Prof. Yonggang Meng

Department of Mechanical Engineering, Tsinghua University

Microelectromechanical systems (MEMS) are usually fragile to wear problems. In this research, a bulk-fabricated side-wall Si-MEMS tribotester with the feature of on-chip buckle loading mechanism was designed and used to study the wear life and the mechanisms of early stage wear of resonant MEMS devices in different gas environments. Two distinguishable wear mechanisms are recognized: (1) in dry N2 or O2/N2 mixture environments, wear exhibited an adhesive feature that the instantaneous wear rate is inversely proportional to the wear depth; (2) if corrosive vapors, such as fatty alcohols, are introduced into the environment, chemical reaction can limit the wear rate as a constant. In more complex situation, such as trifluoroethanol vapor, the rubbing process shows a transition from a short adhesive wear phase to a corrosive wear process. The thermal- and tribo-solvolysis could not give a full explanation of the life-time tests for the tested fatty alcohols. Therefore, there must be derivative reactions of grafting groups at silicon surfaces, which cause the instability of such groups. A mechanochemical mechanism is established to understand the stability of grafting groups in friction situation. Compared with fatty alcohols, fluoroalcohol is much more stable and can be used as vapor lubricant for Si-MEMS devices.

Biography:

After obtained his M.S. and Ph.D degrees in Mechanical Engineering at Kumamoto University, Japan, Dr. Yonggang Meng joined the State Key Laboratory of Tribology, Tsinghua University, in 1990. Since 1999, he has worked as a Professor at Tsinghua University. He has also worked temporally as a Visiting Scholar at City University of Hong Kong in 1997 and at University of Michigan, Ann Arbor, in 2001. His current research interests include: tribology of MEMS and hard disk drives, boundary friction mechanism and control, and tribological design of machine components. He is the author or co-author of over 120 peer-reviewed papers and 3 books. He also serves as an Editorial Board Member of the journals of Tribology Letters, Friction, and China Mechanical Engineering.

Time：10:00-11:30,March 1st,2013

Venue:1512#,YiFu Technology and Science Building