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Hearing aid to run on ear power
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Barnaby Hall/getty
FOR the first time, an electrical device has been powered by the ear alone. The technology uses a natural electrochemical gradient in inner ear cells, which in the future could power devices such as a hearing aid or brain implant. Nerve cells use the movement of positively charged sodium and potassium ions across a membrane to create a chemical gradient that drives neural signals. Hair cells in the cochlea use this gradient to convert the mechanical force of the vibrating eardrum into electrical signals that the brain can understand. A major challenge in tapping this electrical potential is that the voltage created is tiny – a fraction of that generated by an AA battery. Now, Tina Stankovic at Harvard Medical School in Boston and colleagues have developed an electronic chip containing low-resistance electrodes that can harness a small amount of that electrical activity without damaging hearing. The device was tested in a guinea pig, with the electrodes attached to both sides of the rodent’s cochlear hair cell membranes. Attached to the chip was a radio transmitter. After kick-starting the chip with radio waves, it sustained the low-power transmitter for 5 hours (Nature Biotechnology, doi.org/jqd).
18 | NewScientist | 17 November 2012
Jellyfish tentacles inspire clever cancer-catcher CANCER cells might evade the body’s defences, but dodging DNA tentacles is another matter. A jellyfish-inspired device might make it easier to diagnose cancer in its early stages. When people with conditions like leukaemia are in remission, it’s important to establish as early as possible whether their cancer has returned. Finding out involves passing a sample of blood through a microfluidic device, in whose tiny channels cancer cells can be captured and identified. However,
this only works well if blood passes through extremely slowly, so that any cancer cells bump into the channels’ sides, which are lined with adhesives designed to trap specific cells. This is time-consuming, and the method can also fail to spot cells at the early stages of cancer, when numbers are very low. So Jeffrey Karp at the Brigham and Women’s Hospital in Cambridge, Massachusetts, and colleagues have devised a better method – by following the lead of jellyfish. “We thought it would be
incredibly useful if we could mimic jellyfish and functionalise microfluidic devices with long tentacles,” says Karp. The tentacles are actually strands of DNA encoded to match an enzyme on the surface of leukaemia cells. The researchers found the strands trapped an average of 50 per cent of the cells, compared with 10 per cent using existing systems, and at a much faster flow rate. The tentacles also allowed for quicker collection of cancer cells for analysis (PNAS, DOI: 10.1073/pnas.1211234109). Danielle Dixson
Hearing aid to run on ear power
Tiny engine runs on hydrogen molecule POWER packs don’t get much smaller than this. The random movements of single hydrogen molecules have powered a tiny, vibrating springboard, mimicking molecular machines in nature. Heat from their surroundings causes all molecules to move randomly, but engineers tend to regard such movements as noise to be avoided like the plague. Jose Ignacio Pascual at the Free University of Berlin in Germany and colleagues took inspiration from the natural world, where random motion powers structures such as proteins that move cargo around inside cells. They placed a quartz springboard, weighing a fraction of a milligram, next to a slab of copper coated with hydrogen molecules. When a molecule changed its orientation, the force between the molecule and the board changed, setting the board vibrating. The team could keep the board vibrating by injecting electrons that encouraged the molecules to move, one at a time, in this way (Science, doi.org/jqg). “A single hydrogen molecule ends up pushing an oscillator 1019 times more massive than itself,” says Pascual.
Coral calls in the goby cavalry IT’S not quite the Bat-Signal, but it does the trick. A species of Fijian coral summons hungry gobies to rescue it from dangerous seaweed. When small staghorn corals are at risk of being smothered by mats of turtle weed, they send out a chemical distress signal. This calls the cavalry – in this case, broad-barred and redhead gobies – to come to their aid. The gobies eat the turtle weed, protecting the corals. Mark Hay at the Georgia Institute of Technology in Atlanta and colleagues placed the gobies in tanks with the turtle weed. They ignored it
until the coral was introduced, at which point they began eating (Science, doi.org/jp6). In return for eating the seaweed, the corals provide the gobies with shelter. Hay also found that the gobies’ skin secretions became more toxic to predators after eating the seaweed. “It really underscores how very little we know about biological interactions on coral reefs, even when processes so integral to the resilience of reefs are considered,” says John Pandolfi of the University of Queensland in Brisbane, Australia.
Barnaby Hall/getty
FOR the first time, an electrical device has been powered by the ear alone. The technology uses a natural electrochemical gradient in inner ear cells, which in the future could power devices such as a hearing aid or brain implant. Nerve cells use the movement of positively charged sodium and potassium ions across a membrane to create a chemical gradient that drives neural signals. Hair cells in the cochlea use this gradient to convert the mechanical force of the vibrating eardrum into electrical signals that the brain can understand. A major challenge in tapping this electrical potential is that the voltage created is tiny – a fraction of that generated by an AA battery. Now, Tina Stankovic at Harvard Medical School in Boston and colleagues have developed an electronic chip containing low-resistance electrodes that can harness a small amount of that electrical activity without damaging hearing. The device was tested in a guinea pig, with the electrodes attached to both sides of the rodent’s cochlear hair cell membranes. Attached to the chip was a radio transmitter. After kick-starting the chip with radio waves, it sustained the low-power transmitter for 5 hours (Nature Biotechnology, doi.org/jqd).
18 | NewScientist | 17 November 2012
Jellyfish tentacles inspire clever cancer-catcher CANCER cells might evade the body’s defences, but dodging DNA tentacles is another matter. A jellyfish-inspired device might make it easier to diagnose cancer in its early stages. When people with conditions like leukaemia are in remission, it’s important to establish as early as possible whether their cancer has returned. Finding out involves passing a sample of blood through a microfluidic device, in whose tiny channels cancer cells can be captured and identified. However,
this only works well if blood passes through extremely slowly, so that any cancer cells bump into the channels’ sides, which are lined with adhesives designed to trap specific cells. This is time-consuming, and the method can also fail to spot cells at the early stages of cancer, when numbers are very low. So Jeffrey Karp at the Brigham and Women’s Hospital in Cambridge, Massachusetts, and colleagues have devised a better method – by following the lead of jellyfish. “We thought it would be
incredibly useful if we could mimic jellyfish and functionalise microfluidic devices with long tentacles,” says Karp. The tentacles are actually strands of DNA encoded to match an enzyme on the surface of leukaemia cells. The researchers found the strands trapped an average of 50 per cent of the cells, compared with 10 per cent using existing systems, and at a much faster flow rate. The tentacles also allowed for quicker collection of cancer cells for analysis (PNAS, DOI: 10.1073/pnas.1211234109). Danielle Dixson
Hearing aid to run on ear power
Tiny engine runs on hydrogen molecule POWER packs don’t get much smaller than this. The random movements of single hydrogen molecules have powered a tiny, vibrating springboard, mimicking molecular machines in nature. Heat from their surroundings causes all molecules to move randomly, but engineers tend to regard such movements as noise to be avoided like the plague. Jose Ignacio Pascual at the Free University of Berlin in Germany and colleagues took inspiration from the natural world, where random motion powers structures such as proteins that move cargo around inside cells. They placed a quartz springboard, weighing a fraction of a milligram, next to a slab of copper coated with hydrogen molecules. When a molecule changed its orientation, the force between the molecule and the board changed, setting the board vibrating. The team could keep the board vibrating by injecting electrons that encouraged the molecules to move, one at a time, in this way (Science, doi.org/jqg). “A single hydrogen molecule ends up pushing an oscillator 1019 times more massive than itself,” says Pascual.
Coral calls in the goby cavalry IT’S not quite the Bat-Signal, but it does the trick. A species of Fijian coral summons hungry gobies to rescue it from dangerous seaweed. When small staghorn corals are at risk of being smothered by mats of turtle weed, they send out a chemical distress signal. This calls the cavalry – in this case, broad-barred and redhead gobies – to come to their aid. The gobies eat the turtle weed, protecting the corals. Mark Hay at the Georgia Institute of Technology in Atlanta and colleagues placed the gobies in tanks with the turtle weed. They ignored it
until the coral was introduced, at which point they began eating (Science, doi.org/jp6). In return for eating the seaweed, the corals provide the gobies with shelter. Hay also found that the gobies’ skin secretions became more toxic to predators after eating the seaweed. “It really underscores how very little we know about biological interactions on coral reefs, even when processes so integral to the resilience of reefs are considered,” says John Pandolfi of the University of Queensland in Brisbane, Australia.