Erika A. ParraEE2354/9/07

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 (B2H6) CVD for doping (p-type)

3. Alignment through flow-directed technique

4. Patterned and deposited contacts for source and drain (Ni). Passivated contacts (Si3N4) 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 stimulationSimultaneous 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-AxonIntracellular

15ms 0.5nANW4 not connected

Biphasic stimuli500us 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

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

500ms step of 0.1nATemporal correlation

Soma initiated NW-Axon initiated

Applied biphasic potential1) 0.5V (successful 86%)2) 0.3V (below threshold) 3) 0.5V after TTX (toxin that blocks action potentials)