Biomedical Engineering Reference
In-Depth Information
semiconductor that is commonly used as a channel material in organic i eld
ef ect transistors (OFET), is reported to exhibit good strain sensitivity [41, 42]
and also has a Young's modulus nearly matching with that of SU-8. h e most
popular deposition process for Pentacene is vacuum sublimation. h is allows
uniform deposition of pentacene layers and the deposition process is done at
room temperature making it suitable for polymer substrates [43]. OFETs have
a huge potential in realizing large-area, mechanically l exible, lightweight and
low-cost devices and circuits such as paper-like displays, radio frequency
identii cation tags, and large area sensors on l exible substrates. However,
the ef ect of strain on the electrical behaviour of pentacene based OFETs has
always been a concern while discussing the reliability of OFETs for l exible
electronics applications and dif erent device design ideas to overcome this
ef ect is an on-going research for realizing ultra-l exible OFET devices and
circuits [44-46]. h ere are a very few reports available in literature that inves-
tigated the ef ect of bending induced strain on change in current of pentacene
OFETs [43-47, 48]. h is negative aspect of dependence of electrical behav-
iour on bending induced strain in pentacene OFETs for l exible electronics
could be utilized in a positive way in realizing sensor applications using pen-
tacene. h e idea was to integrate pentacene based OFETs as strain sensor
in place of simple piezoresistor coni guration for microcantilevers. h is was
highly benei cial as the resistivity of pentacene thin i lms were known be very
high and the transistor coni guration would support the arrays of sensors
with built-in switching matrix using these integrated OFETs.
h e device concept is to embed a pentacene based OFET inside an
SU-8 microcantilever as shown in Figure
9.10. h is novel device named
I
ON
= I
0
I
ON
= I
0
-
I
Nanomechanical motion
I
Figure 9.10
Concept of an 'Organic CantiFET' device [28].
