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12/06/2007
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Devices to help people with disabilities are getting ever more sophisticated. Lou Reade reports
For people ‘locked in’ with conditions such as ALS, their only contact with the outside world is via sophisticated technology – such as eye-tracking systems that help them spell letters out one at a time. But at an advanced state of deterioration their eye muscles stop working – rendering the system useless.
So scientists have begun to develop systems that bypass the senses and tap directly into the brain. A number of devices can now ‘read’ brainwaves, allowing ALS sufferers to communicate once again. The cost of these systems is often around $25,000 (£12,500) – far beyond the reach of most people. But one team of engineers has managed to develop such a system for just $5,000 (£2500).
“The US Medicare system will reimburse up to $5,000 – so that was our aim,” says Mark Manasas, a project manager at Cambridge Consultants in the US.
The device works by detecting an involuntary ‘surprise’ response called the P300 response – which produces a tiny voltage spike in the brain. On a viewing screen, letters are arranged into a grid, then each rows or column is lit up briefly
“Every time ‘your’ letter flashes, there is a tiny P300 response which can be detected,” says Manasas.
Removing so much cost from the system has meant many compromises – but accuracy has been maintained, says Manasas. The system uses EEG sensors to detect brainwaves, in the form of electrical impulses on the scalp. The sensors are embedded in a ‘cap’ worn by the patient. The skill is in amplifying the voltage spike into a meaningful digital signal.
“We’ve looked at a number of amplifier configurations,” says Manasas. “To take this to the next level we would need to create an active electrode, which would give a better signal.”
Future development depends on funding, and there are moves to try and set up a non-profit organisation to take it further. Possible areas of development include: using more sophisticated EEG sensors; and making the sensors semi-invasive by penetrating 50 microns into the skin – where conductivity is higher.
Physical assistance
From a low-cost brain scanner to high-cost prosthetics: several manufacturers believe that the market is ripe for sophisticated prosthetic limbs that are more responsive to the needs of the user.
An example is the iLimb, a ‘bionic hand’ developed by Scottish company Touch Bionics. The company recently demonstrated the hand, which has five individually powered digits including jointed fingers and rotating thumb. A full commercial launch is expected within months.
While its £2500 price tag is comparable with that of the brain-computer interface, this is still around twice the price of a conventional prosthetic device.
Myoelectric sensors mounted on the skin collect muscle-generated electrical signals and feed them through to the hand, which is capable of three types of grip – precision, ‘key grip’ and power grip. One patient, who used the hand in a trial, recently used it to pick up a pint of beer for the first time in 30 years.
The hand itself, made from high temperature nylon from DuPont, incorporates several motion components: a central controller; a carbon Kevlar drive belt, which provides grip force along the whole finger; a non back-drive gearbox, ensuring that a grip is fixed in position; and a motor in each individual finger.
Meanwhile, Iceland-based Ossur has developed similar prostheses for the knee and foot. Its Proprio Foot – priced as high as £9000 – claims to be the world’s first motor-powered, intelligent prosthetic foot.
A series of accelerometers sample the foot more than 1,000 times per second to determine its position in space. The angle of the ankle and toes are then adjusted using a set of actuators to ensure a more natural stride. For example, the toes are curled upwards as the leg swings forwards,
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Author
Tom Shelley
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