Rap Music Powers Rhythmic Action of Medical Sensor

This graphic illustrates the principles behind the operation of a new type of miniature medical sensor powered by acoustic waves, including those found in music such as rap, blues, jazz and rock. The device, a pressure sensor, might ultimately help to treat people stricken with aneurisms or incontinence due to paralysis. (Credit: Birck Nanotechnology Center, Purdue University)

The driving bass rhythm of rap music can be harnessed to power a new type of miniature medical sensor designed to be implanted in the body.

Acoustic waves from music, particularly rap, were found to effectively recharge the pressure sensor. Such a device might ultimately help to treat people stricken with aneurysms or incontinence due to paralysis.

The heart of the sensor is a vibrating cantilever, a thin beam attached at one end like a miniature diving board. Music within a certain range of frequencies, from 200-500 hertz, causes the cantilever to vibrate, generating electricity and storing a charge in a capacitor, said Babak Ziaie, a Purdue University professor of electrical and computer engineering and biomedical engineering.

"The music reaches the correct frequency only at certain times, for example, when there is a strong bass component," he said. "The acoustic energy from the music can pass through body tissue, causing the cantilever to vibrate."

When the frequency falls outside of the proper range, the cantilever stops vibrating, automatically sending the electrical charge to the sensor, which takes a pressure reading and transmits data as radio signals. Because the frequency is continually changing according to the rhythm of a musical composition, the sensor can be induced to repeatedly alternate intervals of storing charge and transmitting data.

"You would only need to do this for a couple of minutes every hour or so to monitor either blood pressure or pressure of urine in the bladder," Ziaie said. "It doesn't take long to do the measurement."

Findings are detailed in a paper to be presented during the IEEE MEMS conference, which will be Jan. 29 to Feb. 2 in Paris. The paper was written by doctoral student Albert Kim, research scientist Teimour Maleki and Ziaie.

"This paper demonstrates the feasibility of the concept," he said.

The device is an example of a microelectromechanical system, or MEMS, and was created in the Birck Nanotechnology Center at the university's Discovery Park. The cantilever beam is made from a ceramic material called lead zirconate titanate, or PZT, which is piezoelectric, meaning it generates electricity when compressed. The sensor is about 2 centimeters long. Researchers tested the device in a water-filled balloon.

A receiver that picks up the data from the sensor could be placed several inches from the patient. Playing tones within a certain frequency range also can be used instead of music.

"But a plain tone is a very annoying sound," Ziaie said. "We thought it would be novel and also more aesthetically pleasing to use music."

Researchers experimented with four types of music: rap, blues, jazz and rock.

"Rap is the best because it contains a lot of low frequency sound, notably the bass," Ziaie said.

The sensor is capable of monitoring pressure in the urinary bladder and in the sack of a blood vessel damaged by an aneurism. Such a technology could be used in a system for treating incontinence in people with paralysis by checking bladder pressure and stimulating the spinal cord to close the sphincter that controls urine flow from the bladder. More immediately, it could be used to diagnose incontinence. The conventional diagnostic method now is to insert a probe with a catheter, which must be in place for several hours while the patient remains at the hospital.

"A wireless implantable device could be inserted and left in place, allowing the patient to go home while the pressure is monitored," Ziaie said.

The new technology offers potential benefits over conventional implantable devices, which either use batteries or receive power through a property called inductance, which uses coils on the device and an external transmitter. Both approaches have downsides. Batteries have to be replaced periodically, and data are difficult to retrieve from devices that use inductance; coils on the implanted device and an external receiver must be lined up precisely, and they can only be about a centimeter apart.

A patent application has been filed for the design.

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The above story is reprinted from materials provided by Purdue University. The original article was written by Emil Venere.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Climate action could save polar bears

HANGING ONSustainable populations of polar bears might be possible in shrinking Arctic sea ice after all, new research suggests.Steven C. Amstrup/Polar Bears International

Cutting greenhouse gas emissions enough over the next few decades may stabilize the rapidly shrinking Arctic sea ice sufficiently to provide a sustainable habitat for polar bears, a paper in the Dec. 16 Nature reports. And if emissions do keep rising, another new study finds, the only species that has officially been declared threatened by the U.S. government due to global warming may still be able to hang on for a while in a few pockets of the northern Arctic.

Polar bears need sea ice to hunt their prey, but the frozen skin that floats atop the Arctic Ocean has been thinning and shrinking in recent decades as global temperatures rise. Between 1979 and 2010, Arctic sea ice cover at the end of the summer melt season dropped an average of 11.5 percent per decade. Many researchers think that end-summer Arctic ice could be almost entirely gone by the middle of this century.

In 2007, the U.S. Geological Survey reported that two-thirds of the world’s 25,000 polar bears could disappear within 50 years if greenhouse gas emissions continued unabated. The following year, interior secretary Dirk Kempthorne relied on that report when putting the bear, Ursus maritimus, on the government’s list of threatened species.

Steven Amstrup, an Anchorage-based senior scientist with Polar Bears International in Bozeman, Mont., who was a coauthor on the 2007 USGS report, decided to look at whether cutting emissions could preserve enough of the Arctic sea ice to save polar bears from extinction.

In the Nature paper, his team studied five scenarios for how much atmospheric levels of greenhouse gases would rise over the next century.

Using a widely accepted climate model, the researchers analyzed potential futures for several measures of sea ice habitability — such as the amount of sea ice extending over continental shelves, the number of months each year those shelves are free of ice and the distance between that ice and the more northerly pack ice that bears also use to hunt.

The results don’t support the idea that Arctic sea ice is headed for a catastrophic “tipping point” beyond which the ice disintegrates completely, Amstrup says. Instead, if greenhouse gas emissions and hence temperatures can be stabilized, the sea ice stabilizes too.

“If we act, it isn’t too late to save the polar bear,” Amstrup says.

As it thins, sea ice reaches a point where it becomes more responsive to the water temperature below and is better able to regrow in the winter , says Marika Holland, a sea ice specialist at the National Center for Atmospheric Research in Boulder, Colo. This enhanced growth helps stabilize the shrinking ice.

Still, the more people can limit greenhouse gas emissions, the less melting will happen in the first place, says Amstrup.

Even if emissions keep rising, sea ice will stick around in certain areas of the Arctic longer than others, Stephanie Pfirman, an Arctic specialist at Barnard College in New York and the nearby Lamont-Doherty Earth Observatory, and her colleagues will report in San Francisco December 16 at the annual meeting of the American Geophysical Union. The work meshes nicely with the new Nature paper, she said: “They’re asking what happens if we act to mitigate. We’re looking at the base case: What if we don’t act?”

Winds and ocean circulation regularly pile ice up in the Canadian Arctic archipelago and north of Greenland, Pfirman said. Sea ice is thick there today and may persist long after it has melted elsewhere, the researchers propose.

Polar bears aren’t the only creatures that may depend on those last remnants of ice cover, Pfirman noted. An entire ecosystem, including seals and walruses, depends on sea ice. On December 3, the National Oceanic and Atmospheric Administration proposed listing four subspecies of ringed seal and two populations of bearded seal as threatened because of shrinking ice. It is the first such proposal since the polar bear based solely on the threat of climate change. 

By 2100 only the northern fringes of Canada and Greenland — the same areas Pfirman’s group identified in its polar bear study — will have snow deep enough to shelter ringed seal pups, suggests research presented at the AGU meeting by Brendan Kelly, a marine-mammal specialist at NOAA’s National Marine Mammal Laboratory in Juneau, Alaska, and Cecilia Bitz, a sea ice physicist at the University of Washington in Seattle. Each spring, these seals make snow caves atop the ice to shelter their newborn pups; to do so, they need snow at least 50 centimeters deep.

But in a greenhouse world, these high Arctic pockets will last only so long, says Robert Newton, an oceanographer at Lamont-Doherty.

“This [refuge] is not expected to last forever,” Newton says. “As the planet keeps warming, it will eventually be lost.”

Back Story | Where the bears are

The International Union for Conservation of Nature puts polar bears into 19 subpopulations. Shown are estimated numbers of bears in 15 of the groups with years of the estimates

Credit: GeoAtlas/Graphi-Ogre, adapted by E. Feliciano

Found in: Climate Change, Earth, Ecology and Environment

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