Thin Film Microelectrodes (Part 1/7)

Danny Banks D.Banks at ee.surrey.ac.uk
Thu Oct 6 07:45:04 EST 1994


Neural - Electronics Interface.
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Danny Banks. <eep1db at ee.surrey.ac.uk> 

Copyright (c) 1994. 


Contents.

   Background. 
   The Microprobe. 
   Project Outline. 
   Experimental Investigation. 
   Computer Modelling. 

This document is a short version of a poster that has been on display in the
Department of Electronic & Electrical Enginnering, and the Department of
Mechanical Engineering, at the University of Surrey, since 1992. 



Background.

The human central nervous system (CNS) is highly complex, and also very
delicate. When injured it has relatively little ability to repair itself; a
notable example is the case of spinal cord injury. Electrical stimulation
techniques offer some hope of restoring partial function to paralysed limbs.
However, for all but the simplest applications it is necessary to provide some
sort of sensory feed-back. The patient usually has a fully operational array of
sensory receptors in the paralysed limb; signals from these are prevented from
reaching the brain by the damage to the spinal cord. However these signals may
be monitored by microelectronic devices implanted in the peripheral nervous
system (PNS); these signals may then be decoded, and used to modulate the
output of the stimulator to provide improved control of the stimulated muscle. 



The Microprobe.

The multi-microelectrode probe (microprobe) is a device that has been developed
mainly for CNS applications. However there are promising indications that
microprobes will be well suited to recording signals from peripheral nerve
trunks. 

The microprobe itself consists of one (or more) long thin shank, which is
inserted into the tissue under investigation, and a larger carrier area.
Recording electrode sites placed on the shank are connected to bonding pads on
the carrier area, for connection to external signal processing / display
equipment. 

The dimensions of the device vary with application; shank sizes of 2mm long,
100µm wide, and 20µm thick are fairly typical for CNS work. 

[IMAGE not available]


Project Outline.

The initial aims of this project are to: 

 1. determine the ability of microprobes to isolate signals from single fibres
   within peripheral nerve trunks; 
 2. determine how the geometry and positioning of the microprobe shank effects
   the recorded signals. 

These objectives are being pursued both experimentally, and by computer
modelling. 


Experimental: Microprobes will be used to record signals from peripheral nerves.
Their abilities to detect and isolate signals will be compared with other
devices / methods. A locust animal model is being used, since this simplifies
the experimental method. A number of different microprobe designs are being
fabricated in collaboration with Rutherford Appleton Laboratory and Southampton
University Microelectronics Centre. 

Computer Modelling: A finite element model of a microprobe shank inserted into a
peripheral nerve trunk containing an active fibre is being developed. 

A program to simulate an action potential propagating along a nerve fibre has
been written. The output from this program is being used as input to a finite
element analysis package, to analyse current flow, and voltage distribution,
around the fibre in a variety of situations. 


Danny Banks. 

<eep1db at ee.surrey.ac.uk> 



Copyright (c) D Banks, 1994.

The author grants permission to freely reproduce and distribute this work,
provided: 1) The work is reproduced in its entirety, and this copyright notice
is left intact; 2) The work is not reproduced, sold, re-sold, or distributed
for profit without the prior permission of the author; 3) Any use made of this
work is properly credited to the author. 


D.Banks at ee.surrey.ac.uk 
27 June 1994 

-- 
Danny Banks.				 		 eep1db at ee.surrey.ac.uk
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I'm *not* a mad scientist............................I'm an eccentric engineer.



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