Tech

Blood-pressure-sensing underpants

Blood pressure is not hard to measure, but the necessary equipment for clinically accurate measurements - a cuff, a pump, and stethoscope or electronics - is bulky and heavy.

However, researchers have recently found that a person's "pulse wave velocity" is closely linked to blood pressure. This is the rate at which the pulse pressure wave passes through the blood circulatory system.

Sensors sewn into the waistband of a person's underpants can measure the rate of this wave, consumer electronics company Philips has discovered, and could be used to calculate blood pressure for as long as the garment is worn.

Each sensor continually measures the electrical impedance of the tissue beneath it - a property that changes as the pulse wave passes by. A pair of such sensors can calculate the speed of the pulse wave by timing how long it takes to travel from one sensor to the other.

Once calibrated with a conventional blood-pressure reading, the electrodes can then give accurate blood-pressure readings, while the wearer enjoys the comfort of their own underpants.

Read the full blood-pressure-sensing underpants patent application.

Bird-killing foam

Since 1999, there have been 26 avian influenza outbreaks in 25 countries, which resulted in the slaughter of more than 132 million birds.

With more outbreaks likely, killing such large numbers of poultry in a humane and efficient way that prevents any further spread of the disease is a significant problem.

One common method is to flood the birds' living areas with carbon dioxide. But although it is an avian anaesthetic, CO₂ also endangers humans. Now Eric Benson and colleagues at the University of Delaware in Newark have a potential answer.

They say that covering the birds with a blanket of CO₂-infused foam should quickly and humanely kill the birds with a minimal amount of manpower. And since the CO₂ is trapped within the foam, it should be relatively safe for humans.

Read the full humane bird-killing foam patent application.

Wallpaper speakers

Microphones and speakers use piezoelectric materials that move in response to voltage, or create voltage from movement. But common piezoelectric materials are expensive, heavy and brittle.

Now materials scientist Michael Yu at Johns Hopkins University in Baltimore and colleagues say they have made a rubbery plastic-based material that could help place piezoelectric devices in previously impractical areas.

The team's invention is based on a polypropylene foam with piezoelectric properties that was discovered in 2004. The plastic is flexible and has entirely different mechanical properties to most other, often crystalline or ceramic, piezoelectric materials.

By adding silicone rubber to that material, Yu and colleagues have made it possible to separately control the material's piezoelectric mechanical properties.

Until now changing the flexibility, say, of a piezoelectric material would always impact its electrical properties. That made it near-impossible to design materials with certain combinations of physical and piezoelectric properties.

Combined with the ease with which polymers can be processed, the new material should open up novel applications: wallpaper that functions as speakers, lightweight devices to scavenge movement energy, and foldable speakers, are just some of their ideas.

Read the full wallpaper speakers patent application.

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