Integration of Microfluidic Channels into Laser-Fabricated Neural Electrode Arrays

Abstract

Neural interfaces are most commonly of electrical/electrochemical nature, employing metal electrodes that allow sensing of neural activity or stimulation of nerve cells by introduction of electrical currents. Some interfaces require additional ports for localized release of chemical agents, such as drugs that alter the behavior of the neural system, or dies that allow labeling of regions in the observed tissue for subsequent histological studies. In this paper we present a fabrication procedure for neural electrode arrays based on laser-ablation of medical grade silicone rubber and platinum foil, to which an additional laser-process is added in order to integrate fluidic channels into the silicone substrate. A variety of channels were produced having cross sectional areas ranging from approx. 40 · 80 µm² to 130 · 170 µm². In order to characterize the main fluidic properties of such channels, the pressure/flow rate ratio was measured and the burst pressure for two different channel geometries was determined.

As a proof of concept, a prototype of a microfluidic nerve electrode was fabricated, having 4 metal electrodes and one fluidic channel that branches to each of the metal electrodes, ending in nozzles located at the rim of each electrode surface. The fluid dynamics were visualized by injecting died solvent into the channel inlet; a simultaneous escape of the fluid on each electrode site was observed.