Cortical electrodes offer an intimate interface to the complex activity of the brain. They are an enabling technology for advanced brain therapies that will significantly enhance the human condition, as well as, fundamental tools for investigating the operation of the brain. One of the limiting factors of current technology is a mechanical mismatch between the electrode and the cortical tissue. While a stiff electrode is advantageous during implantation and positioning, a chronically stiff electrode causes micro-motion, micro-damage, and chronic astrocytic response in the brain tissue. An ideal electrode would have a high modulus during insertion and a low modulus thereafter. Inspired by the soft connective tissues of echinoderms, we have embarked on the exploration of a highly innovative and novel general class of polymer nanocomposites, which are targeted to dynamically change their mechanical properties in response to a stimulus, such as temperature or pH change, electrical or optical field, or concentration of specific ions. We propose to exploit chemical stimuli (ion concentrations or pH) for the mechanical switching of polymers that form the basis of adaptive cortical electrodes. Initial feasibility of the mechanically dynamic properties of the composites have already been demonstrated. In this proposal we will further study their properties and develop them for use in biomedical applications.
The first aim i s to optimize the composition for optimal performance in the cortex environment. The optimal material will be stiff in an ambient environment and dynamically change in response to the chemical environment of the cortex to match the cortical tissue mechanics when implanted. We will characterize the mechanical properties and dynamics, as well as, the basic techniques processing the material into devices designed for biological applications.
The second aim i s to understand the chronic astrocytic and tissue response to the polymer. The overall goal of this project is create and understand a stimulus-responsive, mechanically dynamic nanocomposite available for biomedical and neuroprosthetic applications. The first application studied in this proposal will be as a substrate for cortical electrodes. ? ?
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