Hydrophilic modification of neural microelectrode arrays based on multi-walled carbonnanotubes

Abstract

To decrease the impedance of microelectrode arrays, for neuroscience applications we havefabricated and tested MEA based on multi-walled carbon nanotubes. With decreasingphysical size of a microelectrode, its impedance increases and charge-transfer capabilitydecreases. To decrease the impedance, the effective surface area of the electrode mustgenerally be increased. We explored the effect of plasma treatment on the surfacewettability of MWCNT. With a steam–plasma treatment the surface of MWCNT becomesconverted from superhydrophobic to superhydrophilic; this hydrophilic property isattributed to –OH bonding on the surface of MWCNT. We reported the synthesis at400 °C of MWCNT on nickel–titanium multilayered metal catalysts by thermal chemical vapordeposition. Applying plasma with a power less than 25 W for 10 s improved theelectrochemical and biological properties, and circumvented the limitation of the surfacereverting to a hydrophobic condition; a hydrophilic state is maintained for at least onemonth. The MEA was used to record neural signals of a lateral giant cell from anAmerican crayfish. The response amplitude of the action potential was about275 µV with 1 ms period; the recorded data had a ratio of signal to noise up to 40.12 dB. Theimproved performance of the electrode makes feasible the separation of neural signals andthe recognition of their distinct shapes. With further development the rapid treatment willbe useful for long-term recording applications.