Iridium oxohydroxide thin coatings have been prepared by a dynamic oxidation electrodeposition method from complex oxalate solutions that induce template effects in the final coating at the nanoscale. The preparation method induces the formation of a oxohydroxide with reproducible stoichiometry and sponge-like quasiamorphous open structure, high ionic mobility, and significant behavior as compared with other reported iridium oxides as derived from X-ray diffraction, XPS, and TGA. Reproducible mixed valence states are also observed and a local rutile structure that allows ion exchange and facile redox changes. Rather significant is the large affinity for organic compounds observed and the behavior as substrate for cell culture, the best observed to date. Optimal cell response seems to be related to such open structure, which suggests this coating as ideal for devices implanted in the nervous system.

Innovative neurostimulation therapies require improved electrode materials, such as poly(3,4-ethylenedioxythiophene) (PEDOT) polymers or IrO mixed ionic-electronic conductors and better understanding of how their electrochemistry influences nerve growth. Amphibian neurons growing on transparent films of electronic (metal) conductors and electronic-ionic conductors (polymers and semiconducting oxides) are monitored. Materials are not connected directly to the power supply, but a dipole is created wirelessly within them by electrodes connected to the culture medium in which they are immersed. Without electrical stimulation neurons grow on gold, platinum, PEDOT-polystyrene sulfonate (PEDOT-PSS), IrO , and mixed oxide (Ir-Ti)O , but growth is not related to surface texture or hydrophilicity. Stimulation induces a dipole in all conductive materials, but neurons grow differently on electronic conductors and mixed-valence mixed-ionic conductors. Stimulation slows, but steers neurite extension on gold but not on platinum. The rate and direction of neurite growth on PEDOT-PSS resemble that on glass, but on IrO and (Ir-Ti)O neurites grow faster and in random directions. This suggests electrochemical changes induced in these materials control growth speed and direction selectively. Evidence that the electric dipole induced in conductive material controls nerve growth will impact electrotherapies exploiting wireless stimulation of implanted material arrays, even where transparency is required.

a b s t r a c tA Li 1.5 [Al 0.5 Ge 1.5 (PO 4 ) 3 ] glass composition was subjected to several crystallization treatments to obtain glass-ceramics with controlled microstructures. The glass transition (T g ), crystallization onset (T x ) and melting (T m ) temperatures of the parent glass were characterized by differential scanning calorimetry (DSC). The glass has a reduced glass transition temperature T gr = T g /T m = 0.57 indicating the possibility of internal nucleation. This assumption was corroborated by the similar DSC crystallization peaks from monolithic and powder samples. The temperature of the maximum nucleation rate was estimated by DSC. Different microstructures were produced by double heat treatments, in which crystal nucleation was processed at the estimated temperature of maximum nucleation rate for different lengths of time. Crystals were subsequently grown at an intermediate temperature between T g and T x . Single phase glass-ceramics with Nasicon structures and grain sizes ranging from 220 nm to 8 lmwerethensynthesizedand the influence of the microstructure on the electrical conductivity was analysed. The results showed that the larger the average grain size, the higher the electrical conductivity. Controlled glass crystallization allowed for the synthesis of glass-ceramics with fine microstructures and higher electrical conductivity than those of ceramics with the same composition obtained by the classical sintering route and reported in literature.