Biomedical Engineering Reference
In-Depth Information
UV Exposure with
appropriate dose
4
3
Pre-bake
5
Post-bake
Development in
SU-8 developer
Spin coat SU-8/CB
nanocomposite
2
6
Dispersion of
CB in SU-8
1
Sonicate in IPA to
remove CB residues
7
Sonication Probe
Sample
Controller
Ice water bath
Figure 9. 2
Microfabrication processing steps for SU-8/CB nanocomposite. Optical
micrographs of the SU-8/CB nanocomposite pattern before and at er i nal step of
sonication are shown.
patterned SU-8/CB samples had to be performed in order to remove the
carbon residue which is otherwise seen to be adsorbed all over the sample.
h e overview of these process steps along with optical micrograph of the
composite at intermediate steps is given in Figure 9.2. Nanocomposite
samples were coated with 10 nm of gold for subsequent analysis in scan-
ning electron microscope (SEM). h e SEM micrograph also coni rms the
uniform dispersion of CB nanoparticles in a SU-8 polymer matrix.
As prepared SU-8/CB nanocomposite thin i lms were mechani-
cally characterized using nanoindentation technique with a Hysitron
Triboscope. h is characterization was essential to understand whether
nanoparticle i ller loading would potentially change the Young's modu-
lus and hardness of SU-8 nanocomposite. Samples with varying CB con-
centrations were prepared on a silicon substrate. h e technique is based
on the analysis of elastic and plastic deformation in the material while
driving an indenter into the material whose mechanical characterization
has to be done. When the indenter is withdrawn from the material, the
elastic deformation is recovered. Indentations were carried out using a
Berkovich diamond indenter (E
i
= 1141 GPa and ν
i
= 0.07) with maxi-
mum load (P
max
) varying from 80 μN to 600 μN. Maximum loads applied
to the thin i lm samples were varied so that the indentation depth was
