A PDMS-based Elastic Multi-Electrode Array for Spinal Cord Surface Stimulation and Its Electrode Modification to Enhance Performance

摘要

For our ongoing research involving electrical stimulation of rat spinal cord axonal tracts, it is desirable to use a microelectrode array which highly conforms to the surface of the spinal cord. The elastic polymer, polymethylsiloxane (PDMS, known commercially as Sylgard), possesses properties which make it suitable to meet this demand by serving as the electrode substrate. In addition to elasticity, cured PDMS is also gas permeable and biocompatible, and the surface multi-electrode array (MEA) fabricated on such a substrate would cause minimal damage to the cord in that the electrodes do not penetrate spinal tissue. Using standard microfabrication technology, we have previously implemented such an elastic MEA on the PDMS substrate(Fig. 1a). Our fabrication process involves patterning gold traces onto a PDMS substrate cured on a glass slide, covering the traces with another thinner PDMS layer for insulation, and then exposing the sites of electrodes and contact pads. The advantages of fabrication of this type of MEA include achievement of high electrode spatial density, high geometrical precision, and ability to be fabricated easily in batches with little geometrical and electrical difference between each other. These advantages in turn enable high spatiotemporal stimulation selectivity and parallel stimulation capabilities, as well as reliable data reproducibility.