphene and carbon

nanotubes (CNTs), are a good alternative for the development of bioelectronics detection

FIGURE 2.2

Molecular structures of the most used conductive polymers, PEDOT: PSS, PPy, and PANI.

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Bioelectronics