Biomedical Engineering Reference
In-Depth Information
F
C
2
H
2
/
F
Ar
=1.2
F
C
2
H
2
/
F
Ar
=1.0
F
C
2
H
2
/
F
Ar
=0.8
F
C
2
H
2
/
F
Ar
=0.6
F
C
2
H
2
/
F
Ar
=0.4
Graphite
2000
1600
1200
800
400
Raman shift (cm
−
1
)
FIGURE 19.32
Raman spectra of DLC fi lms fabricated at different
F
C
2
H
2
/
F
Ar
ratios. (From Chen, J.Y. et al.,
Surf. Coating Tech.
, 156, 289, 2002. With permission.)
300
2.0
(b)
(a)
1.9
250
1.8
200
1.7
150
1.6
1.5
100
1.4
50
1.3
1.2
0
0.4
0.6
0.8
1.0
1.2
0.4
0.6
0.8
1.0
1.2
Flow ratio
Flow ratio
FIGURE 19.33
Effects of the
F
C
2
H
2
/
F
Ar
fl ow ratios on the intensity ratio of the D-band to G-band (a) and
platelet counts (b). (From Chen, J.Y. et al.,
Surf. Coating Tech.
, 156, 289, 2002. With permission.)
spectra indicate that smaller
F
C
2
H
2
/
F
Ar
fl ow ratios weaken the formation of DLC fi lms with more
fourfold coordinate bonds. That is, the sp
3
bond content is reduced at smaller
F
C
2
H
2
/
F
Ar
fl ow ratios.
Both the peak width and
I
D
/
I
G
intensity ratio vary depending on the structure of the DLC fi lms.
Platelet adhesion tests are conducted on the DLC fi lm surface. After incubation in the
platelet-rich plasma (PRP) for 20 min, the number of adherent platelets on the DLC fi lm surface
fi rst increases, and then decreases with increasing
F
C
2
H
2
/
F
Ar
fl ow ratios. The platelet count is high-
est at a
F
C
2
H
2
/
F
Ar
fl ow ratio of about 0.8. After 3 h of incubation, the adherent platelets are too
numerous to count. The amount of platelets on sample prepared under
F
C
2
H
2
/
F
Ar
fl ow ratio of 0.8 is
the highest, and the accumulation of platelets is also most serious as manifested by several platelets
interconnecting to form aggregation. In addition, serious pseudopodium of the adhered platelets is
also observed serious on this sample.
Figure 19.33 displays the relationship between the Raman D-band to G-band intensity ratios
and the platelet quantity for different
F
C
2
H
2
/
F
Ar
fl ow ratios. It can be readily observed that these two
parameters agree well with each other. That is, both increase fi rst and then decrease with increasing
F
C
2
H
2
/
F
Ar
fl ow ratios. The largest value is observed at a
F
C
2
H
2
/
F
Ar
fl ow ratio of 0.8-1.0. Taking into
