Excursion of vibrating microelectrodes in tissue.

A vibrating microelectrode holder consisting of a support rod attached to the cone of a miniature loudspeaker facilitates electrode penetration into arterial wall tissue, eliminates surface dimpling, and relieves polarographic artifacts believed to be due to tissue compression. The longitudinal vibratory excursion of free microelectrode tips, measured with strobe illumination microscopy, varies from less than 0.9 to 137 micron depending on energizing voltage and frequency. Tissue penetration is achieved most effectively at the resonance frequency, about 200 Hz for the present system. Total tip excursion is not diminished when the electrode is penetrated into excised rabbit femoral artery, but tip motion relative to surrounding tissue is considerably attenuated because the arterial wall holds the electrode shaft rather firmly and follows its movements. This relative motion in tissue is only 2.7 +/- 0.8 micron at 200 Hz and 0.05 V and can be reduced further at higher frequencies without sacrificing the penetration advantages of the system. Thus under proper vibratory conditions microelectrodes can be easily inserted into the arterial wall with minimal tissue disturbance.