Planar off-chip microelectrode for the electrophysiological measurement of small biological cells

We have developed a planar, off-chip microelectrode with a very sharp tip (400 nm tip end width) for the measurement of biological cell membrane potentials. The electrode consists of a tungsten electrode on the silicon dioxide support structure, a parylene-N conformal coating for electrical insulation, and a silicon base to facilitate mounting of the probe on the end effector of a micromanipulator. The parylene-N layer at the end of microelectrode tip is opened to allow electrical communication between the biological cell and the tungsten electrode by femtosecond laser ablation.