1. Department of Mechanical and
Industrial Engineering, University of Illinois at Chicago, Chicago, Illinois 60607, United States
2. Department of Mechanical Science
and Engineering, Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana−Champaign,
Urbana, Illinois 61801, United States
3. Department of Mechanical Engineering, North Dakota State University, Fargo, North Dakota
58102, United States
4. Department
of Electrical and
Computer Engineering, Micro and Nanotechnology Laboratory, University of Illinois at Urbana−Champaign,
Urbana, Illinois 61801, United States
5. Korea Research Institute of Standards and Science, Daejeon 305-340,
Republic of Korea
6. Department of
Physics and Astronomy, Seoul National University, Seoul 151-747, Republic
of Korea