INTRODUCTION - In levitated MEMS structures, like rotating gyroscopes or micromotors, large surface areas of two parts get into contact, e.g. a rotor and stator in a currently inactive device. Permanent adhesion, i.e. sticking between such parts, might lead to total system failure. For the design of levitated structures, systematic investigations of the adhesion and especially of the pull-off forces for lifting the structures into a levitated state are of great importance. In this context surface geometry and material's selection are key-issues to overcome the adhesion problem.
- In this study we investigate two different approaches for the
measurement of pull-off forces: The first experiment is performed with passive
structures. Here the adhesion energy is determined by the Weibull-type
distribution statistics of sticking occurrence and mechanical
of the investigated structures. The second experiment is performed with
active structures which allow for a direct measurement of applied pull-off forces.
FIGURE - (A) SEM recording of a silicon disc supported by 3 silicon oxide springs. The top surface of the silicon disc is one of the contact surfaces for the adhesion energy measurement. (B) SEM photograph of a Silicon disc supported by four polymeric springs. The structures are part of an active measurement device for the measurement of pull-off forces. (C) Microscope photograph showing the electrode pattern of an electrostatic bearing
|D. Bachmann and C. Hierold, "Determination of pull-off forces of textured silicon surfaces by AFM force curve analysis," Journal of Micromechanics and Microengineering, vol. 17 pp. 1326-1334, 2007.||URL PDF4|
|D. Bachmann, S. Kuhne, and C. Hierold, "MEMS scanning mirror supported by soft polymeric springs and actuated by electrostatic charge separation," in Technical Digest of IEEE 20th Annual International Conference on Micro-Electro-Mechanical-Systems, MEMS 2007, January 21-25, Kobe, Japan, pp. 723-726, 2007.|
|D. Bachmann, S. Kuhne, and C. Hierold, "Determination of the adhesion energy of MEMS structures by applying Weibull-type distribution function," Sensors and Actuators A: Physical, vol. 132, pp. 407-414, 2006.||URL PDF3|
|D. Bachmann, S. Kühne, and C. Hierold, "Novel Measurement Method for Characterization of Adhesion in Levitated MEMS Structures," in Proceedings of the EUROSENSORS XIX, September 11-14, Barcelona, Spain, 2005.|
|D. Bachmann, B. Schoberle, S. Kuhne, Y. Leiner, and C. Hierold, "Fabrication and characterization of folded SU-8 suspensions for MEMS applications," Sensors And Actuators A-Physical, vol. 130, pp. 379-386, 2006.||URL PDF3|
|D. Bachmann, S. Kuhne, and C. Hierold, "Fabrication process of polymeric springs for MEMS applications," in Digest of Technical Papers of the 2005 International Conference on Solid State Sensors, Actuators and Microsystems (Transducers2005), June 5-9, Seoul, Korea, pp. 1416-1419, 2005.|
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