TITLE:

Highly Stable Glassy Carbon Interfaces for Long-Term Neural Stimulation and Low-Noise recording of Brain Activity Composites

DATE:

Friday, March 10th, 2017

TIME:

3:30PM

LOCATION:

GMCS 314

SPEAKER:

Dr. Sam Kassegne, PhD, MEMS Research Lab, Department of Mechanical Engineering, SDSU.

Abstract:

As research and clinical interest in interfacing microelectrodes with tissues, for applications ranging from sensing and stimulation of neural signals in BCI (brain-computer-interface) for sensorimotor control, to chronic pain management and DBS (deep brain stimulation) increases, electrode materials with superior long-term performance are finding renewed importance. Electrodes that are part of BCI systems require materials that are capable of interfacing with the brain and spinal cord without inducing tissue responses while both recording signals as well as electrically stimulating neural cells. In this talk, we report on a new electrode material fabricated from lithographically patterned glassy carbon (GC) that promises to achieve this by combining superior electrochemical properties for neural recordings and better long-term stability under electrical stimulation than current thin-film metal microelectrodes. We demonstrate that lithographically patterned glassy carbon microelectrodes can withstand at least 5 million pulses at 0.45mC/cm2 charge density with < 7.5% impedance change, have > 70% wider electrochemical window and 70% higher CTC (charge transfer capacity) than platinum (Pt) microelectrodes of similar geometry, which delaminated after 1 million pulses. For direct comparisons, ultra-flexible, micro-electrocorticography (μ-ECoG) arrays with GC electrodes were manufactured using recently introduced pattern transfer techniques, while thin-film platinum arrays were fabricated using conventional microfabrication methods. The electrode arrays biocompatibility was demonstrated through in-vitro cell viability experiments, while acute in-vivo characterization was performed in rats and showed that GC microelectrode arrays recorded somatosensory evoked potentials (SEP) with an almost twice SNR (signal-to-noise ratio) when compared to the Pt ones. Additionally, poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) was selectively electrodeposited on both sets of devices to specifically reduce their impedances for smaller diameters (< 60μm). We observed that PEDOT-PSS adhered significantly better to GC than Pt, presumably due to stronger interaction between GC and carbonaceous PSS-PEDOT chains, and allowed drastic reduction of electrode size while maintaining same amount of delivered current.

HOST:

Dr. Jose Castillo

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