Biosensing Detection - Bioinspired Approaches for Human-Centric Technologies - page 78

semiconductors, organic materials offer attractive characteristics in terms of
mechanical properties, possibility of chemical engineering, and interaction with
visible light. Importantly, the technology required for processing materials and
realizing devices is relatively cheap and easy, and it fits well with transparent,
bendable, rollable, and lightweight plastic substrates. The counterbalance to be paid
back is reduced electronic mobility and poor environmental stability. Major efforts
are currently focusing on improving performances of solar cells and transistors,
which are expected to represent the next applications to be delivered on the market.
At the same time, the research community is now experiencing a “second birth”
of organic electronics, approaching the last, unexplored frontier: the interaction
with a living system, in the attempt to realize new-concept, organic-based human-
machine interfaces. The mixed term “organic bioelectronics” was used for the first
time in 2007 by Berggren and Richter-Dahlfors in a seminal review (Berggren and
Richter-Dahlfors 2007 ), by referring to the application of organic electronics in the
broad field of life sciences. Historically, the key milestone of conducting and
semiconducting polymers for biomedical applications stands in their use as active,
functional materials, opposed to the adoption as standard passive components for
coatings. Since then, the field has been growing at a surprisingly fast rate, as
documented by the increasing number of publications, the number of funded pro-
jects in the field, and the organization of focused symposia at international

conferences.
The strong interest manifested by the community stems from the peculiar
properties of organic semiconductors: polymers are able to offer innovative, valu-
able solutions where traditional technologies, based on silicon or other inorganic
semiconductors, fail. Besides the possibility of adopting cheaper and more versatile
processing technologies, specifically suited to the in vivo applications, organic
semiconductors, and more specifically conjugated polymers, show superior bio-
compatibility and adaptability to work at the interface with living tissues. At the
macroscopic level, the soft surface of polymer thin films represents an ideal
substrate to grow cells for in vitro studies as well as for in vivo interfacing even
with extremely delicate tissues, such as the retina, the central and peripheral neural
tissue, the intestinal and kidney epithelium, etc. At a submicroscopic level, the
polymers' softness finds an explanation in their peculiar conjugated structure,
constituted by alternating single and double carbon bonds, which is indeed very
similar to the structure found in many biological molecules (the retinal molecule,
for instance). Moreover, conducting and semiconducting polymers offer the unique
capability of mixed electronic conduction and ionic conduction, thus opening a new
interconnection perspective with living matter.
All mentioned properties make this class of materials extremely attracting for
applications in biomedical engineering, neuro-technology, and life sciences. In few
years, many devices have been demonstrated, able to work both in vitro and in vivo.
In some cases, their performances outperform those reported so far by adopting
standard, inorganic technologies and have already reached the necessary develop-
ment for preclinical and clinical application. In the following, we will present some
notable (even though not exhaustive) examples of in vitro and in vivo applications.