Date of Submission
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Direct laser writing has, of late, become a widely popular technique for the
fabrication of microstructures, and in certain circumstances being preferred to
standard lithography techniques due to its dynamic nature in allowing for structure
formation without intermediate steps. In this field, a strong emphasis is placed on
multi-photon polymerisation, which allows for incredible feature precision. Singlephoton
polymerisation has begun to emerge, however, as a significantly less
expensive, and thus more accessible, alternative. One limiting factor to this
system, however, is its spatial indiscrimination in polymerisation, as reaction
initiation needs no more than one photon, and is thus not limited to high photon
population areas. Stemming from this complication, aside from a higher limit on
feature size due to focal limitations, is a phenomenon we have named the memory
effect. Though, in a single-photon system, significant polymerisation limits itself to
within a permissible range around the focal point to be able to form structures
below single micrometer dimensions, non-hardening oligomerisation seems to
occur in the outlier regions of the gaussian beam. This leads to increased
subsequent polymerisation in affected areas, enlarging neighbouring structures.
Our study sets out to define this effect and variables that may play a role in
lessening or even eliminating its consequences.
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Moura, Tiago, "Understanding Memory in Direct Laser Writing" (2013). Senior Projects Spring 2013. 332.