Production of Centimeter-Scale
Gradient Patterns by Graded Elastomeric Tip Array
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Abstract
Large-area
patterned surfaces with chemical and/or morphological gradients have
significant applications in biology, chemistry, and materials science.
In this work, we developed a unique lithographic strategy to fabricate
2D and 3D gradient patterns with gradually varying feature size or
height over centimeter-scale areas by utilizing a large-area polydimethylsiloxane
(PDMS) tip array with programmable tip apex as a conformal photomask
in near-field photolithography. Meanwhile, a new strategy was developed
to create the PDMS tip array with graded apex size, which was employed
to fabricate gradient patterns with the lateral feature sizes changing
from sub-100 nm to several microns on one single substrate over macroscopic
(square centimeter) areas. Furthermore, 3D gradient patterns with
spatially varying feature height were enabled by employing gradient
exposure dose. The formation of gradient feature size was ascribed
either to gradient contact areas between tips and substrates or to
exposure dose gradient. This lithography strategy combines the advantages
of a wide range of feature sizes, simplicity, high-throughput, low-cost
and diversified feature shapes, making it a facile and flexible approach
to manufacture various functional gradient structures