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Magnetic ‘battery’ to report on nuclear waste after 100 years
TECHNOLOGY
Sticky feet send insect-bot climbing up the walls as a robot walks. The grooves lead to the creation of more fluid bridges between the foot and surface than occur with a smooth foot. This makes the pads 50 per cent more adhesive, according to Li’s mathematical models. This design may help Li resolve
Magnetic ‘battery’ to report on century-old nuclear waste DEALING with radioactive waste is a pressing problem, and if deeply buried repositories are ever built to store it we will need to know what is going on inside them many years after they are sealed. So, with funding from the UK nuclear industry, engineers at the University of Bristol have come up with an answer: a “battery” that uses a magnetic spring to create the necessary power to send a message from a repository to the outside world 100 years on. The device will be crucial because getting mains electricity into such 24 | NewScientist | 26 February 2011
their footpads to stick to surfaces. The hairs bend on contact with the surface, and the intermolecular van der Waals force causes the two to stick together. These hairs have been mimicked in the lab using carbon nanotubes. So far, gecko-bots, such as the Stickybot developed by Mark Cutkosky and his team at Stanford University in California, are winning the race to the top as they can scale vertical walls, while Li’s insect-bot can’t handle inclines over 75 degrees. However, geckobots struggle on rough, wet or salty surfaces, as water and salt can interfere with van der Waals forces, says Kellar Autumn of Lewis & Clark College in Portland, Oregon, who studies gecko adhesion and how to apply it to robots. Not only that, but making hairs that are both ultra-thin and bendy is difficult. As nanotubes get thinner, they also become stiffer and the force needed to bend them means larger motors are required, resulting in bigger robots. Li’s work is preliminary and gecko-bots have their own challenges, says Autumn, but combining the adhesion methods of insects and geckos could one day lead to the ultimate sticking –Aiming high– machine. Sujata Gupta n Minghe Li/Tongji University
AN OPEN window hundreds of metres up in a sheer glass tower block. No machine could reach it, surely? Step forward an insect-bot, with sticky feet that help it climb. All insects squirt a sticky fluid from their feet as they walk. This creates a liquid “bridge” between foot and surface, forming a strong glue-like bond through surface and molecular tension. Minghe Li, a roboticist at Tongji University in Shanghai, China, is trying to replicate this effect to create the next generation of climbing robots. He has designed an insect-bot that releases a mixture of honey and water onto its feet when it wants to climb. This fluid creates the liquid bridges favoured by insects. But the prototype has not been as successful as an insect. So Li took another look at insects, such as stick insects, and saw they also have grooves on their feet, which enhance their sticking power. Li is now replicating these grooves in a silicon foot pad etched with hexagons that spread out when pressure is applied
another problem he has with his groove-free prototype: getting the robot to secrete the sticky fluid slowly enough. Insects release a nanometre-thick layer of fluid, but Li’s robot currently releases large droplets. He hopes the grooves will spread the droplets more evenly across the footpads. Li’s insect-bot faces stiff competition from robots modelled on another climber: the gecko. Instead of relying on sticky fluid, geckos use millions of hairs on
sealed dumps will not be allowed – the wiring channels might let flood water in, or radioactive matter out. And a chemical battery would be flat long before the first century is up. The novel power source comprises a 15-centimetre-long carbon-fibre rod which has a powerful neodymium magnet at each end. A third, doughnut-shaped magnet is free to move along the rod, which is surrounded by a copper coil. To “set” the battery, the mobile magnet is forced against one of the fixed magnets, whose poles are arranged to repel each other, and locked into place
with a latch that can be released by a timer. The magnet at the other end of the rod attracts the mobile magnet. After 100 years, a timer releases the latch – and the repelled mobile magnet springs quickly past the coil to strike the attracting magnet. As it does so, electromagnetic induction creates a small current in the coil, just enough to charge a bank of
“Power generation could be triggered by a radio signal or an ultra-reliable clockwork mechanism” capacitors. That power is used to run checks on wireless temperature and radiation sensors via a radio signal – and to transmit the data out of the facility via an antenna (Sensors
and Actuators, DOI: 10.1016/j. sna.2010.12.005). Making a 100-year timer is a challenge. Peter Constantinou, on the Bristol team, says the latch could be triggered by a radio signal from outside – or an ultra-reliable clockwork mechanism could be developed. “This invention sounds like the sort of idea we need to look into,” says John Dalton of the UK’s Nuclear Decommissioning Authority. Doug Parr, chief scientist at Greenpeace in the UK, is unimpressed. “Spent fuel remains hazardous for 240,000 years. It’s good to see there’s a possibility of monitoring for the first 100 years – that just leaves the other 99.96% of the time to worry about.” Paul Marks n
Sticky feet send insect-bot climbing up the walls as a robot walks. The grooves lead to the creation of more fluid bridges between the foot and surface than occur with a smooth foot. This makes the pads 50 per cent more adhesive, according to Li’s mathematical models. This design may help Li resolve
Magnetic ‘battery’ to report on century-old nuclear waste DEALING with radioactive waste is a pressing problem, and if deeply buried repositories are ever built to store it we will need to know what is going on inside them many years after they are sealed. So, with funding from the UK nuclear industry, engineers at the University of Bristol have come up with an answer: a “battery” that uses a magnetic spring to create the necessary power to send a message from a repository to the outside world 100 years on. The device will be crucial because getting mains electricity into such 24 | NewScientist | 26 February 2011
their footpads to stick to surfaces. The hairs bend on contact with the surface, and the intermolecular van der Waals force causes the two to stick together. These hairs have been mimicked in the lab using carbon nanotubes. So far, gecko-bots, such as the Stickybot developed by Mark Cutkosky and his team at Stanford University in California, are winning the race to the top as they can scale vertical walls, while Li’s insect-bot can’t handle inclines over 75 degrees. However, geckobots struggle on rough, wet or salty surfaces, as water and salt can interfere with van der Waals forces, says Kellar Autumn of Lewis & Clark College in Portland, Oregon, who studies gecko adhesion and how to apply it to robots. Not only that, but making hairs that are both ultra-thin and bendy is difficult. As nanotubes get thinner, they also become stiffer and the force needed to bend them means larger motors are required, resulting in bigger robots. Li’s work is preliminary and gecko-bots have their own challenges, says Autumn, but combining the adhesion methods of insects and geckos could one day lead to the ultimate sticking –Aiming high– machine. Sujata Gupta n Minghe Li/Tongji University
AN OPEN window hundreds of metres up in a sheer glass tower block. No machine could reach it, surely? Step forward an insect-bot, with sticky feet that help it climb. All insects squirt a sticky fluid from their feet as they walk. This creates a liquid “bridge” between foot and surface, forming a strong glue-like bond through surface and molecular tension. Minghe Li, a roboticist at Tongji University in Shanghai, China, is trying to replicate this effect to create the next generation of climbing robots. He has designed an insect-bot that releases a mixture of honey and water onto its feet when it wants to climb. This fluid creates the liquid bridges favoured by insects. But the prototype has not been as successful as an insect. So Li took another look at insects, such as stick insects, and saw they also have grooves on their feet, which enhance their sticking power. Li is now replicating these grooves in a silicon foot pad etched with hexagons that spread out when pressure is applied
another problem he has with his groove-free prototype: getting the robot to secrete the sticky fluid slowly enough. Insects release a nanometre-thick layer of fluid, but Li’s robot currently releases large droplets. He hopes the grooves will spread the droplets more evenly across the footpads. Li’s insect-bot faces stiff competition from robots modelled on another climber: the gecko. Instead of relying on sticky fluid, geckos use millions of hairs on
sealed dumps will not be allowed – the wiring channels might let flood water in, or radioactive matter out. And a chemical battery would be flat long before the first century is up. The novel power source comprises a 15-centimetre-long carbon-fibre rod which has a powerful neodymium magnet at each end. A third, doughnut-shaped magnet is free to move along the rod, which is surrounded by a copper coil. To “set” the battery, the mobile magnet is forced against one of the fixed magnets, whose poles are arranged to repel each other, and locked into place
with a latch that can be released by a timer. The magnet at the other end of the rod attracts the mobile magnet. After 100 years, a timer releases the latch – and the repelled mobile magnet springs quickly past the coil to strike the attracting magnet. As it does so, electromagnetic induction creates a small current in the coil, just enough to charge a bank of
“Power generation could be triggered by a radio signal or an ultra-reliable clockwork mechanism” capacitors. That power is used to run checks on wireless temperature and radiation sensors via a radio signal – and to transmit the data out of the facility via an antenna (Sensors
and Actuators, DOI: 10.1016/j. sna.2010.12.005). Making a 100-year timer is a challenge. Peter Constantinou, on the Bristol team, says the latch could be triggered by a radio signal from outside – or an ultra-reliable clockwork mechanism could be developed. “This invention sounds like the sort of idea we need to look into,” says John Dalton of the UK’s Nuclear Decommissioning Authority. Doug Parr, chief scientist at Greenpeace in the UK, is unimpressed. “Spent fuel remains hazardous for 240,000 years. It’s good to see there’s a possibility of monitoring for the first 100 years – that just leaves the other 99.96% of the time to worry about.” Paul Marks n