Regular Article

The European Physical Journal B

, 85:377

Casimir attractive-repulsive transition in MEMS

  • M. BoströmAffiliated withDepartment of Energy and Process Engineering, Norwegian University of Science and TechnologyDepartment of Materials Science and Engineering, Royal Institute of Technology
  • , S.Å. EllingsenAffiliated withDepartment of Energy and Process Engineering, Norwegian University of Science and Technology
  • , I. BrevikAffiliated withDepartment of Energy and Process Engineering, Norwegian University of Science and Technology
  • , M.F. DouAffiliated withDepartment of Materials Science and Engineering, Royal Institute of Technology
  • , C. PerssonAffiliated withDepartment of Materials Science and Engineering, Royal Institute of TechnologyDepartment of Physics, University of Oslo
  • , Bo E. SerneliusAffiliated withDivision of Theory and Modeling, Department of Physics, Chemistry and Biology, Linköping University Email author 

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Abstract

Unwanted stiction in micro- and nanomechanical (NEMS/MEMS) systems due to dispersion (van der Waals, or Casimir) forces is a significant hurdle in the fabrication of systems with moving parts on these length scales. Introducing a suitably dielectric liquid in the interspace between bodies has previously been demonstrated to render dispersion forces repulsive, or even to switch sign as a function of separation. Making use of recently available permittivity data calculated by us we show that such a remarkable non-monotonic Casimir force, changing from attractive to repulsive as separation increases, can in fact be observed in systems where constituent materials are in standard NEMS/MEMS use requiring no special or exotic materials. No such nonmonotonic behaviour has been measured to date. We calculate the force between a silica sphere and a flat surface of either zinc oxide or hafnia, two materials which are among the most prominent for practical microelectrical and microoptical devices. Our results explicate the need for highly accurate permittivity functions of the materials involved for frequencies from optical to far-infrared frequencies. A careful analysis of the Casimir interaction is presented, and we show how the change in the sign of the interaction can be understood as a result of multiple crossings of the dielectric functions of the three media involved in a given set-up.

Keywords

Mesoscopic and Nanoscale Systems