Medical Applications of Micro-Electro-Mechanical Systems (MEMS) Technology - Biomaterials Science: An Integrated Clinical and Engineering Approach - page 32

smart products by augmenting the computational ability of microelectronics
with the perception and control capabilities of microsensors and microactua-
tors. The integrated circuits can be thought of as the “brains” of a system, and
MEMS augments this decision-making capability with “eyes” and “arms,”
to allow microsystems to sense and control the environment. Microsensors
gather information from the environment through measuring mechanical,
thermal, biological, chemical, optical, and magnetic phenomena. The elec-
tronics then process the information derived from the sensors and through
some decision-making capability direct the microactuators to respond by
moving, positioning, regulating, pumping, and filtering, thereby control-
ling the environment for some desired outcome or purpose. Because MEMS
devices are manufactured using batch fabrication techniques similar to ICs,
unprecedented levels of functionality, reliability, and sophistication can be
placed on a small silicon chip at a relatively low cost. MEMS technology is
extremely diverse and fertile, both in its expected application areas and in
how the devices are designed and manufactured. Already, MEMS is revolu-
tionizing many product categories by enabling complete systems-on-a-chip
to be realized. MEMS is having a huge impact in medical applications, and
the number and diversity of MEMS applications in medicine is expected to
grow extremely quickly as the technology develops and matures.
Although major progress has been made in recent decades, the history of
MEMS technology traces back to the earlier days of the integrated circuit
industry. The discovery of the piezoresistive effect in silicon was reported
in 1954 by Prof. C. S. Smith, which led to the creation of the entire silicon-
based sensor industry. It is still one of the most widely used sensing method-
ologies in MEMS [2]. Perhaps the first and most far-reaching vision of the
promise of miniaturized electromechanical systems was provided in a talk
by Prof. Richard Feynman at an annual American Physical Society meeting
in 1959 aptly entitled “There's Plenty of Room at the Bottom” [3]. In this talk,
Prof. Feynman discussed many possibilities and opportunities of micro-
miniaturized devices, but since the microelectronics industry did not yet
exist, he did not foresee how these devices would be made and even ques-
tioned whether they would be commercially useful.
One of the first techniques of bulk micromachining, the isotropic etch-
ing of silicon, was reported in 1960 [4]. A few years later, in 1967, the still
widely used bulk micromachining technique of anisotropic silicon etch-
ing was reported [5]. The first published paper in the scientific literature
using the term micromachining was in 1982 [6]. This paper, entitled “Silicon
as a Mechanical Material,” published in the Proceedings of the IEEE by Kurt
Petersen, is probably the most referenced paper in the entire MEMS field and
highlighted many of the advantages of silicon as a material for mechanical
systems. In the 1980s and 90s, a huge number of papers and patents in the
MEMS technology domain occurred, and this growth has steadily contin-
ued to the present day. One of the first commercial MEMS products was
the micromachined pressure transducer using the piezoresistive properties