2 research outputs found
Local Modification of the Microstructure and Electrical Properties of Multifunctional Au–YSZ Nanocomposite Thin Films by Laser Interference Patterning
Nanocomposite films consisting of
gold nanoparticles embedded in
an yttria-stabilized zirconia matrix (Au–YSZ) have been synthesized
with different gold loadings by reactive magnetron sputtering followed
by ex situ annealing in air or laser interference patterning (LIP)
treatment. It is shown that the electrical conductivity of the nanocomposite
films can be modified to a large extent by changing the gold loading,
by thermal annealing, or by LIP. The structural and microstructural
analyses evidenced the segregation of metallic gold in crystalline
form for all synthesis conditions and treatments applied. Thermal
annealing above 400 °C is observed to trigger the growth of pre-existing
nanoparticles in the volume of the films. Moreover, pronounced segregation
of gold to the film surface is observed for Au/(Au + Zr + Y) ratios
above 0.40, which may prevent the use of thermal annealing to functionalize
gold-rich Au–YSZ coatings. In contrast, significant modifications
of the microstructure were detected within the interference spot (spot
size close to 2 × 2 mm) of LIP treatments only for the regions
corresponding to constructive interference. As a consequence, besides
its already demonstrated ability to modify the friction behavior of
Au–YSZ films, the LIP treatment enables local tailoring of
their electrical resistivity. The combination of these characteristics
can be of great interest for sliding electrical contacts
Surface Modification of Brass via Ultrashort Pulsed Direct Laser Interference Patterning and Its Effect on Bacteria-Substrate Interaction
In recent decades, antibiotic resistance has become a
crucial challenge
for human health. One potential solution to this problem is the use
of antibacterial surfaces, i.e., copper and copper alloys. This study
investigates the antibacterial properties of brass that underwent
topographic surface functionalization via ultrashort pulsed direct
laser interference patterning. Periodic line-like patterns in the
scale range of single bacterial cells were created on brass with a
37% zinc content to enhance the contact area for rod-shaped Escherichia coli (E. coli). Although the topography facilitates attachment of bacteria to
the surface, reduced killing rates for E. coli are
observed. In parallel, a high-resolution methodical approach was employed
to explore the impact of laser-induced topographical and chemical
modifications on the antibacterial properties. The findings reveal
the underlying role of the chemical modification concerning the antimicrobial
efficiency of the Cu-based alloy within the superficial layers of
a few hundred nanometers. Overall, this study provides valuable insight
into the effect of alloy composition on targeted laser processing
for antimicrobial Cu-surfaces, which facilitates the thorough development
and optimization of the process concerning antimicrobial applications