Medical Applications of Micro-Electro-Mechanical Systems (MEMS) Technology - Biomaterials Science: An Integrated Clinical and Engineering Approach - page 34

board to the era of integrated circuits. Discrete electronics soldered onto
printed circuit boards do not have nearly the same level of high reliability
that is seen with integrated circuits. As miniaturized sensors and actuators
are integrated onto a single microchip with electronics, similar improve-
ments in system reliability are being provided by MEMS technology. For
example, MEMS inertial sensor technology used in crash airbag sensors for
automobiles is providing the extremely high reliability levels demanded by
this application. Obviously, most medical applications require exceptional
reliability, and MEMS technology is well suited to meet these demands.
Fourth, miniaturization of microsystems enables many benefits, includ-
ing increased portability, lower power consumption (very important for
implantable medical device applications), and the ability to place radically
more functionality in a smaller amount of space and without any increase
in weight.
Fifth, the ability to make the signal paths smaller allows the overall perfor-
mance of electromechanical systems to be enormously improved.
The largest growth area in medicine is in alternate care sites, including
off-site treatment centers, surgical centers, home care, nursing homes, and
ambulatory care. This is being driven by the need to reduce treatment costs as
well as improve patient comfort and outcomes. However, most alternate care
applications also require the medical devices to be less expensive, smaller, less
intrusive, more interoperable, lighter, safer, more user friendly, and more func-
tional than ever before. In short, MEMS is a technology that can simultane-
ously meet all of these demanding requirements in the medical device market.
How Are MEMS Made?
MEMS fabrication uses many of the same techniques that are used in the
integrated circuit domain, such as photolithography, physical vapor deposi-
tion, oxidation, diffusion, ion implantation, and LPCVD, and combines these
capabilities with highly specialized micromachining processes. The most
widely used micromachining processes are discussed below. For information
relating to integrated circuit fabrication techniques, readers are referred to [8].
Bulk Micromachining
The oldest micromachining technology is bulk micromachining. This tech-
nique involves the selective removal of the substrate material in order to
realize miniaturized mechanical structures and components. Bulk micro-
machining can be accomplished using chemical, physical, or mechanical
(as well as combinations of these) methods. However, chemical methods
are more widely used in MEMS industry.