Optimization of the production and insertion of 3-dimensional polyimide electrodes into rats Lab of Professor Patrick Rousche Hananeh 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

1 st 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

Final Electrode Roller

2 nd 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= mm/s Slow= mm/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 Medium Steel at Medium 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

GlassSteel Average Peak Height mN Standard Deviation 0.076mN Average Max Peak mN Standard Deviation 0.056mN

Agar gel and electrode

Average

AgarGlass and Steel Average Peak Height -.217mN Standard Deviation 0.062mN Average Peak Height mN Standard Deviation 0.076mN Average Max Peak mN 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 # 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.