Abstract:
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The present thesis is meant to be part of the research project ‘Slippery when dry –
Eliminating friction on the nanoscale’ from TU Delft 3mE PME department, leadered by W.
M. van Spengen and in cooperation with F. Buja.
Concerning the research project as a whole, MEMS/NEMS (micro-/nano-electromechanical
systems) are small, moving mechanical microstructures, like micromotors, accelerometers
and chemical sensors. Although there have been scientific and commercial successes,
reliability problems related to friction and wear prevent designers from taking full advantage
of this technology. In this project, we will use a two-pronged approach towards solving friction
and wear in MEMS: 1. the use of diamond-like carbon (DLC) coatings, and 2. films formed by
vapour phase lubrication (VPL). Some DLC films macroscopically show almost vanishing
friction (‘superlubricity’), which is not well understood. However, at the scale of MEMS,
superlubric DLC has not been demonstrated. VPL involves carbon-containing molecules that
condense between the contacting points of sliding surfaces and form a hard tribofilm. The
basic physical principles are believed to be the same for the tribological behaviour of both
DLC and VPL. It should be possible to induce superlubricity using VPL instead of DLC by
tailoring the molecular composition of the vapour. This would be the best of both worlds,
because VPL has the advantage over a DLC layer that it can be applied more easily in many
complex MEMS devices.
Since this research project requires making measurements with different devices in order to
understand the friction on the nanoscale, the present thesis will focus on the resolution of
such devices. Raman spectrometer and MEMS comb drive are examples of devices whose
noise level can be studied, although the noise background theory is applicable to other kind
of measurements. |