Optimization of the production and insertion of 3-dimensional polyimide electrodes into ratsLab of Professor Patrick RouscheHananeh Esmailbeigi

Daniela Aizpitarte

Overall Picture

• Create a 3d electrode• Will be filled with neurotrophic factors to increase neuron growth in the region• Goal is to decrease noise and measure strong long term signals• Has many uses for neural prosthetics•Made of polyimide-a very flexible polymer

1st Project: Creating a rolling system

• Current system is time consuming• Requirements:

• Steady the two needles• Keep the electrode perpendicular to the needle• Be able to roll electrodes quickly• Allow the needles to be removed after use

Image from www.sanimedtech.com

Final Electrode Roller

2nd Project: Implantation

• A hypodermic needle needs to accompany the electrode

• Rolled tip is too blunt to penetrate the pia without buckling

• Needs to be simple to make• Can’t increase damage to the surrounding tissue

Injection Needle Idea• How it works:

• The two halves are gently separated• One half is pulled up at a time•Made of stainless steel

• Advantages:• Simple construction

• Disadvantages:•Hard to control

Final Inserter Design• Glass capillary tube

4mm long• Tip sanded down to a

45 degree angle• Success when used in

surgery

Force of Implantation

• A glass capillary tube at a 45 degree angle was sanded down and inserted 4mm into 0.5% agar gel

• Three different relatives speeds were tested: fast, medium, slow

• Fast= 5-7mm/s• Medium=2.5-3.5mm/s• Slow=0.3-0.5mm/s

Fast Trials

Medium Trials

Conclusions• Inserting faster exerts

less force (speed dependent)

• Diameter had to be taken into account

• Steel and glass are of the same hardness, and should exert the same force

Average peak (mN)

Standard Deviation (mN)

Fast 7.37 0.97

Medium 10.5 1.39

Steel at Medium

7.63 1.03

Per surface area of 1.2mm diameter circle

Electrode sticking test: Water

Water dish test

Conclusions

•Water is easily lifted up the electrode and gives varying measurements

•Force changes on the order of 0.01 mN▫Too small to have great significance

Wet electrode testing: Steel and glass

Visual Comparison

Glass Steel

Average Peak Height

-0.158mN

Standard Deviation

0.076mN

Average Max Peak

-0.160mN

Standard Deviation

0.056mN

Agar gel and electrode

Average

Agar Glass and Steel

Average Peak Height

-.217mN

Standard Deviation

0.062mN

Average Peak Height

-0.158mN

Standard Deviation

0.076mN

Average Max Peak

-0.160mN

Standard Deviation

0.056mN

Conclusion

•The effect of water on the electrode is minimal

•The electrode prefers the agar over glass capillary tube▫Reason why the surgery worked▫Actually pulls away the agar gel

•Electrode rolling technique overall didn’t work better than hand rolling

Acknowledgments

I would like to thank the financial support from the EEC-NSF Grant # 0755115 for funding the REU program. Also, I would like to thank Professor Rousche and the rest of the REU program for giving me this project.