Biomedical Engineering Reference
In-Depth Information
Fig. 4.43.
A schematic of the regeneration electrode
to prosthetic devices, such as the control of artificial limbs for amputees or
the control of an artificial heart by information from the autonomic nerve.
The development of the regeneration electrode has been undertaken using
many kinds of materials since the 1960s. After Matsuo reported their fabri-
cation on a silicon substrate, many kinds of silicon regeneration electrode
have been proposed. Kovacs reported a micromachined regeneration electrode
[164]. Most of the recent successful reports of measurements of nerve signals
by regeneration electrodes have been based on silicon substrates. However,
the weakness of the substrate becomes a problem when the implantation
procedure is put to real use.
We have designed and fabricated a flexible regeneration microelectrode on
a polyimide substrate using ordinary Flexible Printed Circuit (FPC) techno-
logy [165]. Polyimide has a good biocompatibility and is easily workable by
an excimer laser, but the greatest advantage of polyimide is its flexibility,
which aids physical compatibility during long-term implantation.
The schematic of the flexible regeneration microelectrode that we fabri-
cated is shown in Fig. 4.43. The electrode was composed of three layers. A
metal electrode pattern layer was sandwiched between two polyimide layers.
Silicone tubes fixed the nerve stumps to the electrode. The other terminal of
the electrode was connected to the connector during signal recording.
We implanted the electrode between the ends of the surgically severed
sciatic nerve of rats under pentobarbital anesthesia. We cut the nerve bundle,
inserted the nerve ends into each of the silicon tubes and fixed them with
one 10-0 nylon suture at each end. It was possible to record the spontaneous
action potential from the regenerating nerves.
At present, we are improving the electrode. We are using Pt as the metal
layer and the polyimide layer is thinner (approximately 8
m).
μ
Summary of Microelectrodes.
To summarize the microelectrode tech-
nology mentioned above, it is true that the technology has been developed
remarkably, especially with regard to the number of the channels (electrodes)
and the size of the whole electrodes, as compared with the handmade elec-
