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Erika A. Parra EE235 4/9/07

“Detection , Stimulation, and Inhibition of Neuronal Signals with High Density Nanowire Transistor Arrays” By Fernando Patolsky Science: August 2006. Erika A. Parra EE235 4/9/07. Outline. Neuron Terminology NW-FET & Neurons Device Fabrication Results Signal Propagation Signal Blocking

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Erika A. Parra EE235 4/9/07

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  1. “Detection , Stimulation, and Inhibition of Neuronal Signals with High Density Nanowire Transistor Arrays”ByFernando PatolskyScience: August 2006 Erika A. Parra EE235 4/9/07

  2. Outline • Neuron Terminology • NW-FET & Neurons • Device Fabrication • Results • Signal Propagation • Signal Blocking • Multi-Neurite Structures • Conclusions

  3. Neuron Soma – 3 to 18 um Dendrites – cellular extensions, <1um thick Axon – cable-like projection, can be >1m, also <1um thick Axon terminal IC = intracellular

  4. NW-FETs & Neurons 1. Resting State ~ -70mV Cell Action Potential Na++ K+ 2. Depolarization Na+ + ++ • Potential outside of cell (by NW) becomes more negative (mirror image) • Accumulation of carriers at NW • P-type NW conductance enhanced 3. Repolarization ++ +

  5. Fabrication SiNW (20um) growth via CVD with Au cluster Diborane (B2H6) CVD for doping (p-type) Alignment through flow-directed technique Patterned and deposited contacts for source and drain (Ni). Passivated contacts (Si3N4) to survive cell culture conditions Patterned 50um squares for cell body and 3um wide lines for axion and dendrite grown. Deposited polylysine for adhesion of and directed growth Cell culturing NW-Neuron Array NW Element Optical Yield - 90%

  6. Stimuli Propagation Soma stimulation Simultaneous axon and dendrite peak spreading measurement- new Superimposed signals: • Peak reduction & temporal spreading in dendrite • Measured latency matches previously reported values

  7. Axon-End Signal Blocking NW3 Stimulated • Back propagation signal to soma unaffected by increasing potential • Axon end signal blocking at 0.9V • Suggests action is localized • Propagation speed comparable in both directions through axon Peak amplitude decrease at 0.4V

  8. Multi-Neurite Structures Intracellular NW-Axon axon Soma Biphasic stimuli 500us train width Spike propagation w/o IC electrode 15ms 0.5nA NW4 not connected

  9. Conclusion Signal mapping tool with high spatial and temporal resolution (150 devices with 400nm interspacing) Inhibits or stops signal propagation while mapping signal flow to dendrites and axons Reproducibility of NW-cell devices for flexible real-time cellular assays for drug discovery and testing – 43 out of 50 working devices over 500um axon Possible interface for implanted devices

  10. Current Methods • Micropipette electrodes • Intracellular and extracellular • Resolution of 100nm per pipette and 10um between pipettes • Difficult to multiplex • FET arrays • 10um and larger on edge and 10um between electrodes • Size limits neuron analysis – cannot look at individual axons or dendrites

  11. Neuron Excitation Soma initiated NW-Axon initiated 500ms step of 0.1nA Temporal correlation Applied biphasic potential 1) 0.5V (successful 86%) 2) 0.3V (below threshold) 3) 0.5V after TTX (toxin that blocks action potentials)

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