61 research outputs found
Optimization of femtosecond laser processing in liquids
In this paper we analyze femtosecond laser processing of metals in liquids
searching for optimal conditions for predictable ablation. Incident laser
pulses are stretched or compressed, self-focused and scattered on bubbles and
on surface waves in the liquid environment. Influence of these effects on the
laser intensity distribution on the target surface is discussed and optimal
processing parameters are suggested
Formation of low- and high-spatial frequency laser-induced periodic surface structures (LIPSSs) in ALD-deposited MoS2
The formation of laser-induced periodic surface structures (LIPSSs) on the atomic layer-deposited (ALD) molybdenum disulfide (MoS2) upon femtosecond laser processing is studied experimentally. Laser-processing parameters such as average laser power and the scan speed at which the formation of the periodic nanostructures takes place are identified. Optical and scanning electron microscopy are applied to identify the parameter regions for the different LIPSS formations and transitions between them. High- and low-spatial frequency LIPSS (HSFL and LSFL) with two distinct periods λLSFL ≈ 1.1 μm and λHSFL ≈ 83 nm can be observed. The HSFL are dominating at higher and the LSFL at lower laser average powers. Formation of LIPSS is found to inhibit laser ablation at lower scan speeds
Pattern Formation in Slot-Die Coating
We experimentally study the occurrence of pattern formation during the
slot-die coating of low-viscosity nearly Newtonian liquids onto
Polyethylenterephthalat (PET)-substrates. In particular, it is demonstrated
that with increase of the coating speed a homogeneous coating becomes unstable
with respect to periodic stripe patterns. Thereby, depending on the liquid
viscosity, the stripes can be oriented parallel or perpendicular with respect
to the coating direction. Mixed states do also occur. The spatial period of
perpendicular [parallel] stripes increases [decrease] with the coating speed.
The dependence of the effect on various control parameters of slot-die coating
is investigated. Finally, a simple theoretical model based on the hydrodynamics
of thin films of partially wetting liquids is analysed. Comparing the results
to the experiments, conclusions are drawn regarding the acting instability and
pattern formation mechanisms.Comment: 24 pages, 10 figure
SPR DETECTION OF SINGLE NANO PARTICLES AND VIRUSES
Abstract Here we report a novel method for detection of single individual particles and viruses by means of surface plasmon assisted optical microscopy. The size of the studied objects may be at least one order of magnitude less than the wavelength of the light used for the imaging. This allows studying of nanoparticles and viruses in natural surrounding (enviroment) by means of cheap and well-developed visible-light sources. The signal reflected from the nanoparticle is enhanced due to excitation of the surface plasmon polariton waves. Combination with modern image-processing procedure allows automatic detection of nano-sized objects
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