Flexible Hydrophilic Carbon Nanotube Fibers As Microelectrodes for Neuroscience

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Implantable micro electrodes are generally employed to record and stimulate electrical activity of neurons in the nervous system. Most of the electrodes available today are made of metals and silicon that lack required flexibility resulting on a mechanical mismatch between soft tissues and rigid metals which induces faster biofouling and inconsistent performance for long-term applications. Biofouling triggered by inflammatory responses dramatically affect the performance of neural electrodes, resulting in decreased signal sensitivity and consistency over time. Thus, long-term clinical applications require electrically conducting flexible electrode materials with reduced dimensions and antibiofouling properties. These characteristics reduce the degree of inflammatory reactions and increase lifetime of neural electrodes. Carbon nanotubes (CNTs) are well known for their flexibility, electrical conductivity and chemical inertness. This talk will report the use of CNT fibers for neural stimulation and recording, and subsequent covalent functionalization of CNT fibers and films surfaces with hydrophilic, antibiofouling phosphorylcholine (PC) molecules. The electrochemical and spectroscopic characteristics, impedance properties, hydrophilicity, and in vitro antifouling nature of the functionalized CNT surfaces will be presented. The hydrophilicity of the functionalized CNT films was demonstrated by a decrease in the static contact angle from 134.4° ± 3.9° before to 15.7° ± 1.5° after one, and fully wetting after three functionalization cycles respectively. In addition, the extent of protein absorption on the functionalized CNT films were significantly lower than that on the non-functionalized CNT film. Surprisingly, the faradic charge-transfer properties and impedance of the CNT assemblies were preserved after functionalization with PC molecules. These functionalized CNT assemblies are promising for the development of low-impedance neural electrodes with higher hydrophilicity and protein-fouling resistance to inhibit inflammatory responses.