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CAMS IN MICROELECTROMECHANICAL SYSTEMS 527

15.9 SUMMARY

This chapter began by stating that the scope of cams has somewhat expanded to include
gears and ratchets and other types of devices that involve intermittent and sustained contact
between rigid bodies. The main reason for this is the limited applications where sophisti-
cated mechanical motions are required. This has to do with the evolution of the MEMS
field, where the emphasis has been on microtransducers (sensors and actuators). The
slower development of MEMS applications involving mechanical transmission may also
be due to the limited capabilities of micromachining techniques compared to the
macroscale machining techniques. As the need for mechanical transmission at the
microscale increases, linkages, gears, and cams will appear as much as beams and mem-
branes do at present. It is also possible that future developments involving mechanical
manipulation might require compliant mechanisms where there is no relative rigid-body
motion but complex motions are not precluded. At this juncture, it is important to note
that nature seems to avoid sliding contacts at the microscale and prefers compliant designs
where there are only elastic deformations. However, engineered designs can overcome the
limitations and make sliding contacts more viable even at the microscale. Whether rigid-
body motions are good or elastic deformations are good definitely depends on a number
of factors. These factors include materials, manufacturing processes, and an understand-
ing of friction and wear and how to overcome them at the microscale.

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