Abstract
Holographic lithography is a convenient, inexpensive technique to fabricate
large-area, periodic biofunctional templates such as antireflection and superhydrophobic
surfaces. As opposed to two-beam interference (TBI), which produces grating patterns,
interference of three or more beams can create multifarious patterns of symmetry, which
have broader range of functions. However, as the number of beams used increases, the
configuration gets more complicated, and thus possibly incurs more errors of alignment.
To avoid the issue, we employed the technique of multi-exposure of two-beam interference
to fabricate two-dimensional periodic structures and quasi-periodic structures. The
theoretical simulation of 2n-beam interference (n is a positive integer) and n
exposures of TBI was compared to validate that patterns made by 2n-beam interference
could also be made by n exposures of TBI. Structures with symmetry of different folds
were demonstrated not only on the negative photoresist SU-8 based on an add-type
fabrication approach but also directly on the surface of the infrared window material
zinc sulfide (ZnS) through a subtract-type fabrication approach. A transmittance of more
than 90% and a water contact angle of 145° were obtained by three exposures of
two-beam interference, and a transmittance of 80% as well as a water contact angle of
126° by ablation of nine exposures of TBI on ZnS substrate.
© 2012 IEEE
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