Nanotechnology-Enabled Sensors

192 Chapter 4: Nano Fabrication and Patterning Techniques
SF-NIL was first developed by Willson and coworkers. 82 Instead of using
a thermally curable resists (as in T-NIL), SF-NIL utilizes a UV curable
resist on the sample substrate. The mold is comprised of a UV transparent
material. After the mold and the substrate are pressed against each other,
the resist is cured with UV light. An example shown in Fig. 4.44. In this
example, polydimethylsiloxane (PDMS) photoresist has been used. PDMS
is a “soft” material which is highly suited for nano-imprinting technology.
Photoresist pattern PDMS
Silicon Silicon
Silicon
(a) (b)
(c)
Fig. 4.44 An example of the SF-NIL procedure with PDMS as the UV curable resist.
Using this method, patterns of biological origin can be replicated. As
can be seen in Fig. 4.45 the wing of a cicada (an insect) has been molded
in PDMS with the SF-NIL technique.
Fig. 4.45 Cicada wing (left) and its mold created by SF-NIL (right)
As shown in Fig. 4.46, the nanosized features in the cicada wigs surface
have been successfully replicated with this technique.