A novel pattern transfer technique for mounting glassy carbon microelectrodes on polymeric flexible substrates. (12th January 2016)

• Record Type: Journal Article
• Authors: Vomero, Maria; van Niekerk, Pieter; Nguyen, Vivian; Gong, Nick; Hirabayashi, Mieko; Cinopri, Alessio; Logan, Kyle; Moghadasi, Ali; Varma, Priya; Kassegne, Sam
• Is Part Of: Journal of micromechanics and microengineering. Volume 26:Number 2(2016:Feb.)
• Publication Date: 2016-01-12
• Subjects: MEMS -- C-MEMS -- polyimide -- neural probe -- glassy carbon -- SU-8 -- pyrolysis; Microelectromechanical systems -- Periodicals; Micromechanics -- Periodicals; 621.38105
• DOI: 10.1088/0960-1317/26/2/025018
• Languages: English
• ISSNs: 0960-1317

Abstract

Abstract: We present a novel technology for transferring glassy carbon microstructures, originally fabricated on a silicon wafer through a high-temperature process, to a polymeric flexible substrate such as polyimide. This new transfer technique addresses a major barrier in Carbon-MEMS technology whose widespread use so has been hampered by the high-temperature pyrolysis process (⩾900 °C), which limits selection of substrates. In the new approach presented, patterning and pyrolysis of polymer precursor on silicon substrate is carried out first, followed by coating with a polymer layer that forms a hydrogen bond with glassy carbon and then releasing the ensuing glassy carbon structure; hence, transferring it to a flexible substrate. This enables the fabrication of a unique set of glassy carbon microstructures critical in applications that demand substrates that conform to the shape of the stimulated/actuated or sensed surface. Our findings based on Fourier transform infared spectroscopy on the complete electrode set demonstrate—for the first time—that carbonyl groups on polyimide substrate form a strong hydrogen bond with hydroxyl groups on glassy carbon resulting in carboxylic acid dimers (peaks at 2660 and 2585 cm −1 ). This strong bond is further confirmed by a tensile test that demonstrated an almost perfect bond between these materials that behave as an ideal composite material. Further, mechanical characterization shows that ultimate strain for such a structure is as high as 15% with yield stress of ~20 MPa. We propose that this novel technology not only offers a compelling case for the widespread use of carbon-MEMS, but also helps move the field in new and exciting directions.