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524 CAM DESIGN HANDBOOK

Shuttle
mass

FIGURE 15.14. Schematic of the electrostatic comb-
drive.

15.7.3 Sandia’s Microengine

What is called a microengine by Sandia researchers is essentially an electrostatic comb
drive with a linkage to convert reciprocating translational motion to continuous rotation.
It is schematiclly shown in Fig. 15.15. Some of the revolute joints in this original design
were subsequently replaced with flexible joints in later designs. The microengine is micro-
fabricated using Sandia’s SUMMiT process. It is a very successful microactuator and its
use has been demonstrated in a number of applications, some of which are described in
Sec. 15.6. Additionally, it has enabled Sandia researchers to conduct extensive experiments
to understand failure mechanisms at the microscale.

15.7.4 Other Actuators
Numerous actuation techniques have been attempted at the microscale. It would not be an
overstatement to say that every conceivable physical and chemical phenomenon that can
be miniaturized using accessible microfabrication processes has been attempted. Kovacs
(1998) contains good descriptions of most of them. The majority of the actuators devel-
oped have been demonstrated to move themselves but often do not have the force or torque
to move the components connected to them. For transducer-type applications and optical
applications, this is adequate. When substantive mechanical transmission becomes more
prevalent, actuators will need to be greatly improved.