Fabrication of Biosensor Chips - From Bioimaging to Biosensors: Noble Metal Nanoparticles in Biodetection - page 124

6.3.5 Nanoimprint Lithography

Nanoimprint lithography was proposed by Chou et al. [30] in 1996
for the fabrication of nanometer scale patterns. Since then, this
technique has been actively researched and extended to many
applications [31-36]. In principle, it uses compression molding to
create a thickness contrast pattern in a thin resist ilm carried on
a substrate, followed by anisotropic etching to transfer the pattern
through the entire resist thickness (shown in Fig. 6.14). The imprint
resist is typically a monomer or polymer formulation that is cured by
heat or UV light during the molding. To fabricate gratings, a master
grating fabricated by a method discussed in the above sections is
used as the mold during the imprinting to create replicates, which
could be made of material different from the master grating, rapidly
and cost effectively. In 2003 Yu et al . [37] adopted reactive ion
etching to transfer a grating patter to a silicon substrate; the SEM
image of the silicon gratings is shown in Fig. 6.13. On the other hand,
anisotropic wet etching was used by Jiao et al . [38] to transfer the
pattern to a gold ilm.

Figure 6.14 Process of nanoimprint lithography.

6.4 Manufacture of Optical Fiber Windows

Optical iber can be used as a iber optic sensor since light from
a source can be guided via the optical waveguide to areas for
testing physical or chemical characteristics, such as stress, strain,
temperature, refractive index, molecular concentration, etc. Since
these changes will result in changes to the optical characteristics,
analysis of changes in optical characteristics can be used to ind
physical or chemical quantity changes in the tested area. The basic
structure of the iber is shown in Fig. 6.15. Optical iber is essentially