Flexible microelectrode arrays with integrated insertion devices

Abstract

Flexible microelectrode arrays (FMAs) allow interfacing to delicate living tissues such as neural tissue with a minimum of physical disruption of that tissue during and after insertion. This physical disruption is minimized since the compliant FMAs can deform along with the tissue. However, a problem with these arrays is the insertion and subsequent precise positioning of the arrays in the tissue. Previous FMAs required hand assembly of the flexible array with another rigid structure. This may not be feasible if the dimensions of the flexible array are too small. In this work, FMAs with integrated rigid insertion devices were designed, fabricated, and assessed. Thin-film technology and electrodeposition were used to create flexible arrays with attached rigid insertion devices in a single sequence of fabrication steps. These arrays can be designed in two different configurations. The first type allows for flexible electrodes to be sewn through a nerve. The second allows for insertion into a surface such as the cerebral cortex or the spinal cord. After insertion, the rigid portion of the FMA is removed from the tissue with the flexible portion remaining behind. These two implantation schemes were tested on tissue models and found to be straightforward and reliable. In addition, comparisons of the potential to cause tissue damage between flexible and rigid arrays of similar dimensions were made under three different conditions of mechanical perturbation. In all cases, FMAs caused no damage to the tissue model above that caused by the original electrode insertion track while rigid arrays caused significant tearing. Finally, FMAs were shown to successfully stimulate neural tissue in an experimental setting.