Surface Modification of Neural Electrode with Electrodeposited - PowerPoint PPT Presentation

2019 US-Korea Nanoforum Surface Modification of Neural Electrode with Electrodeposited Nanoparticles for Stimulation Performance Enhancement Synapse Devices Creative Research Section

Application Potentials  Applications for neurological disorders Synapse Devices Creative Research Section

Multi-electrode Array (MEA)  Definition MEAs or microelectrode arrays are devices that contain multiple micro plates – Extracellular recording & stimulation – – 1 st MEA by Thomas Jr. (1972) & commercialized by Multi-Channel Systems  (1996)  Application potential Disease model Drug screening Cell-based sensors Network modelling Learning Synapse Devices Creative Research Section

Specifications Requirements for neural-computer bi-directional interface  Decoding Recording • High SNR: » 5 • Low noise • Long-term viability • Temporal resolution • Electrode size: <30 μm – Single unit recording • High # of channel: ~256 CH • Intimate contact • Spike sorting Stimulation Charge injection capacitance: » • Charge injection limit: » 1 mC/cm 2 • Charge injection efficiency: ~1 • Damage threshold: 1 mC/cm 2 • Long-term durability • Field focality • Encoding Synapse Devices Creative Research Section

Extracellular Recording & Stimulation  Recording issue Impedance control for reduction of interfacial noise –  ) Δ f N e.e = √4 k T Re ( Z e   1 / A s Z e 2  Stimulation Charge storage capacitance – Charge injection limit – • Electrochemical window: -0.64 ~ 0.75 V (vs. SCE)* • Safety limit: ~ 1 mC cm -2 ** Material dependence –  Common requirement 𝑟 𝑑 = 𝐷 𝑒𝑚 ∆𝑊 Increase in surface area –  Long-term reliability issues Synapse Devices Creative Research Section

Nanomaterials for surface modification Pt black TiN IrOx PEDOT 1980 Pine 1998 Egert 2002 Weiland 2004 Xiao Au NW CNT NP Pt Layered Au NPs 2007 Yoon 2009 Shein 2010 Park 2012 Zhang NPG Au nanoflake CP CNT + Au NP 2010 Seker 2010 Kim 2010 Abidian 2014 Zhang from Chapman & Seker (2017) PEDOT + CNT Ir-NiO 2014 Castagnola 2014 Stilling Synapse Devices Creative Research Section

Primary neuronal cell culture  SD rat Incubator Synapse Devices Creative Research Section

Electrode Materials for Neural Interface  Five criteria* Tissue response – Allergic response – Electrode-tissue impedance – Charge injection capability – Radiographic visibility –  Metals List of biocompatible metals – • Au, Pt, Pt-Ir, stainless steel, Pd, W, Pt-Rh, Cr-Mo, Au-Ni-Cr, Au-W, Ti, IrOx, List of improper metals – • Fe, Cu, Ag, Co, Zn, Mg, Mn, Al, Bi, Cd, Ni Hierarchy of allergenic metals – • Be > Hg > Cu > Au > Ag Best candidates as implants –  Nanostructures Nanostructures • Au, Pt, W, Rh, Pd, Ti Nanoparticles Choice for stimulating electrodes – – Nanorods – • Pt, Pt-Ir, Au, W, Rh Nanowires –  Non-metals Nanoflakes – Organic materials – Nanoporous structures – • CNT, conducting polymers Inorganic materials – • ITO, IrOx, Synapse Devices Creative Research Section

Fabrication of MEA Bi-layer lift-off resist technique  Lift-off resist + Negative photoresist + Sputter deposition of SiO 2 – Au ITO Negative PR Lift-off resist Excellent uniformity in impedance Y.H. Kim et al., Fabrication of multi-electrode array platforms for neuronal interfacing with bi-layer lift-off resist sputter deposition, J. Micromech. Microeng. 23, 097001 (2013) Y.H. Kim et al., Optimization of bi-layer structure formation and SiO 2 sputter-deposition process for fabrication of gold multi-electrode array, RSC ф~30 μm Advances 5, 6675 (2015) Synapse Devices Creative Research Section

Electrodeposition of metallic nanoparticles Typical 3-electrode configuration  MEA electrode (working), Pt foil (counter), Ag  AgCl (reference) – Electrochemical characterization  Electrodeposition – Electrochemical impedance spectroscopy (EIS) – C-V – voltage transient – Synapse Devices Creative Research Section

 List of electrodeposited metallic nanostructures Au NPs Pt NPs Au-Pt NPs Pt black NPG Synapse Devices Creative Research Section

Au NP Au-Pt NP Pt NP Au 50 50 50 40 30 30 30 Amplitude(  V) Amplitude(  V) Amplitude(  V) 20 10 10 10 0 -10 -10 -10 -20 -30 -30 -30 -40 -50 -50 -50 0 20 40 60 0 20 40 0 10 20 30 40 50 60 0 10 20 30 40 50 60 Time(s) Time(s) Time(s) 200 * 200 * 100 100 Amplitude (  V) Amplitude (  V ) Bare gold 0 0 8 10 Au NPs Au-Pt Nps -100 -100 7 10 -200 -200 lZl (Ohm) 30 40 50 60 0 10 20 30 * 200 200 6 10 * 100 100 Amplitude (  V) Amplitude (  V ) 5 10 0 0 4 10 -100 -100 -1 0 1 2 3 4 5 10 10 10 10 10 10 10 -200 -200 Frequency (Hz) 44.180 44.185 44.190 44.195 3.000 3.005 3.010 3.015 Time (sec) Synapse Devices Creative Research Section Time (sec)

Modification with nanoporous Au (NPG) Au MEA Electro-co-deposition Chemical leaching Electrodeposition of of Ag:Au on Au of Ag in conc. IrOx on NPG Nitric acid @ 70 ℃ Y.H. Kim et al., In vitro extracellular recording and stimulation performance of nanoporous gold-modified multi- electrode arrays, J. Neural Eng. 12, 066029 (2015) Y.H. Kim et al., Iridium oxide-electrodeposited nanoporous gold multielectrode array with enhanced stimulus efficacy, Nano Lett. 12, 066029 (2016) NPG Synapse Devices Creative Research Section

9 10 bare Au electrode Au NP-modified electrode nanoporous Au-modified electrode 8 10 7 10 Au NP 0.020 lZl (  ) 100-cycled IrOx/Au Au 50-cycled IrOx/NPG 6 10 0.015 70-cycled IrOx/NPG Current (A/cm 2 ) 100-cycled IrOx/NPG 0.010 5 10 NPG NPG 0.005 4 10 0.000 -1 0 1 2 3 4 5 10 10 10 10 10 10 10 Frequency (Hz) -0.005 -0.010 NPG IrOx/Au -0.015 -0.020 Au -0.9 -0.6 -0.3 0.0 0.3 0.6 0.9 V vs. Ag/AgCl, sat'd KCl IrOx/NPG Synapse Devices Creative Research Section

 Cont’d Cathodic charge storage capacitance (cCSC) vs. charge injection limit – Derived from voltage transient measurement – Water window, -0.6 V – cCSC Charge injection Efficiency Material (mC/cm 2 ) limit (mC/cm 2 ) ( CIL/cCSC) 0.1-0.35, 0.05- Pt 9 0.15 Time duration 100  s Au 0.27 50  A V vs. Ag/AgCl, Sat'd KCl 6 100  A Pt black 16 300  A TiN 0.87 500  A 3 1000  A PEDOT 2.3  0.6 0 Roughed Pt >8.9 1.0 CNT 1.6 1-1.6 -3 23.54 , 16, EIROF 1.27 0.054 25 -6 36.15, 54, SIROF 2-3, 4.6  1 0.13 31.5  6.6 -9 0.0 0.1 0.2 0.3 0.4 0.5 NPG 1.0 0.98 ~1 Time (ms) IrOx / NPG 8.8 2.3 0.26 The charge injection limit is defined as the maximum quantity of charge that an electrode can inject before – reaching the water electrolysis potential Synapse Devices Creative Research Section

 Stimulation performance NPG IrOx/NPG Synapse Devices Creative Research Section

 Durability test 1200 fEPSPs peak amplitude (µV) 1st DAY 1000 25th DAY 800 600 400 200 0 0 0.1 0.5 1 2 3 4 5 6 7 Stimulation intensity (V) • 8 hours a day, 25 th day of use Excellent mechanical durability • • Excellent anti-corrosion ability ? Some MEA manufacturers recommend • ‘Do not apply sonication’ Synapse Devices Creative Research Section

Flexibility of LOR passivation technique  Synapse Devices Creative Research Section

NEXT  Mushroom-type MEA for slice tissue interfacing  LOR passivation + electro-co-deposition of Ag:Au alloy Synapse Devices Creative Research Section

64 & 128 CH MEA System  FPGA-based 128 CH bi-directional MEA system MEA Analog front-end • 128 channel recording (4.16 MSamples/s) • Real-time online spike sorting (feature learning & extraction capability) • 8 channel arbitrary voltage and current stimulation J. Park et al., A 128 channel FPGA-based Real Time Spike Sorting Bidirectional Closed-loop Neural Interface System, IEEE Transactions on Neural Systems & Rehabilitation Engineering, Vol. 25, 2227-2238 (2017). Synapse Devices Creative Research Section

All metal-oxide-based MEAs E Overhang formation I ITO etching A ITO cleaning F SiO 2 deposition J PR stripping B ITO etching G Lift-off C PR stripping K IrO x electrodeposition D Bi-layer coating H ITO NW growth SiO 2 ITO Lift-off resist Negative PR Positive PR IrO x Synapse Devices Creative Research Section

Fabrication of flexible electrode Fluoropolymer-based flexible electrode  Fluorinated ethylene propylene (FEP): m. p. ; Tg – FEP plasma treatment and thermal pressing beyond the meting temperature – Solely composed of FEP and Au without adhesion metal – Ar plasma FEP FEP FEP FEP Cr & Au patterning Thermal pressing RF plasma pretreatment RF plasma treatment O 2 plasma Al patterning RF plasma etching Impedance control Cr etching Y.H. Kim et al., Fluoropolymer-based flexible neural prosthetic electrodes for reliable neural interfacing, ACS Appl. Mater Interfaces, Vol. 9,43420-43428 (2017). Synapse Devices Creative Research Section

16-CH ECoG electrode array  Excellent chemical stability Longer than an hour in conc. Nitric acid @ 70 ℃ – Synapse Devices Creative Research Section

Co-work Program  Reliability test with primate platform Synapse Devices Creative Research Section

Synapse Devices Creative Research Section