We present recent advancements in two-photon grayscale lithography (2GL®). In contrast to one-photon grayscale lithography, for 2GL®, the exposed volume pixel is strongly confined to the vicinity of the laser focus allowing for a truly 3-dimensional dose control with very high spatial resolution. Discrete and accurate steps, as well as essentially continuous topographies, can be printed with increased throughput, on any substrate, and without the need for additional lithography steps or mask fabrication. We update on throughput and quality levels of the method. As demonstrators, we fabricate and characterize optics masters for replication technologies like nanoimprint lithography.
Direct laser writing via two-photon absorption allows the fabrication of three-dimensional dielectric structures with submicron
resolution by tightly focusing ultrashort laser pulses into a photo-sensitive material with a high-resolution
microscope objective and scanning the laser focus relative to the material. Woodpile photonic crystals fabricated with
this method show a characteristic dip in transmission at near-infrared wavelengths. The spectral position of this
transmission dip scales with the grating period of the fabricated crystals. Metallo-dielectric structures can be obtained by
first fabricating dielectric templates with direct laser writing and subsequently coating the templates with a thin
conformal metal film by electroless plating. Contiguous and conducting silver films can be deposited even on convoluted
3D geometries.
The interference of three coherent laser beams of a HeCd-laser with a wavelength of 325 nm was used to create a
periodic intensity distribution into the photo-resist AZ4562. The beam configuration for the laser beam interference was
carefully chosen, so that well defined patterns of two-dimensional periodicity were generated in the photo-resist.
Moulding tools were fabricated from the generated nano-structures via electroforming processes, allowing for a fast
replication of the nano-structured surfaces via hot embossing. Hot embossed polymers were used to increase the
effective surface of micro-fluidic devices like e.g. Polymerase-Chain-Reaction(PCR)-chips. The Nano-structured
surfaces were characterized concerning their contact angles when wetted with de-ionized water. It was found that the
nano-structures influenced the wetting behaviour of micro-fluidic chip surfaces clearly, especially Polypropylene (PP)
surfaces showed a superhydrophobic behaviour.
We present the fundamental concept and experimental results of a new optical sensor structure based on a 1D photonic crystal consisting of a polymer light waveguide, a cladding layer and a nanostructured gold layer. The polysiloxane layers are deposited by spin-coating and dip-coating, respectively. The gold nanostructure is deposited by DCmagnetron sputtering and structured by UV-laser lithography. The gold nanowires have a period of about 400 nm and cover an area of 5×5 mm2. This thin flexible structure shows high sensitivity to inclination and strain. Our method enables the fabrication of a new sensor for non-conducting measurement of strain, force, torque and angle.
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