Page 133 - Organic Electronics in Sensors and Biotechnology

110 Cha pte r T h ree

electrically independent and that organic transistors are only used to
address sensitive (pressure or thermal) elements. The arrays are less
sensitive than human skin, but already mark an improvement over
previous efforts, while sensing temperatures in the range of 30 to
80°C. Moreover, the structure is flexible enough to be rolled or bent
around a 2 mm bending cylinder. Someya estimates that his e-skin
will be commercially available within a few years, and in the near
future it will be possible to make an electronic skin that has a function
that human skin lacks by integrating various sensors not only for
pressure and temperature, but also for light, humidity, strain, sound,
or ultrasonic.
Moreover, it could also be possible in the next years to develop
electronic skin completely made of organic transistors. In particular,
the possibility of realizing strain and pressure sensors that can act
at the same time as switch and as sensor without the need of any
further sensing element will be interesting. Moreover, flexible chemo-
sensitive transistors, biosensors, and temperature sensors could be
obtained with the same technologies, allowing new challenging and
smart features for this application.

3.4.2 E-Textiles
There is an increasing interest in the emerging area of e-textiles,
meaning with this term the idea of endowing garments and fabrics
with new electronic functions, in particular aimed at monitoring
25
physiological parameters in patients and in subjects exposed to par-
ticular risks or external harsh conditions. 26
Strain and pressure sensors for measuring body characteristics
are particularly interesting for this kind of application because
they could enable one to measure a wide set of parameters such as
posture, breathing activity, etc., in a totally non-intrusive way. This
characteristic is in fact very interesting for practical applications.
For instance, it allows doctors to monitor the patient status in real
time, 24 hours per day; additionally, it allows a better quality of
life for patients who do not perceive them as invasive monitoring
systems.
Basic specifications for this application are rather similar to those
listed for electronic skin. In addition, these systems, being in contact
(or close) with the human body, must comply with strict safety stan-
dards. Organic field-effect sensors developed on plastic flexible films
are good candidates to accomplish this function as they can be assem-
bled in arrays on flexible substrates to be applied on the fabric itself.
At present, first attempts of strain sensors on garments are made
with piezoresistive stripes deposited on the garments. 27–32 In this case,
the detection is made through piezoresistive tracks running on the
fabric along, for example, a sleeve or parallel to the chest in a T-shirt
(Fig. 3.19). In this way, the movement results in a deformation of the