Liquid lubrication may provide a solution to
the problem of high friction and wear in micro-electromechanical
systems. Although the effectiveness of this
approach has been demonstrated in laboratory-based friction
tests, practical constraints prevent it from being applied
in commercial devices. The main problem is how to
position the lubricant on a silicon surface in order to limit
spreading and evaporation. This paper describes two
techniques to address this issue. First, low concentrations
of additives are used to promote autophobic behaviour.
Tests’ results show that certain concentrations of both
multiply alkylated cyclopentane and amine additives are
effective in halting the spread of hexadecane on silicon,
and, in the latter case, cause the hexadecane drop to subsequently
retract. The second approach involves applying a
micro-contact printing technique previously used on gold
surfaces. Here, silicon surfaces are coated with octadecyltrichlorosilane
mono-layers that are then selectively removed,
using oxygen plasma, to leave regions of
contrasting surface energy. Results from spin tests show
that surfaces treated in this way can anchor 1 ll drops of
hexadecane and water when forces of up to 22 and 230 lN,
respectively, are applied.