3 research outputs found
Spirothiopyran-Based Reversibly Saturable Photoresist
Super-resolution
lithography holds the promise of achieving three-dimensional
(3D) nanopatterning at deep subwavelength resolutions with high throughput.
3D super-resolution lithography schemes demonstrated thus far have
all been serial in nature, primarily due to the lack of a photoresist
chemistry that not only couples a saturable reversibly switchable
reaction with a writing step but also has a low saturation threshold.
Here, we demonstrate that combining the reversible photoisomerization
of spirothiopyran with the thiol-Michael conjugate addition reaction
achieves the necessary photochemical characteristics. Green light
was found to saturate inhibition of the thiol-Michael addition writing
step at very low intensity thresholds. By formulating a spirothiopyran-functionalized
polyethylene glycol copolymer, we demonstrate spatial control over
cross-linking using inhibition by green light. Kinetics measurements
combined with photokinetic simulations show that interference lithography
on a spirothiopyran maleimide-based writing system using conventional
light sources (e.g., a 2 W green laser) should deliver super-resolution
features (∼45 nm wide lines) in thick films (tens of microns)
over large areas (hundreds of microns on a side). The unique combination
of reversible photochromic switching of spirothiopyran with the thiol-Michael
addition reaction marks an important step toward realizing a highly
parallelized 3D super-resolution writing system
Wetting Regimes for Residual-Layer-Free Transfer Molding at Micro- and Nanoscales
Transfer
molding offers a low-cost approach
to large-area fabrication of isolated structures in a variety of materials
when recessed features of the open-faced mold are filled without leaving
a residual layer on the plateaus of the mold. Considering both macroscale
dewetting and microscale capillary flow, a proposed map of wetting
regimes for blade meniscus coating provides a guide for achieving
discontinuous dewetting at maximum throughput. Dependence of meniscus
morphology on the azimuthal orientation of the stamp provides insight
into the dominant mechanisms for discontinuous dewetting of one-dimensional
(1-D) patterns. Critical meniscus velocity is measured and residual-layer-free
filling is demonstrated for 1-D patterned soft molds (stamps) with
periods ranging from 140 nm to 6 μm. Transfer of isolated lines,
and multilayer woodpile structures were achieved through plasma bonding.
These results are relevant to other roll-to-roll compatible processes
for scalable production of high-resolution structures across large
areas
Dynamic Imaging of Colloidal-Crystal Nanostructures at 200 Frames per Second
The dynamic noninvasive imaging of colloidal nanostructures has been precluded by the diffraction-limited resolution of (confocal) light microscopy. Using Fast Stimulated Emission Depletion (STED) microscopy, we demonstrate the ability to resolve the formation of a colloidal crystal (monolayer) from particles of 200 nm size, where the voids in the crystal are as small as 30 nm. With a temporal resolution of 5 ms, we exemplify the technique by visualizing the annealing of potential point defects during the formation of the colloidal crystal