Serendipity in Engineering
Many inventions have come about accidentally. This is the case in Engineering as well as
other areas of research. Many such
famous cases of serendipity include the discovery of penicillin, sticky notes,
play-doh, crazy-glue, and others. Some
engineering inventions have come about by serendipity as well. Two will be discussed here: smart dust or MEMS (Micro-electromechanical
Systems) and Microwave ovens.
Smart Dust or MEMS (Micro-electromechanical Systems).
Smart Dust are small silicon based devices about 1 cubic
millimeter in size. Smart Dust, also
called MEMS (Micro-electromechanical systems), function as sensors, robots or
other micro-electromechanical devices that detect physical properties such as
light, temperature, chemicals, magnetism, or vibration (Hsu, Kahn, and
Pister, 1998). Hence, the device is useful in analyzing
physical, chemical, or biological systems.
I.e., the devices interface between the electronic world and the
physical world. The "electro"
part is the electronic sensor and processing of the sensed data, and the
mechanical part is the sensor's interface to the physical property. They communicate the data about the physical
attribute they are sensing wirelessly to a computer, where the sensed information
is further analyzed (Kahn, Katz, and Pister, 1999). Sensing is often done through radio frequency
identification. A smart dust system may
be one cubic millimeter in size. Berkeley
is working on a one cubic millimeter MEMS that includes a programmable
microprocessor, a bidirectional optical communications system, a sensor, a
power supply, and analog to digital conversion (Pister, Kahn, and Boser, 1999).
Potential applications of smart dust systems include the
following. A smart dust camera is
possible with a lens 120 millionths of a meter, which takes high resolution
photographs. This is due to the light
sensing capability of some MEMS devices.
3D printing of a circuit for such a small camera is possible. The lenses are composed of strands of optical
fiber. Such small cameras could do
medical imaging inside the body and even in the brain, not to mention the use as
spy cameras or for use as security cameras. MEMS that sense chemicals can be
used to detect tumors or biological agents.
The Accidental
Discovery
The systems were originally discovered by Jamie Link, an
electronics graduate student at U.C. Berkeley in an accident. Jamie accidentally destroyed a silicon chip
she was working on, and upon further investigation noticed that some of the
resulting pieces still functioned as sensors.
Berkeley and the Department of Defense (DARPA) worked on the devices to
develop them into usable products.
Forces Driving the MEMS Technology
There are several drivers of this technology. First of all, the medical community is in
dire need of ways to do medical imaging within the body that are non-invasive
and non-destructive. Applications such
as tumor detection, detection of plaque build-up in the arteries, brain imaging
for cancers and other neural damage are all critical. The micro-sensors could have applications in
meteorology with the ability to sense differences in pressure and temperature
and light. Various defense related
applications are driving the technology, such as battlefield sensing,
particularly the ability to sense chemical or biological agents, hence the
interest of DARPA and DOD in this technology.
Another application driving MEMS is package tracking in inventory
control and shipping. These small
communications devices could be embedded in packages and could automatically
communicate with the internet about their whereabouts without any scanning
involved. Another commercial use would
be product quality monitoring, including monitoring the physical attributes of
food (to insure freshness and edibility) or electronics products (to insure
they were not exposed to destructive temperatures or moisture). Medical devices could be practically invisible, for example a
micro-hearing aid.
Microwave Ovens
Microwaves and Microwave
Technology.
A microwave is an electromagnetic wave within the frequency
of 10^8 cycles per second to 10^12 cycles per second (Hz). A cycle refers to the rise and fall of one
sine wave. I.e., every form of
electromagnetic energy has a frequency associated with it measured in Hertz or
cycles per second. This rise of energy
and fall of energy is cyclical and follows the form of a sine wave. The crest of one sine wave to the next is one
cycle. Microwave radiation is invisible. It is somewhat slower than infrared light
which is also invisible. Visible
electromagnetic radiation (colors) range from 3.8 * 10^14 to 7.5 * 10^14
cycles. Radio waves are even slower than microwaves at 10^4 cycles per second
to 10^8 cycles per second. We all know
that radios broadcast audible signals. Radar,
which Percy Spencer was working on, normally uses radio waves. However, some radar systems use higher
frequency waves like microwaves. There
is a whole engineering science behind microwave communications. Microwave communications systems usually work
using electromagnetic waves (carrier waves) between 1 GigaHertz (1 * 10^9
cycles per second) and 300 GigaHertz (1 * 10^11 cycles per second). Microwave communications now carry wireless computer
data, television signals, and telephone signals over medium to long distances
through point to point connections or satellites. It is in investigating microwave radar that
Percy Spencer noticed that the microwave systems generated heat.
The Accidental
Discovery
In 1945, the self taught engineer, and many thought
engineering genius, Percy Spencer, was working on microwave radar systems for
Raytheon. While operating one of the
microwave communications systems, Percy Spencer noticed that his pants were
getting hot. Furthermore, he noticed
that a chocolate bar that he had in his pocket melted. Quick to realize the potential of this side
effect of microwave systems, he convinced Raytheon to get a patent on a
microwave oven. Although this invention
was patented in 1945, it was not until 1967 that the real microwave oven
revolution took off.
Microwave Ovens and
Microwave Oven Technology
Microwave ovens warm food by passing microwaves at the
frequency of 2.4 gigahertz (2.4 billion cycles per second) in residential
kitchens. In industrial installations a
915 megahertz (915 million cycles per second) microwave is typically used. These frequencies are different than
microwave communication devices use so as not to interfere with those
signals. Food heated in a microwave oven
uses dielectric heating, as the heated microwaves move through the food and
excite its molecules. Food in a
microwave heats from the inside out versus traditional cooking which heats from
the outside in. A consumer microwave uses 1100 watts of electricity to create
700 watts of microwave energy, the rest being dissipated as heat (Risman, 2009).
A microwave uses a Faraday cage to prevent microwaves from coming out of
the oven. Microwaves include various
controls to control the amount of microwave energy produced and hence the
cooking time.
Forces Driving the
Microwave Oven Revolution
Home Cooking
Amana produced a portable microwave oven that could go in
everyone's kitchen in 1967. The systems
in 1955 were too big to be marketable. The
invention and patent of a microwave oven in 1945 by Raytheon long preceded the
microwave oven revolution that occurred in the 60's. The microwave oven technology had to be
miniaturized and productized.
In the 1950's when television was all of the rage, TV
dinners became popular. But these had to
be cooked in conventional ovens. The
desire for a quick hot meal or snack, i.e., microwave meals or snacks, was
already there. This was one of the main
drivers for microwave ovens.
In 1967, when residential microwave ovens became possible,
there was a virtual overnight revolution.
Everyone was buying a microwave oven.
The convenience could not be matched.
Soon food products further drove microwave oven sales: frozen microwave ready to eat meals and
snacks.
Restaurant Cooking
Microwaves are not used extensively in commercial cooking,
as cooks discourage the use of microwaves in favor of other heat sources such
as a gas flame. However almost every
commercial kitchen does have a microwave or two.
Industrial Applications
There are various industrial uses for microwave ovens.
Cooking and Heating in Space.
Microwave ovens are used extensively in space. You cannot create a flame in zero oxygen, and
even in the oxygen rich environment of a space capsule or station, you wouldn't
want to have a flame. Hence, heating is
typically done by microwave.
Conclusion
Two examples of serendipity of engineering inventions have
been discussed here: smart dust or MEMS
and Microwave Ovens. The accidental
discovery of these two inventions was covered as well as the technicalities
involved in both types of products.
References
Accidental Inventions:
http://gizmodo.com/5620910/whoops-the-10-greatest-accidental-inventions-of-all-time
Hsu, V., Kahn, J. M.,
and Pister, J. (1998). "Wireless Communications for Smart
Dust", Electronics
Research Laboratory Technical Memorandum Number M98/2, February.
Kahn, J.M., Katz, R., and Pister, J. (1999). "Mobile Networking for Smart Dust",
ACM/IEEE Intl. Conf. on Mobile Computing
and Networking (MobiCom 99), Seattle, WA, August.
Pister, J., Kahn,
J.M., and Boser, B.E. (1999). "Smart
Dust: Wireless Networks of Millimeter- Scale
Sensor Nodes", Highlight Article in 1999 Electronics Research Laboratory Research Summary.
Risman, P. (2009). "Advanced
topics in microwave heating uniformity", pp. 76-77, in, M W Lorence, P S Pesheck (eds), Development
of Packaging and Products for Use in Microwave
Ovens, Elsevier, 2009
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