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Synthesis of Micropillar Arrays via Photopolymerization: An in Situ Study of Light-Induced Formation, Growth Kinetics, and the Influence of Oxygen Inhibition
journal contribution
posted on 2017-07-25, 14:04 authored by Fu Hao Chen, Shreyas Pathreeker, Saeid Biria, Ian D. HoseinWe report a study
on the growth kinetics and resultant structures
of arrays of pillars in photo-cross-linkable films during irradiation
with a periodic array of microscale optical beams under ambient conditions.
The optical beams experience a self-focusing nonlinearity owing to
the photopolymerization-induced changes in refractive index, thereby
concentrating light and driving the concurrent, parallel growth of
microscale pillars along their path length. We demonstrate control
over the pillar spacing and pillar height with the irradiation intensity,
film thickness, and the size and spacing of the optical beams. The
growth of individual pillars in a periodic array arises from the combination
of intense irradiation in the beam regions and oxygen inhibition afforded
by the open, ambient conditions under which growth is carried out.
We propose a kinetic model for pillar growth that includes free-radical
generation and oxygen inhibition in thick films of photoinitiated
media in order to interpret the experimental results. The model effectively
correlates micropillar array structure to the oxygen inhibition effects.
This approach of growing micropillar arrays through photopolymerization
is straightforward and scalable and opens opportunities for the design
of textured surfaces for applications.