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MAE 589M Final Project A novel neuromorphic micro robotic neural probe Riley Zeller-Townson Haibo Zhao Date: 12/09/2008 Project Overview • • • • Preformed literature Review Found gap in current technology Proposed design Proposed fabrication method for design Background • Many applications for reading neuron voltages (neuroprosthetics, stimulation) • Neurons pass electrochemical signals to each other • Neurons connect using long, skinny extensions (axons and dendrites) History Lesson • Need to be able to monitor minute electric, chemical signals • First experiments on squid giant axon (Cole, Hodgkin) • First real microelectrodes: hollow glass tubes • Teflon coated microwires • Michigan Probes, Utah Arrays, SOI Current Work • Biocompatibility – Surface coating – Flexibility – Probe geometry • Microfluidics – Deliver and sample • Signal quality Problem Definition • No design that physically resembles a neuron, though geometry a component of biocompatibility • Electrodes should be placed like synapses on neuron • Should be able to release chemical signals (contain microfluidic channels) • Electrodes/ microfluidics on arms (dendrites) • Arms can 'grow' into surrounding tissue • Arms stored between concentric cyllinders How it works • Inner shaft acts as water main for all microfluidic channels, connects to each arm • Drive actuators feed arms in and out • Arms bend and rotate around inner shaft Shuffle Drive Actuator Actuator Dynamics • EI (d4v(x))/(dx4) – S(d2v(x)/dx2) = 0 • v = Fel3 * (1 – cosh(k) – cosh(Kz) + zKsinh(K) + cosh(K(z-1)))/(EI 2 K3sinh(K)) • d = 2 ∫01 √(1+(dv/dx)2)dx -2l • y = Fel3 /24EI (3 * 1/2K-tanh(1/2K)/(1/2K)3 ) Actuator Dynamics, cont • Fe = ½ CV2 /d • Voltage = Q/A(d1/ε1 + d2/ε2 + d3/ε3) • Capacitance = Q/V = A/(d1/ε1 + d2/ε2 + d3/ε3) • Capacitance = ε0A/d2 • d = (1/2 to 3/5) * ε0A *½ V2 /d2 *l3/(24EI) (3 *( 1/2K-tanh(1/2K))/(1/2K)3 ) Fabrication Process Al deposition Mask #1 Mask #2 Fabrication Process Continued Parylene deposition Mask #3 Mask #5 Mask #6 Mask #4 Fabrication Process Continued Photoresist deposition Parylene deposition Mask #7 Fabrication Process Continued Platinum Patterning Thermal bonding Electrode Isolation Lifting off glass wafer Parylene deposition on glass wafer Fabrication Process Continued Mask #8 Al etchmask patterning Parylene etching Fabrication Process Continued Al etching Photoresist deposition Fabrication Process Continued Mask #9 Al etchmask patterning Photoresist etching Fabrication Process Continued Photoresist Etching and Parylene Etching Parylene deposition Al etchmask patterning Release from silicon mold by aluminum dissolution Fabrication Process Finished Photoresist dissolution Conclusions • Completed design that should incorporate several biocompatibility techniques • Created fabrication process for sophisticated probe design • More modeling necessary • Some more specific dimensions Thank you for your time Any questions?