Sensing
Danger
by Ananya Mukundan
W
hen I presented my project on earthquake
detection at the Intel International Science and
Engineering Fair, people would ask me where I
live. “Michigan,” I would reply, and then would
come the inevitable second question: “How exactly did you think
of this project again?” After all, earthquakes are rare in Michigan,
and the most intense earthquake recorded there registered a magnitude of 4.6.
Quake Shake Network by Micah
Lidberg. This piece was created as
part of Intel’s SciArt project, which
paired artists with students at the
Intel International Science and
Engineering Fair. See the entire
series at sciart.intel.com.
But in recent years, earthquakes have been making news, from the devastating
earthquake in Haiti to the earthquake in Japan that caused a tsunami and led to
meltdowns in nuclear reactors. When I heard about these disasters, my first impulse
was to help the victims. Unable to travel to Haiti or Japan to physically help these
people, I thought of a way I could make a difference more broadly: science. More
specifically, I could try to develop an earthquake detection device that would prevent
or minimize this kind of suffering in the future.
The Theory
The Earth’s crust comprises 13 major plates and several minor plates that
meet at fault lines. These plates do not move quickly—their movement is
measured in millimeters annually—but being of massive size, even small
movements can cause a large amount of force to be released. When there is a
sudden release of energy built up along the fault lines, there is an earthquake.
The U.S. Geological Survey estimates that millions of earthquakes occur
every year, although most are not detectable or occur in areas where they
are not felt and therefore not recorded.
For years, scientists have searched for an accurate method of predicting
earthquakes. Some methods have involved monitoring magnetic fields, water
flow beneath the surface, and changes in electrical conductivity of materials
beneath the surface. However, the most reliable warning system today can
provide only four to five seconds of lead-time, and that is only for places
kilometers away from the epicenter of the earthquake.
I started my research by scouring online journals looking for any ideas
that I might be able to develop. I came across the theory that fluctuations
in the Earth’s magnetic field might occur hours or even days before an
earthquake. Recently, scientists have begun using magnetometers, devices
that can measure the strength and direction of a magnetic field, to test
this theory.
Existing magnetometers are capable of measuring changes in magnetic
fields on the scale of 10 to 100 nanoTesla (nT), which is not precise enough
to rule out environmental noise. The only existing device precise enough
to measure what would be a minute change in the Earth’s magnetic field is
called a SQUID magnetometer; however, because it uses liquid nitrogen, it
operates only at extremely low temperatures and would thus not be practical
for use in the field.
I decided to create a device that could precisely sense extremely small
changes in magnetic field and that could operate at room temperature. I was
going to need some help.
The Method
I applied to the Army Research Office High School Apprenticeship Program,
which places high school students in university labs, specifying my preference to work in a physics lab. I was fortunate to be matched to a physics lab
at my local university, Oakland University, where I worked with Dr. Gopalan
Srinivasan. It was my good fortune that this lab was doing research in magnetics. Almost immediately I discussed my ideas with Dr. Srinivasan, who
was open to my pursuing this work in his lab.
Over the next six weeks, I developed a sensor made up of two components: a magnetostrictive part and a piezoelectric part. A magnetostrictive
material is one that changes dimension when exposed to a changing magnetic field, and a piezoelectric material is one that produces an electrical
charge when it is deformed (twisted or stretched). The magnetostrictive and
piezoelectric materials available to me—Metglas and PZT, respectively—
were not the most effective materials of their kind, but they were the only
ones the laboratory was able to give me, so I had to try to make them work.
The Metglas and the PZT components were connected with an epoxy
binder. The idea was that when the device was exposed to a changing
magnetic field, the Metglas portion would change its dimensions, causing
the PZT portion to change shape and thus produce a measurable voltage.
To test it, I placed the device between two Helmholtz coils, which produce a uniform magnetic field. I then used an electromagnet to create a
change in the magnetic field. The sample was connected to an oscilloscope,
which measured the voltage generated when the field changed. I tested
samples with different configurations of piezoelectric and magnetostrictive
layers to find the one that would produce the highest voltage. The sample
made of one piezoelectric layer with five magnetostrictive layers on both
sides produced a voltage on the order of 100 millivolts. Using this device,
I was able to measure small magnetic field changes on the order of 0.1 nT.
I had done it: This was a sensor that worked at room temperature and
might be sensitive enough to detect changes in the Earth’s magnetic field.
The Reward
My weeks working in the lab were some of the best experiences I have ever
had. It was an amazing feeling to succeed in what I’d set out to do, and it was
thrilling to present my work at ISEF, where I won a prize from the Society of
Exploration Geophysicists. Winning that prize, standing on that stage, was
an experience I had never dreamed of.
My research project was just one step in a much longer process that would
be necessary before the device could be operational. This system would have
to be tested in the field, using a series of sensors near earthquake-prone
regions, such as parts of California. I would have to find a way to measure the
voltage signal produced by the device in the field (vs. the controlled field of
the lab) and then devise a way to transmit the signal to an earthquake detection center. Finding the resources to field test this device will be difficult, and
I am still not certain whether I will pursue this myself.
But I am certain that I will continue to be involved in research. That
feeling of achievement was an incredible high, yet even more rewarding was
the idea that a device I had created could possibly be used to save lives.
Ananya Mukundan is a freshman at the University of
Michigan, where she is studying biophysics. In addition
to conducting scientific research, which takes up a large
portion of her time, Ananya is an ardent volunteer. She
is also interested in humanities and the arts, especially
linguistics and vocal music.
Learn more about the High School Apprenticeship Program at www.usaeop.com/programs/HSAP.
Learn more about the Intel ISEF at www.societyforscience.org/isef.
www.cty.jhu.edu/imagine
imagine 17