Growth of nano-wrinkles on photoresist-derived carbon microelectrode array

Abstract

A novel fabrication method for integrating nano-wrinkles to carbon microelectromechanical systems (C-MEMS) posts on a silicon substrate is proposed in this paper. In the fabrication of carbon microelectrode array, SU-8, a negative photoresist is patterned by photolithography and subsequently pyrolysed at high temperatures in an oxygen-free environment. In this process, the SU-8 posts are slowly converted to the desired carbon posts with properties resembling those of glassy carbon, and the carbon posts have shrinkage in both vertical and radial directions. As we deposit a thin layer (nanoscale order) of carbon before pyrolysis, nano-wrinkle patterns can be generated with the shrinking of the photoresist due to a large difference in the elastic moduli as well as high compressive stress. The nano-wrinkles generated in carbon films can greatly enlarge specific surface area, which significantly enhances the electrochemical performance compared to the blank posts. Since the carbon nano-wrinkles have the same nature as the carbon posts, the stability and biological compatibility of nano-wrinkles integrated microelectrodes are greatly enhanced.