Toward the ultimate metal microelectrode.
The performance of metal microelectrodes for stimulating and recording neuronal action potentials depends on precise control of their geometrical, electrical and mechanical properties. We describe a combination of materials whose properties approach fundamental physical limitations on achievable performance and reproducible fabrication techniques that provide probes with very small dimensions. Pure iridium wire is electrolytically sharpened, vapor-coated with Parylene-C insulation and the tip exposed using an automatically steerable UV laser. Electrochemical activation of the iridium increases the capacitance of the metal-electrolyte interface so that the overall impedance in the relevant frequency band (100-10,000 Hz) is dominated by the access resistance of the surrounding tissues.
Loeb
G E
GE
Bio-Medical Engineering Unit, Queen's University, Kingston, Ont., Canada.
Peck
R A
RA
Martyniuk
J
J
D004553:Electric Conductivity; D017097:Electric Impedance; D004563:Electrochemistry / Q000295:instrumentation; D004594:Electrophysiology / Q000295:instrumentation*; D007495:Iridium; D008839:Microelectrodes; D011108:Polymers; D014992:Xylenes
D011108:Polymers; D014992:Xylenes; C011055:parylene; D007495:Iridium