A Parylene Cuff Electrode for Peripheral Nerve Recording and Stimulation
Angelica Cobo1, Kee Scholten1, James Yoo1, Christopher Larson1, Trevor Hudson1, Victor Pikov2,Ellis Meng1
1 Department of Biomedical Engineering, University of Southern California, US
2 GlaxoSmithKline, UK
Topic Area: Peripheral Nerve Interfaces
Introduction: The creation of a versatile, noninvasive brain-computer interface is key to thedevelopment of new medical technologies including advanced prostheses, however achieving astable electrophysiological connection to peripheral nerves is challenged by the presence of theepineurium sheath which limits access to individual nerve fibers. Intraneural devices, which
physically penetrate this sheath, achieve strong signal fidelity but are overly invasive. To overcome
these hurdles, we developed a non-invasive Lyse-and-Attract Cuff Electrode (LACE) withintegrated direct-to-nerve drug delivery system as a means to chemically disrupt the epineurium
and then promote axonal sprouting towards electrodes within the microchannels.
Methods: The Parylene C cuff incorporates 4 microfluidic channels (250 μm W × 20 μm H), eachcontaining a pair of platinum electrodes (300 μm W × 1500 μm L). The cuff wraps around a nervewith the microfluidic outlets in contact around the circumference of the epineurium, and is held in
position by an adjustable locking mechanism. During benchtop testing devices were wrapped andunwrapped around simulated agarose nerve phantoms to evaluate holding strength (n > 10).
Microfluidic channels were evaluated by infusing dye with a syringe pump at variable flow rates
while imaging dye progression. Baseline electrochemical measurements were obtained throughcyclic voltammetry in a 0.05M H2SO4 and electrochemical impedance spectroscopy in 1X PBS.
Results: The locking mechanism was simple to implement and robust. No leakage was observed
up to a flow rate of 2000 μL/min, with uniform flow through all fluidic outlet ports in the flat
configuration (n = 4). In the curled configuration, flow was achieved in 3 out of 4 channels which
is sufficient for the in vivo application. Localized drug delivery on a nerve phantom wasdemonstrated. A safe flow rate of 900 nL/min was achieved by the cuff when wrapped around anerve phantom. Cuff electrodes yielded an electrical impedance of 1.8 kΩ, a phase of -56.4º at 1kHz, and a charge storage capacity of 1.06 mC/cm2 (n = 6), demonstrating suitable electrodeproperties for peripheral nerve recordings and stimulation.
Conclusion: We developed a peripheral nerve interface that combines electrodes and microfluidic
channels in an adjustable cuff sized to interface with rat sciatic nerve. The LACE device uses arobust and simple locking mechanism that is adjustable for close contact with nerves of varying
diameters. We demonstrated fully functional cuffs having low electrode impedances, microfluidic
infusion at < µL/min flow rates, and localized drug delivery.

Figure 1. (a) Schematic of LACE for targeting individual fascicles within a nerve. Insert shows the cross-sectional view. (b)Fabricated LACE in which microfluidic channels are highlighted by the presence of photoresist.

Acknowledgements:
This work was supported under DARPA cooperative agreement HR0011-15-2-0006, Viterbi School ofEngineering Ph. D. Merit Fellowship (AC), and USC Provost Fellowships (JY and TH). The authors wouldlike to thank Dr. Donghai Zhu and the members of the USC Biomedical Microsystems Laboratory for theirassistance with this project.
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