Biomedical Engineering Reference
In-Depth Information
600
(
a
)
100
80
500
60
40
20
0
400
SU-8
SU-8/ZnO (15%)
SU-8/ZnO (20%)
(
b
)
400 600
Wavelength (nm)
800
300
15 Wt%-480 mJcm
2
200
100
0
5
10
Wt % of ZnO
15
20
Figure 9.18
Optimized irradiation dose required for photo-patterning of the nano-
composite i lms as a function of various ZnO i ller concentration. Inset diagrams (a)
Transmission characteristics of the nanocompositethin i lms. (b) SEM image of the
patterned structures with optimized 15 wt % ZnO i ller concentration [32].
thin i lms, photopatternabilty is the key issue that needs to be optimized
in terms of inorganic i ller concentration and requires UV dose. It was
observed that SU-8 /ZnO nanocomposite retains their photopatternabilty
properties up to 15 wt % of ZnO nanoparticles and then subsequently
losses this property [32]. h e optimized UV dose for various W % of ZnO
nanoparticles are shown in Figure
9.18. h e loss of photopatternabilty prop-
erties can be explained with their transmission characteristics as shown
in inset Figure
9.18a. It could be seen from transmission characteristics
that transmittance of SU-8, which is originally more than 80% decreases
drastically with increasing ZnO nanoparticles content and reaches almost
0% as particles concentration reaches about 20 wt %. h e loss of litho-
graphic patterning properties of nanocomposite beyond 20 Wt % can be
due to high content of ZnO nanoparticles , which absorbs the major frac-
tions of UV dose and inhibits the cation photo polymerization reaction in
SU-8 [61-62].
9.5.1.2
Piezoelectric Response of Nanocomposite h in Films
h e other focus of research in SU-8 / ZnO nanocomposite thin i lms is to
evaluate their piezoelectric response for their applications in realization of
piezoelectric devices. Piezoforce microscopy (PFM) was used for probing
