The objective of this project is to evaluate graphenated carbon nanotubes (gCNTs) as lower impedance, smaller electrodes for neurostimulation, using deep brain stimulation (DBS) as a test case, with the long-term goal of developing a new type of neural electrode with lower impedance and smaller size. Lower impedance of the electrode-tissue interface results in lower power consumption, as a smaller voltage is required to achieve the same charge injection. Lower power consumption extends battery life and decreases the size of the batteries and thus of the implanted device. The minimum size of stimulating electrodes is limited by the minimum charge injection required for effective stimulation. As well, the size of the electrode is an important factor in the insertion damage created by electrode insertion and the specificity of the volume that can be stimulated. Lower impendence, smaller electrodes will lead to less damaging electrodes and a combination of smaller and longer lasting batteries. We will compare the performance of gCNT electrodes to standard platinum electrodes using quantitative in vitro and in vivo measurements. We expect to increase the reversible charge injection capacity by 20x and reduce the impedance by 65% versus the same-sized Pt electrode. The specific aims of this project are: (1) Quantify the effect of gCNT morphology on charge injection, interfacial impedance, and adhesion and identify processing conditions that improve these properties. (2) Deposit platinum nanoparticles via atomic layer deposition (ALD) on gCNTs to further increase the charge injection capacity and decrease impedance. These Pt-gCNTs will be deposited in a checkerboard pattern (balance Pt electrodes) on a multielectrode array (MEA), allowing performance to be compared within animal (3). Test the MEAs in vivo in hemiparkinsonian 6-OHDa lesioned rats, implanting electrodes into the subthalamic nucleus and delivering chronic daily symptom-relieving DBS in order to assess Pt-gCNT vs Pt electrode performance. In the applicant’s opinion, proposed research is innovative because it introduces a new material (gCNTs) and a new process (ALD) that will improve the performance of neural electrodes. gCNTs are expected to have significantly better performance than standard Pt electrodes. ALD has the capability to deposit nanoparticles in a unique way that maximizes the amount of gCNTs surface area that is coated as well as the electrochemical surface area of the platinum. Nanostructured platinum will be used to further enhance gCNTs’ neural electrode performance. The outcome of this project will be a comprehensive assessment of Pt-gCNTs as highly efficient neural stimulation electrodes. If realized, it will lead to neural stimulation electrodes that are smaller, limiting insertion damage, and consume less power, thereby reducing the size and increasing the lifetime of batteries and may expand the frontier of possible electrode systems.

The proposed research on graphenated carbon nanotube-based electrodes is relevant to public health because it will allow the creation of neural stimulation electrodes that will alleviate symptoms of Parkinson’s disease, Essential tremor, and potentially other neural stimulation applications. These electrodes will be smaller, causing less damage to the brain, and have lower power consumption, so batteries will last longer and need to be replaced less frequently, thus it is relevant to that part of the NIH’s mission related to reducing illness and disability.