EFFECT OF SMOOTH, POROUS AND FRACTAL SURFACE-STRUCTURE ON THE PROPERTIES OF AN INTERFACE

Recently, biomaterials research has focused on the creation of new mat erials. Mixing or doping of well-tried materials should aim to result in new physical or chemical properties, better tissue tolerability and improved long-term stability. We present another way of improving per formance: the application of new technologies to well-known materials. The surface structure of a coating depends on the deposition techniqu e. Hence, the transfer of, for example, sputtering technology to biote chnology may solve current problems with well-tried materials. This pa per reports the influence of surface structure and area on the propert ies of pacemaker electrodes. Smooth electrodes were compared with poro us electrodes produced by sintering and with fractal electrodes result ing from physical vapour deposition of iridium or titanium nitride. Mi crographs revealed a slight enlargement of the surface area by sinteri ng and an enormous enlargement with fractal coating. Analysis of elect rochemical properties proved the advantages of fractal coating: the im pedance spectra exhibited incomparable low impedances for frequencies down to 1 Hz and no afterpotentials could be detected. Clinical result s confirmed the superiority of fractal electrodes. The stimulation thr esholds were significantly reduced, P-and R-wave amplitudes were incre ased, and ventricular evoked responses and monophasic action potential s were able to be measured with clarity unknown so far.