Biomedical Engineering Reference
In-Depth Information
transport healing and repairing materials and chemicals to any location in the body
or to the surfaces and skins of the body, and many more. A first-order analytical
model for such nanocomposites can be stated using linear irreversible thermody-
namics with fluxes such as a current density,
J
, and the flux of water + ions and
chemicals,
Q.
The conjugated forces include the electric field,
E
, and the pressure
gradient, -
∇
p
. The resulting equations are equations 2.2 and 2.3.
2.2.8
N
EAR
-DC M
ECHANICAL
S
ENSING
, T
RANSDUCTION
,
AND
E
NERGY
-H
ARVESTING
C
APABILITIES
OF
IPMNC
S
IN
F
LEXING
, B
ENDING
,
AND
C
OMPRESSION
M
ODES
As discussed before, IPMNCs have excellent sensing capability in flexing and com-
pression. Further, as will be discussed in detail in chapter 7 of this topic, IPMNCs'
active elements not only are capable of sensing rather high frequencies but also are
capable of near-DC dynamic sensing and acceleration measurement, as shown in figure
2.37. In this sense, they are far superior to piezoelectric materials, which are only
suitable for high-frequency sensing while, for low-frequency or near-DC sensing,
piezoresistors are generally used. Thus, they span the whole range of frequencies for
dynamic sensing and have wide bandwidth. These issues will be detailed in chapter 7.
Power harvesting capabilities of IPMNCs are also related to near-DC or even
high-frequency sensing and transduction capabilities of IPMNCs. Figure 2.38 depicts
a typical near-DC voltage and current production of IPMNC cantilevers. The exper-
imental result shows that almost a linear relationship exists between the voltage
output and the imposed displacement of the tip of the IMPC sensor.
IPMNC sheets can also generate power under normal pressure. Thin sheets of
IPMNC were stacked and subjected to normal pressure and normal impacts and were
5
4
3
2
1
0
0 0 0 0 0 0 0 0 0 0
Deformed angle relative to standing position (degree)
FIGURE 2.37
Near-DC sensing data in terms of produced voltages, ∆
E
, versus displacement.
Note that the displacement is shown in terms of the deformed angle relative to standing
position in degree in a cantilever configuration. The dimension of the sample sensor is 5 ×
25 × 0.12 mm.
