Wireless Sciatic Nerve Stimulator

1
Wireless Sciatic Nerve Stimulator

• Final Presentation
• Team 3
• Anne Wilson
• Tom Richner
• Justin Horowitz

2
Need

• Current Moran lab device must connect to external
  stimulator
• Only one stimulation opportunity
• Must be twisted during implantation
• Damage to connector pads
• Damage to regenerating nerve, surrounding tissue

3
Implantable, wireless sciatic nerve stimulator

• Sieve electrode inside nerve conduit
• Powered and controlled by outside signal
• Multiple stimulation channels
• Gradation of stimulus intensity

4
Polyimide Circuit BoardFoldingTracks, viaholes,
and surface mount tabs printed on one side
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Polyimide Circuit Board and Silicone Nerve Conduit

• Nerve conduit will have gold wire wrapped around
  it
• Sieve electrode inserted into slit in nerve
  conduit
• Rectangular portion of circuit board wrapped
  around nerve conduit

6
Circuit Board Dimensions
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Circuit Diagram
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Source Capacitor Charging
1 MHz, 4V AC in.
6 MHz, 4V AC in.
The power source capacitor charges in less than 1
µs from stimulation onset even under maximum
load.
9
Frequency Discrimination
As seen in an AC sweep, the high and low pass
filters cutoffs were designed such that they can
discriminate between a 1 or 6 MHz signal by their
relative amplitudes.
10
Power Frequency Response and Heat
Power consumption at maximum load. 239 µcal/s 1
mW. Therefore, about 15.5mcal/s dissipated
even if all the energy goes into a single gram of
water, it only goes up 0.0015 C per second of
maximum draw. Heat is irrelevant.
11
Inductor/Transformer Resistivity
Wire Silicone Tubing
Gold wire resistivity from industry trade group
http//www.gold.org/discover/sci_indu/properties/i
ndex.html
12
Gradation of Stimulus D-to-A converter
13
DesignSafe summary

• Mitigation of electrical risks no long-term
  charge storage, low current and voltage levels,
  voltage controlled output
• Minimize surgical risks well trained,
  experienced doctor
• Avoid rat scratches, bites, etc. through animal
  training, PPE

14
Photolithography

• Printing the Circuit Board

• Multiple photomasks (gold, polyimide) so multiple
  cycles
• Light removes areas of protective photoresist so
  that chemical digestion can occur on the exposed
  areas
• Chemical digestion carves mask pattern into
  substrate material

15
Manufacturing Process Overview

• Wafers hold multiple devices
• Photolithography- print only wiring
• Connector pads to attach circuit elements
• Wrap polyimide around
• mandrill and secure
• Use wire bonding to
• attach R, C, diodes,
• microcontroller

16
Part List
17
Conclusions

• Successfully designed a prototype
• Microcontroller vs. ASIC
• Manufacturing process more complicated
• No IP will only be used in an academic lab
• Size restrictions
• Number of I/O leads on microcontroller
• Higher order filters require too many R and C
• Full wave rectifier vs. half wave rectifier

18
Questions?