Coatings continued porosity

Continuous Pt films at the surface of porous silicon cannot be applicable as catalytic coats for fuel cells electrodes. Quite the contrary, Pt coats should save its porosity to allow an easy penetration of gaseous iuel and to have the effective surface area as high as possible. So, the layers of electrodeposited Pt of about 100 nm in thickness, as illustrated in Fig. Ic, are optimal catalytic Pt films for micro fuel cell electrodes. 

Coated fibers are generally characterized in terms of coating uniformity, continuity, thickness and composition. Scanning electron microscopy can be used for the first three types of characterization, while X-ray powder diffraction and/or transmission electron microscopy (+ EDS/EELS) can provide compositional information [194]. The residual porosity within the coating is also considered, particularly if a hermetic coating is needed for environmental protection of the fiber. 

In this way, a stimulation electrode is formed where a porous coating of an insulating parylene film is partially deposited. The porosity of the film is continuously decreasing with the film thickness. This issue allows precisely defined windows in the parylene film and high reproducibility in the production of the stimulation electrodes. 

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