Biomedical Engineering Reference
In-Depth Information
I
0
(V
GS
= V
DS
= -40V) = 19.05 nA
250
3.0 × 10
-8
= 1.5 × 10
-4
ε
ε
= 3.1 × 10
-4
ε
= 4.7 × 10
-4
ε
200
2.0 × 10
-8
= 6.2 × 10
-4
150
1.0 × 10
-8
100
0.0
I/I
[%]
-40
-30
-20
-10
0
Gate voltage [V]
50
V
TH
/V
TH
[%]
Exponential fit
0
0.02
0.04
0.06
Strain [%]
0.08
0.10
Figure 9.14
Percentage change in drain current, saturation i eld ef ect mobility
and threshold voltage are plotted as a function of percentage strain. Inset : Transfer
characteristics of organic CantiFETs under dif erent strain conditions. Inset shows the
IDS-VDS characteristics (@VDS = -40 V) under identical strain conditions.
strain gauge [20] and the MOSFET embedded silicon cantilevers [49]. h e
del ection sensitivity of organic CantiFET sensors was at least 50 times higher
compared to the SU-8 microcantilevers with gold as a strain gauge and 15
times higher compared to that of MOSFET embedded silicon cantilevers. h e
extracted surface stress sensitivity value for organic CantiFET is at least three
orders of magnitude higher in comparison to that of SU-8 microcantilevers
with integrated Au strain gauge (0.3 ppm [mN/m]
-1
) and 50 times higher than
that of SU-8 nanocomposite cantilevers. With the high surface stress sensitiv-
ity and low noise levels it should be possible to detect surface stress values
down to 0.2 mN/m. h is performance can be attributed to the integration of
OFET as a strain sensor that consists of a very thin (~50 nm) strain sensitive
organic semiconductor layer pentacene in the channel region. h is capability
of detecting low surface stress makes the organic CantiFET a suitable candi-
date for many applications in biochemical sensor developments.
9.4
Polymer Microcantilever Sensors with Embedded
Al-doped ZnO Transistor
Organic CantiFET devices exhibited very high sensitivity, in addition to
other benei ts of embedded transistor coni guration for strain transduction.
