Biomedical Engineering Reference
In-Depth Information
1.00
50.0 nm
25.0 nm
0.75
0.0 nm
0.50
0.25
Nanoscope
Scan size
Setpoint
Scan rate
Number of samples
TM_AFM
1.000
m
2.000 V
3.052 Hz
512
µ
0
0
0.25
0.50
0.75
1.00
µ
m
Me, 001
FIGURE 3.48
An atomic force microscopy image taken on the surface electrode of a typical
muscle shown in figure 3.8. The scanned area is 1
m
2
. The brighter/darker area corresponds
to a peek/valley depth of 50 nm. The surface analysis image has a view angle set at 22
µ
°
.
Another fine tool to characterize the surface morphology of the IPMNC artificial
muscle is atomic force microscopy (AFM). Its capability to image the surface of the
IPMNC artificial muscle directly can provide detailed information with the resolution of
a few nanometers. Thus, we attempted to reveal the surface morphology of the IPMNC
artificial muscles using AFM. Figure 3.48 depicts an AFM image of an IPMNC sample.
Digital Instruments' AFM NanoScope IIIa was used. A tip (ultra levers) from
Park Scientific Instrument was utilized in an air-contact mode under low voltage.
As can be seen, the surface is characterized by a granular appearance of platinum
metal with a peak/valley depth of approximately 50 nm.
This granular nanoroughness seems to be responsible for producing a high level
of electric resistance but still provides a porous nature that allows water movement
in and out of the membrane. During the AFM study, it was also found that platinum
particles are dense and, to some extent, possess coagulated shapes.
The electrochemical deposition of silver (or copper) on top of the IPMNC muscle
was straightforward. It requires a rectifier and silver (or copper) solution. The rectifier
(MIDAS, pen type) controls the DC voltages and currents within appropriate ranges.
Careful approaches were taken to obtain a thin and uniform silver (or copper) layer.
Silver solution concentration, deposition time, and solution temperatures were varied
to obtain an optimized thickness of approximately 1-2
m.
Figure 3.49 shows a schematic diagram illustrating the silver deposition process
along with a typical x-ray spectrum taken for the silver surface. As can be seen in
the spectrum, pure silver peaks are apparent. The silver surface is much brighter and
smoother than that of the platinum-based IPMNC artificial muscle and shows a
typical silver-like color. As a result, the deposited silver reduces the surface resistance
of the IPMNC artificial muscle by a factor of approximately 10 (typically < 1
µ
Ω
/cm).
