Carbon MEMS
Carbon MEMS
Research Background
Carbon has been used for thousands of years by almost all human cultures, although only recently we have started appreciating its scientific and technological applications. The highly heterogeneous properties of its multiple allotropic forms (amorphous carbon, diamond, graphite, carbon nanotubes, fullerenes, etc.) make carbon an excellent engineering material for a whole new range of applications.
Carbon-MEMS refers to a microfabrication technique in which photopatterned resists, heat treated (pyrolyzed) at different temperatures in different ambient gases, are used as a carbonaceous structural and functional material for micro electromechanical systems (MEMS). This new material permits an entire new variety of novel MEMS applications that employ structures having a wide variety of shapes, resistivities and mechanical properties. Moreover, carbon surfaces form better electrochemical electrodes and are easier to derivatize with organic molecules than more traditional MEMS materials such as silicon. [4]
One of the first applications of Carbon-MEMS has been in energy storage systems. Highly ordered graphite as well as hard and soft carbons are used extensively as the negative electrodes for commercial Li-ion batteries. For small microbatteries, with applications in miniature portable devices, the achievable power and energy densities do not scale down favorably because packaging and internal battery hardware determine the overall size and mass of the completed battery to a large extent. One possible approach is to develop 3D battery architectures based on specially designed arrays composed of high aspect ratio 3D electrode elements. Our work on C-MEMS suggests that they might provide an interesting material and a microfabrication solution to the battery miniaturization problem. Out of this effort, a spin-off company, Carbon Micro Battery, has been created.
Another domain that holds considerable promise is the biological applications of C-MEMS. Pyrolytic carbon has been long used as a material for heart valves implants due to its blood clotting preventing properties. One of the ongoing research projects consists in characterizing the biocompatibility properties of photoresist-derived pyrolytic carbon. At the same time , due to the excellent electrochemical properties of carbon, we are proposing to build a multiplexed potentiostats based on arrays of carbon microelectrodes. This new tool will find applications that extend from basic electrochemistry research and dielectrophoretic devices to biological cell stimulation, DNA detection, and drug delivery systems.
Related Collaborators & Start-Ups
Relevant Publications
[1] C. Wang, G. Jia, L. Taherabadi and M. Madou, A Novel Method for the Fabrication of High-Aspect Ratio C-MEMS Structures, J. of Microelectromech. Systems, vol. 14(2), pp. 348-358, 2005.
[2] Ranganathan, S., McCreery, R., Majji, S.M., Madou, M.J., Photoresist-Derived Carbon for Microelectromechanical Systems and Electrochemical Applications, Journal of the Electrochemical Society, Vol. 147(1), pp. 277-282, 2000.
[3] Kim, J., Song, X., Kinoshita, K., Madou, M.J., White, R., Electrochemical Studies of Carbon Films from Pyrolyzed Photoresist, Journal of the Electrochemical Society, Vol. 145(7), pp. 2314-2319, 1998.
[4] M. Madou et al. “Carbon Micromachining (C-MEMS)”, Electrochem. Soc. Proceed. 97-19, pp. 61-69, 1997.
Projects
C-MEMS Process
