[Faculty] Fwd: [CSRC-SDSU COLLOQUIUM]: Highly Stable Glassy Carbon Interfaces for Long-Term Neural Stimulation and Low-Noise Recording of Brain Activity

[Jose Castillo]

*DATE: * Friday, March 10th, 2017

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

*TIME: * 3:30 PM

*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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