Biomedical Engineering Reference
In-Depth Information
Table 1.2 Piezoelectric Material Properties
Material
Y
(GPa)
σ
y
(MPa)
d
33
(pm/V)
k
33
(CV/Nm)
ε
/
ε
0
PZT-701
a
90
80
153
0.52
425
PZT-501
a
62
80
450
0.65
1950
PZT-507
a
62
80
820
0.75
4400
PMN-PT28
a
300
80
1700
0.90
5500
PMN-PT30
a
210
80
2200
0.94
7000
PZN-8%PT
b
8.3
80
2200
0.94
5100
a
Morgan Electro Ceramics plc.
b
Ritter et al. (2000)
maximum electric field of 100 MV/m (or a field of 100 V over 1
m)
gives a theoretical maximum value of 44 mJ/cm
3
, as shown in
Figure 1.4D
. A modest E of 30 MV/m produces 4 mJ/cm
3
, which can
be considered as a practical value.
μ
In summary, assuming a frequency of 1 Hz (similar to human walk-
ing, about one cycle per second), power (energy/time) calculations for
the electromagnetic transduction is limited to a maximum theoretical
value of 400 mW/cm
3
(4 mW/cm
3
practical value), piezoelectric genera-
tion can be as high as 343 mW/cm
3
(19 mW/cm
3
practical), while elec-
trostatic transduction is limited to 44 mW/cm
3
(4 mW/cm
3
practical),
see
Table 1.2
. These findings were also presented earlier by Roundy
(2003) in terms of energy as millijoules per cubic centimeter.
The transduction technology does not limit how much energy can
be harvested since over 1 mW of power can be produced by walking
from a 1 cm
3
generator (according to
Table 1.2
). Therefore, the next
question to answer is: How much energy is actually available and how
much can be scavenged?
