Biomedical Engineering Reference
In-Depth Information
is then solidified by baking at 120°C for 5 min.
Glass pillar arrays with high aspect ratio can
then be made after peeling off the PDMS mold.
Figure 12.20
a shows a side-view SEM image of
a templated sol-gel glass pillar array. The size and
depth of the glass pillars are reduced by
∼
10%
over those of the templating silicon pillars due to
the volume shrinkage during the solidification of
sol-gel precursor. The templated glass pillar
arrays exhibit excellent antireflective properties
over the whole visible spectrum (
Figure 12.20
b).
(a)
1
µ
m
(a)
(b)
5.0
Flat glass
Unitary ETPTA array
Binary ETPTA array
4.5
4.0
1.0
0.5
1
µ
m
0.0
400
500
600
700
800
Wavelength (nm)
(b)
5
FIGURE 12.19
(a) Cross-sectional SEM image of a
polymer moth-eye grating with binary structure. (b) Normal-
incidence specular reflectance spectra from a bare glass sub-
strate, a glass slide covered with a templated ETPTA binary
dimple-nipple array, and a glass slide coated with an ETPTA
unitary hemispherical nipple array. Adapted with permis-
sion from
J Phys Chem C
112
(2008), 17586-17591. Copyright
2008, American Chemical Society.
4
3
Experiment Simulation
Glass substrate
SOG pillar array
2
1
12.4.2 Templated Sol-Gel Glass Moth-
Eye Antireflection Coatings
0
The templated silicon pillars with high aspect
ratio (
Figure 12.11
d) can be used as second-gen-
eration templates to replicate sol-gel glass moth-
eye ARCs on transparent substrates
[105]
. A
PDMS mold is first cast over the silicon template
and then put on top of a sol-gel glass precursor
supported by a glass slide
[143]
. The precursor
400
500
600
700
800
Wavelength (nm)
FIGURE 12.20
(a) Cross-sectional SEM image of a tem-
plated sol-gel glass moth-eye pillar array. (b) Experimental
(solid) and RCWA-simulated (dotted) specular reflectance at
normal incidence from a flat glass substrate and a sol-gel
glass pillar array. Adapted from Ref.
105
.
