In its most common definition, the field of
microelectromechanical systems (or MEMS) encompasses tiny (generally
chip-scale) devices or systems capable of realizing functions not
easily achievable via transistor devices alone. Among the useful
functions realized via MEMS are:
1)
Sensing of various parameters that include
inertial variables, such as acceleration and rotation rate; other
physical variables, such as pressure and temperature; chemicals,
often gaseous or liquids; biological species, such as DNA or cells;
and a myriad of other sensing modes, e.g., radiation.
2)
Control of physical variables, such as the
direction of light (e.g., laser light), the direction of radiated
energy, the flow of fluids, the frequency content of signals, etc.
…
3)
Generation and/or delivery of useful
physical quantities, such as ultra-stable frequencies, power, ink,
and drug doses, among many others.
Although useful, the above definition and
functional list fall short of describing some of more fundamentally
important aspects of MEMS that allows this field to accomplish
incredible things. In particular, MEMS design and technology
fundamentally offer the benefits of scaling in physical domains
beyond the electrical domain, to additionally include the
mechanical, chemical, and biological domains. We are all well aware
of the benefits of scaling when applied to integrated circuits.
Specifically, via continued scaling of dimensions over the years,
integrated circuit transistor technology has brought about
transistor-based circuits with faster speed, lower power
consumption, and larger functional complexity than ever before. All
of these benefits have come about largely through sheer dimensional
scaling.
By scaling the features of devices that operate
in other physical domains (e.g., mechanical), MEMS technology offers
the same scaling benefits of
1)
Faster speed, as manifested by higher
mechanical resonance frequencies, faster thermal time constants,
etc., as dimensions are scaled.
2)
Lower power or energy consumption, as
manifested by the smaller forces required to move tiny mechanical
elements, or the smaller thermal capacities and higher thermal
isolations achievable that lead to much smaller power consumptions
required to maintain certain temperatures.
3)
Higher functional complexity, in that
integrated circuits of mechanical links and resonators, fluidic
channels and mixers, movable mirrors and gratings, etc., now become
feasible with MEMS technology.
Unfortunately, although scaling does bring about
significant benefits, it can also introduce penalties. For example,
although miniaturization of accelerometers lowers cost and greatly
enhances their g-force survivability, it also often results in
reduced resolution—a drawback that must be alleviated via proper
design strategy. This course will examine the pros and cons of
scaling via MEMS technology, with a specific focus on the physical
principles, tools, and methodologies needed to properly model MEMS
devices and concepts to the point of being able to identify methods
for maximizing the advantages while suppressing any drawbacks.
There
will be two hour-and-a-half lectures and a one-hour discussion
session per week. The lectures will be supplemented by reading
assignments (indicated on the COURSE SYLLABUS), additional reading
material to be distributed throughout the course, problem sets (at
the rate of one per week, occasionally per two weeks), one midterm
exam, a project, and a final exam. Although the material covered in
the lectures and in the reading is fundamentally the same, the
perspectives differ, and you are all strongly encouraged to both
attend the lecture and complete your reading assignments.
Furthermore, there will be occasional announcements in lectures that
will affect your problem sets and exams.
Lectures and
Discussion, 4 credit hours.
