Design, engineering, and evaluation of a novel microgrid electrode array to monitor the electrical activity on the surface of the cerebral cortex

The purpose of the study was to design and engineer a novel microdevice, a microgrid electrode array, that can further biomedical engineering research in the areas of neuroscience and neurology. Polymer microfabrication techniques were developed to create the microdevice, which is capable of measuring electrical activity on the surface of the cerebral cortex. Importantly, the activity obtained is at a greater level of spatial resolution than can be found in the current research for surface electrode grids. In fact, the device has been designed such that the activity of individual cortical columns, the functioning units of brain cortex, can be obtained. Although penetrating microelectrodes are capable of detecting this level of detail, their invasiveness limits their use to human cortical tissue destined for surgical resection or strictly to animal studies. The development of a less-invasive non-penetrating microgrid electrode array suitable for human use provides medical scientists with a unique and powerful tool for detailed brain mapping, gaining a better understanding of human cortical columns function, as well as for exploring diseases and therapy options associated with the brain cortex.; Internal Review Board (IRB) approvals for the use of the device with a pig animal model and with human patients were obtained from the respective committees at The Ohio State University. The polymer microfabrication process protocol was developed at the Ohio MicroMD facility. The fabrication protocol includes several standard photolithography steps and many novel chemical and encapsulation methods. Characterization of the fabrication protocol steps and testing of the electrical connection integrity was performed using Scanning Electron Microscopy (SEM), optical microscopy, profilometery, and a microprobe station. Cyto-compatibility testing of the microgrid electrode with mammalian and human cortical cells consisted of qualitative analysis, using optical microscopy and standard cell-staining techniques, and quantitative analysis, using Laser Scanning Cytometry (LSC). The experimental surface (microgrid electrode surface) was compared with a control surface that is known to be cyto-compatible. Evaluation with an anesthetized pig animal model consisted of collecting Visual Evoked Potentials (VEPs) by interfacing the microgrid electrode device with a BiologicRTM data acquisition system.; Results from the different polymer fabrication processes revealed that the desired geometries of the features on the device were maintained. (Abstract shortened by UMI.)...