Design Rules
by | Jerry Fausz, Ph.D. |
[EDITOR’S NOTE: The following article was written by one of A.P.’s auxiliary staff scientists. Dr. Fausz holds a Ph.D. in Aerospace Engineering from Georgia Tech and serves as liaison to the NASA Marshall Space Flight Center. (All images in Dr. Fausz’ article are Courtesy of Sandia National Laboratories, SUMMiTTM Technologies, www.mems.sandia.gov.)]One of the most fascinating areas of modern engineering research is the development of what has become known as MicroElectroMechanical Systems, or MEMS. Imagine a closed-cycle steam engine no bigger than a pinhead that operates on a single drop of water (e.g., Frechette, et al., 2003, pp. 335-344), or mirror mechanisms for micro-optical systems with structures that can be obscured by a single dust mite (McWhorter, 2001; McWhorter, 2006). These devices are so miniscule that their operational performance has to be verified through a microscope. MEMS devices are used to actuate airbags in automobiles, precisely control optics in digital projectors and video cameras, and perform a variety of other functions (see “SAMPLES Program,” 2005; “MEMS Technology,” 2006). Yet, we have barely scratched the surface of possible applications for MEMS.
Spider mite on mirror assembly
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Thus, in the design, fabrication, and operation of MEMS devices, it is clear that “small” is not synonymous with “simple” or “easy to understand or fabricate.” As seen through the microscope, MEMS parts are easily as complex as their counterparts on the larger scale, if not more so. Furthermore, due to the strict requirements imposed by the meticulous fabrication process, the MEMS designer must exercise much more care in laying out the configuration of his design than would a designer working on a larger scale.
The incredible MEMS clutch mechanism. The miniscule
gears are 50 microns across. Keep in mind that there are 25,400 microns
to an inch.
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It is amazing that many of the engineers and scientists who have worked to make MEMS technology a reality believe that the vast, intricate, mechanical workings of the Universe, a Universe that appears to conform to immutable natural laws, came about through mostly random processes. They have witnessed the microscopic complexity of MEMS, yet they admit reasoning that suggests the galaxies, solar systems, planets, and stars evolved from “simpler” particles of matter that somehow came into existence at the beginning of time. They hold these beliefs in spite of their understanding of the painstaking process that is required to design and fabricate a single MEMS mechanism.
Fully-functioning MEMS transmission
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Up to about twenty years ago, it was thought that protons and neutrons were “elementary” particles, but experiments in which protons were collided with other protons or electrons at high speeds indicated that they were in fact made up of smaller particles. These particles were named quarks by the Caltech physicist Murray Gell-Mann, who won the Nobel prize in 1969 for his work on them.... So the question is: What are the truly elementary particles, the basic building blocks from which everything is made? (1988, p. 65).Since science so far has been incapable of even identifying the most elementary components of the Universe, it is unreasonable to conclude that “small” means simple or easy. Given this unexpected complexity at the sub-microscopic (quantum) level, it is incredible that otherwise reasoned thinkers would conclude that everything we observe resulted from random processes.
Close-up view of one vernier; the teeth are two microns wide and the spaces between them measure four microns.
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The performance observed in such a system (a bacterium) is so intricate and complex on such a small scale, that so far humans are incapable of duplicating it—MEMS is about as close as science has come to doing so. Yet, in stark contradistinction, many scientists seem to accept that a “simple” life form must have organized by accident and, in turn, given rise to all of the life that we observe on Earth.Because there are thousands of different enzymes with different functions, to produce the simplest living cell, Hoyle calculated that about 2,000 enzymes were needed with each one performing a specific task to form a single bacterium like E. coli. Computing the probability of all these different enzymes forming in one place at one time to produce a single bacterium, Hoyle and his colleague, Chandra Wickramasinghe, calculated the odds at 1 in 1040,000. This number is so vast that any mathematician would agree that it amounts to total impossibility.... [T]he total atoms in the observable universe are estimated to be only approximately 1080 (1997, pp. 58-59, emp. added).
Sitting atop some MEMS gears, this spider mite is the size of the period at the end of this sentence.
Complex MEMS ratchet mechanism
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The world’s smallest functioning triple-piston steam engine. One piston is five microns across or 1/5080 of an inch.
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Drive gear chain and linkages, with a grain of
pollen (top right) and coagulated red blood cells (top left, lower
right) to demonstrate scale.
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REFERENCES
Hawking, Stephen (1988), A Brief History of Time: From the Big Bang to Black Holes (New York: Bantam).
McWhorter, Paul (2001), “Intelligent Multipurpose Micromachines Made at Sandia,” Sandia National Laboratories, [On-line], URL: http://www.sandia.gov/media/micro.htm.
McWhorter, Paul (2006), MEMS Image Gallery, [On-line], URL: http://www.memx.com/image_gallery.htm.
“MEMS Technology” (2006), [On-line], URL: http://www.memx.com/technology.htm.
Overman, Dean (1997), A Case Against Accident and Self-Organization (Lanham, MD: Rowman & Littlefield).
“SAMPLES Program” (2005), Sandia National Laboratories, [On-line], URL: http://mems.sandia.gov/samples.
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