Fluidic Microdrives for Minimally Invasive Implantation and Actuation of Flexible Neural Electrodes Abstract Flexible microelectrodes that match the mechanical properties of the brain promise to increase the quality and longevity of neural recordings by reducing chronic inflammatory reactions; however, these microelectrodes are traditionally difficult to implant without causing acute damage. Because these flexible electrodes are typically more flexible than a human hair, stiffening agents are presently used to temporarily increase the overall size and rigidity of the electrode during implantation. The resulting increase in the electrode footprint damages the tissue, leading to cell loss and glial activation that persists even after the stiffening agents are removed or dissolve. Furthermore, once the electrodes are inserted, they remain fixed in place and cannot be repositioned to record from different brain regions. To overcome the limitations of current flexible electrode implantation methods we propose ?fluidic microdrives?: specially designed microfluidic devices that can insert and microactuate bare flexible electrodes with no need for stiffening agents, thus reducing acute damage during electrode implantation. In this project we will demonstrate that fluidic microdrives can implant and actuate state-of-the art flexible multichannel electrodes in vivo. These experiments will represent the first studies of flexible electrode performance following a minimally invasive implantation. As part of this project we will assess the quality and longevity of neural recordings following fluidic implantation compared to conventional implantation using removable stiffeners. Overall, fluidic microdrive technology proposed here will provide a versatile method to reduce tissue damage associated with implantation and actuation of flexible neural electrodes that could be adapted to support a variety of electrode materials and geometries.
Implantable microelectrodes are a valuable tool for applications that require decoding the activity of individual neurons at high spatial and temporal resolution, such as brain-machine interfaces and neuroprosthetic devices. Early work using large and stiff electrodes showed that these devices trigger a foreign body reaction in the host tissue that can reduce the quality and longevity of the recordings. Smaller, flexible electrodes reduce the foreign body response; yet there are currently no technologies to insert and reposition these electrodes without stiffeners that increase the size of the electrode and produce acute damage. The fluidic microdrive technology proposed here will enable implantation and actuation of bare state-of-the-art flexible electrodes without using stiffeners or shuttles and thereby dramatically reduce acute neural damage during electrode implantation.
