This is a sample.
60 electrodes are aligned in an 8 x 8 grid with interelectrode distances of 200 m. 
The platinum electrodes are approx. 50 m high and have a diameter of about 40 m at the base, ending in a fine small tip. 
Tracks and contact pads are also made of platinum; insulation material is SU-8.

Recording of activity from a Hippocampal slice on a 3d MEA.