Erika A. Parra EE235 4/9/07

 Neuron Terminology  NW-FET & Neurons  Device Fabrication  Results Signal Propagation Signal Blocking Multi-Neurite Structures  Conclusions

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

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

1.SiNW (20um) growth via CVD with Au cluster 2.Diborane (B 2 H 6 ) CVD for doping (p-type) 3.Alignment through flow- directed technique 4.Patterned and deposited contacts for source and drain (Ni). Passivated contacts (Si 3 N 4 ) to survive cell culture conditions 5.Patterned 50um squares for cell body and 3um wide lines for axion and dendrite grown. Deposited polylysine for adhesion of and directed growth 6.Cell culturing Yield - 90% OpticalNW ElementNW-Neuron Array

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

NW3 Stimulated Peak amplitude decrease at 0.4V 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

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

 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

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

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