Sub-diffraction optical lithography beyond acrylates

Description

Stimulated emission depletion (STED) broke the diffraction limit of resolution in fluorescence
microscopy and it has been proposed thala STED-confined excitation volume should be equally
applicable to spatially control chemical reactions on the nanometre scale.l Meanwhile, this
prediction has been experimentally realized using free radical polymerization of mostly
(meth)acrylates.2-a Recent progress has been made in finding an optically depletable starter
which shows only low autofluorescence in the visible spectrum, so that it can be used for
biomedical applications without interfering with fluorescent tags.s Using the STED-inspired
concept of transient-state absorption depletion (TAD), three dimensional structures of 40 nm
size in lateral and axial direction can be realized, which corresponds to 1/20 of the excitation
wavelength.s
However, this concept was restricted to free radical polymerization for a long time. Only very
recently, it has been transferred to optical nanolithography comprising cationic or oxidative
polymerizations. For instance, we found a photosensitizer/initiator couple with which STED-
inspired writing of sub-100 nm wide epoxide lines became possible.6'7 Besides, we also
managed to write sub-100 nm wide lines of n-conjugated polymers, applying TAD lithography
to the oxidative polymerization of 3,4-ethylendioxythiophen (EDOT).8 Such n-conjugated
structures are particularly intriguing because they hold promise for sub-diffractional organic
electronic devices.

Period	2025
Event title	Linz Winter Workshop 2025
Event type	Conference
Location	4040 LinzShow on map