Stretchable and compliant electrodes on polydimethylsiloxane (PDMS) are efficiently fabricated by the implantation of neutral metallic clusters aerodynamically accelerated by a supersonic expansion. The production of these nanocomposite electrodes avoids any charging or carbonization of PDMS and the electrodes can withstand many deformation cycles, decreasing their resistance upon cyclical stretching. Micrometric patterns can be simply fabricated by stencil mask patterning.

We fabricated highly adherent and electrically conductive micropatterns on SU-8 by supersonic cluster beam deposition (SCBD). This technique is based on the acceleration of neutral metallic nanoparticles produced in the gas phase. The kinetic energy acquired by the nanoparticles allows implantation in a SU-8 layer, thus producing a metal-polymer nanocomposite thin layer. The nanocomposite shows ohmic electrical conduction and it can also be used as an adhesion layer for further metallization with a metallic overlayer. We characterized the electrical conduction, adhesion and biocompatibility of microdevices obtained by SCBD on SU-8 demonstrating the compatibility of our approach with standard lift off technology on 4'' wafer. A self-standing and flexible Micro Electrode Array has been produced. Cytological tests with neuronal cell lines demonstrated an improved cell growth and a spontaneous confinement of cells on the nanocomposite layer.

No abstract

We studied the excitation dynamics and the photoluminescence spectra in polymeric matrix implanted with metallic nanoparticles. A supersonic beam of gold nanoparticles (sizes 2-7 nm) was generated by using a Pulsed Microplasma Cluster Source (PMCS). The nanoparticles were implanted in a thin polyfluorene film (thickness around 100 nm) spin coated on a PMMA (poly methyl methacrilate) substrate. We performed photoluminescence and pump-probe measurements using a Ti:Sapphire amplified laser system, the excitation pump pulse was centered at 400 nm with a 150 fs time duration. The experimental results show a suppression of the amplified spontaneous emission from the polyfluorene (PFO) film due to the presence of the implanted nanoparticles. The transient transmission spectra revealed the presence of a photoinduced absorption band due to the nanoparticles which overlaps with the stimulated emission band from the PFO, hindering the possibility of having amplified spontaneous emission. These results demonstrate the possibility of a local nanotailoring of the polymeric photophysics.

Electrical conduction in Fe, Pd, Nb, W and Mo cluster-assembled films was investigated in-situ, during their growth by supersonic cluster beam deposition. We observed for clusterassembled films resistivity values several orders of magnitude larger than corresponding bulk, as well as an increase of resistivity by increasing the film thickness, in contrast to the behaviour of atom-assembled metallic films. This suggests that nanoscale morphology arising by growth dynamics of cluster-assembled films, such as the minimal cluster-cluster interconnection and the evolution of surface roughness with thickness, may play a crucial role in the observed behaviour. Theoretical models based on non-isotropic 3D distributions of clusters into the film would help for a deeper understanding of the behaviour of cluster-assembled films compared to atomassembled ones. Benefits are expected in the technological field of devices performing electrical read-out on active nanostructured layers, as in the case of chemoresistive sensors.