Biomedical Engineering Reference
In-Depth Information
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Figure 9.7
(A) SU-8/CB resistor patterns on “V” shaped and “U” shaped cantilever
areas at er lithography process 4 (B)Photograph of the processed wafer at er the i nal
lithographic step showing arrays of polymer devices attached to the dummy substrate just
before the release(C) Arrays of polymer nanocomposite microcantilever device chips at er
release process (D) SEM image of one of the device chips containing 4 cantilevers.
etch (BOE). h e released device chips and SEM image of one of the fabri-
cated devices are also shown in Figures 9.7(C) and 9.7(D). h ese polymer
microcantilevers were about 3 μm thick and the SEM micrograph coni rms
the stress free nature of these free standing polymer nanocomposite struc-
tures achieved through an optimization of baking parameters for individ-
ual layers of SU-8 at dif erent levels of lithography.
9.2.3
Characterization of Polymer Nanocomposite Cantilevers
h e spring constant of the SU-8 nanocomposite microcantilever was
extracted using microcantilever beam bending technique using a nanoin-
denter, which provides high load and displacement measurement sen-
sitivity. Moreover the spring constant of the indenter (diamond) is very
high in comparison to the microcantilever structure. So this is a direct
and simple measurement technique, since one need not consider the case
of two springs in series as done in spring constant measurement using
standard AFM[40]. h e nanoindenter was used to apply load to the tip
of the microcantilever leading to the displacement of the microcantilever.
Using the indenter sot ware itself, the indenter was engaged with polymer
nanocomposite microcantilever and the indentation was performed. h e
load and unload segments showing the load and displacement as a func-
tion of time are shown in i gure 9.8(A). h e indentation was performed
