A high-aspect-ratio two-axis electrostatic microactuator with extended travel range

Yu Sun, D. Piyabongkarn, A. Sezen, B. J. Nelson, R. Rajamani

Research output: Contribution to journalArticlepeer-review

63 Scopus citations


The design, fabrication, modelling, and control of a two-axis electrostatic microactuator for precision manipulation tasks is described. A high-yield fabrication process using deep reactive ion etching (DRIE) on silicon-on-insulator (SOI) wafers forms the 3-D high aspect ratio transverse comb drives that produce a relatively large electrostatic force. The structure is suspended by removing the substrate beneath the comb drives, therefore, a ground plane is not needed in order to compensate for electrostatic levitation. Among other advantages of the developed process is a dice-free release of wafer structures, allowing fragile structures to be individually packaged. Notching or footing effects and bowing effects are well-known problems in DRIE on SOI wafers. Techniques to overcome notching and bowing effects using a PlasmaTherm SLR-770 etcher are presented that do not require hardware modifications. A capacitive position sensing mechanism, capable of measuring displacements up to 4.5 μm with a resolution of 0.01 μm in both X and Y is integrated to provide position feedback. A nonlinear model inversion technique is proposed for nonlinear electrostatic microactuation system identification and improving system linearity and response. Pull-in instability limits the travel distance of transverse comb drive actuators. Using a nonlinear model inversion technique, a stable travel distance of 3.7 μm with a 4.5 μm gap has been achieved.

Original languageEnglish (US)
Pages (from-to)49-60
Number of pages12
JournalSensors and Actuators, A: Physical
Issue number1-2
StatePublished - Dec 1 2002

Bibliographical note

Funding Information:
B.J. Nelson is the Mayhugh associate professor of Mechanical Engineering at the University of Minnesota. He received the BS degree in Mechanical Engineering from the University of Illinois at Urbana-Champaign in 1984, the MS degree in Mechanical Engineering from the University of Minnesota in 1987, and the PhD degree in Robotics (School of Computer Science) from Carnegie Mellon University in 1995. He has been an assistant professor at the University of Illinois at Chicago, has worked as an engineer for Honeywell Inc. and Motorola Inc., and has served as a United States Peace Corps Volunteer in Botswana, Africa. He has been awarded a McKnight Land-Grant Professorship and is a recipient of the Office of Naval Research Young Investigator Award, the National Science Foundation Faculty Early Career Development (CAREER) Award, and the McKnight Presidential Fellows Award. At the University of Illinois he was awarded the Bronze Tablet, the highest award for academic achievement offered by this institution. His research interests include biomedical engineering, computer vision, controls, manufacturing, mechatronics, MEMS, microrobotics, robotics. His most recent scientific contributions have been in the area of microrobotics, including efforts in robotic micromanipulation, microassembly, MEMS, mechanical manipulation of biological cells and tissue, and nanofabrication.

Funding Information:
R. Rajamani obtained his MS and PhD degrees from the University of California at Berkeley in 1991 and 1993, respectively, and his B.Tech degree from the Indian Institute of Technology at Madras in 1989. After obtaining his PhD, Dr. Rajamani spent 5 years working as a Research Engineer first at United Technologies Research Center (UTRC) and then at California PATH. Since September 1998, Dr. Rajamani has been Nelson assistant professor in the Department of Mechanical Engineering at the University of Minnesota. His active research interests include control design and state estimation for nonlinear systems, fault diagnostics, intelligent transportation systems, active noise control and MEMS sensor design. Dr. Rajamani has authored over 40 refereed publications and received two patents. He has won several awards including the CAREER award from the National Science Foundation, the 2001 Outstanding Paper award from the journal IEEE Transactions on Control Systems Technology, the Distinguished Service Team Award from the University of California, Berkeley and the Outstanding Achievement of the Year award from United Technologies Research Center.


  • DRIE
  • Electrostatic actuation
  • Microactuator
  • Nonlinear control
  • SOI


Dive into the research topics of 'A high-aspect-ratio two-axis electrostatic microactuator with extended travel range'. Together they form a unique fingerprint.

Cite this