MEASURING just half the width of a human hair, it could hardly be any smaller than the musclebound Terminator man-machine portrayed by Arnold Schwarzenegger. But when the tiny silicon robot flexed its muscles on the world stage this week it represented a gigantic breakthrough in the race to create a real cyborg.
The minute futuristic machine, just unveiled by scientists, crawls around courtesy of silicon "legs" powered by sugar-fuelled living muscle from a rat’s heart. It is the first time that experts have successfully used muscle tissue to propel a "micromachine" - bringing the evolution of cyborgs - part human, part machine just like Arnie’s Terminator or Seven of Nine from Star Trek Voyager, a crucial step closer.
And the musclebot, as the device is known, already has two heroic missions of its own worthy of any Hollywood blockbuster storyline.
Space agency Nasa - which funded the research project - hopes to send swarms of crawling musclebots into space to help maintain spacecraft by plugging holes made by tiny meteorites, potentially saving lives of astronauts and helping progress the ongoing space race.
Back on Earth, scientists believe that the microrobot could also be used to help paralysed people to breathe without the help of a ventilator by stimulating damaged nerves in their bodies. It would give countless patients the hope of a new lease of life.
The breakthrough is the result of three years of painstaking work by scientists at the University of California - ironically the state where the real-life Arnie is now governor. British cybernetics expert Professor Kevin Warwick, who famously became a cyborg for three months in 2002 when he had a microchip implanted in his arm to allow him to feel his way around using sonar, welcomes the advance.
"I don’t think Nasa would want to answer the question about it being a step towards creating a Terminator, but obviously it is. Arnie’s Terminator exemplified the way science fiction can make people think ‘could that happen in real life?’.
"This is tremendously exciting. When you are linking the brain or nervous system to a computer one of the problems is always the power supply. Using glucose from the body’s blood to power the device is a great idea, it uses the body’s energy."
He adds: "The fact that they say they have got this movement is, I think, significant. It could really move things forward, especially in terms of healthcare. It has a whole range of applications for people with paralysis. Not just in terms of breathing but also in terms of controlling things like bladder and bowel movements."
However he was a little scathing of the hopes of using the musclebots in outer space. "I think the ‘swarms of microrobots going into space’ is a bit too much like science fiction on Nasa’s part, calling it a robot is a bit over the top really," Warwick adds.
The science behind the breakthrough, which was reported this week in the respected scientific journal, New Scientist, is remarkable. Microengineer Carlos Montemagno and his research team created the musclebot by carving an arch-shaped "skeleton" just 50 micrometres wide (that’s five hundredths of a millimetre) from a wafer of silicon using specialist, automated microchip manufacturing equipment. They then placed the arch into a small laboratory dish containing rat heart muscle cells in a glucose culture.
But for three years they failed to find a way to encourage the muscle cells to grow on to the silicon skeleton to create the muscle-machine. The breakthrough came when they finally managed to develop a way of anchoring the muscle tissue to the silicon legs using a layer of gold film.
The gold film deposit acted as an adherent which the muscle cells could stick to, allowing them to grow into the silicon skeleton.
In the space of three days the muscle cells grew into muscle fibres which were able to attach themselves to the gold underside of the silicon arch, forming a cable of cardiac muscle running along the length of the arch.
While the muscle cells were growing, the structure was held in place by a restraining beam. Once the restraining beam was removed, however, the natural contraction and relaxation movements of the heart muscles made the arch bend and stretch - effectively making the musclebot start moving around in a crawling, crab-like motion - reaching speeds of up to 40 micrometres per second.
Scientists were amazed when they looked into their microscopes to see the latest version of the muscle-powered robot finally taking its first steps.
Although in the laboratory the muscle was fuelled by a glucose nutrient in a dish, scientists say that glucose deposits could be coated on to the surface where the robot was working to fuel it instead. That would give the musclebots an advantage over other micromotors which need electricity to function.
Montemagno hopes that the first application of the musclebot will be in helping patients whose nerves have been damaged through paralysis, leaving them to rely on ventilators to help them breathe. He believes the technology can be adapted to artificially stimulate the damaged nerves - known as phrenic nerves - which control the diaphragm muscle which in turn controls breathing.
Instead of moving the legs of the musclebot, the muscle fibres would be used to flex a piece of "piezoelectric" material and generate a tiny voltage to stimulate the nerve. By using cells from the patient’s own heart instead of a rat’s heart, Montemagno hopes to prevent the body’s natural impulse to reject the implant. He believes the muscle could be powered by glucose in the blood system.
Meanwhile Nasa hopes Montemagno will go on to fulfil his commission from the space agency’s Institute for Advanced Concepts to design a muscle-powered micromachine that could seek and repair meteorite punctures on spacecraft.
However, the scientist warns that such applications of the musclebot are several decades away. Speaking to the New Scientist, he says: "The issue of all of the microrobots talking to one another hasn’t even been addressed."
But this is undoubtedly the first step towards the possibility of creating cyborgs, an idea which has long fascinated the public - witness the popularity of the Terminator films. And scientists have gone to great lengths to try and turn the idea into reality.
Warwick began his first major experiment in cybernetics in August 1998, when he had a silicon chip transponder surgically implanted into his left arm. It allowed a computer to monitor his movements around a building, opening doors for him, switching on lights and even giving him a welcoming "hello" when he entered.
His arm did not reject the implant and there was no sign of infection. So in 2002 he became a cyborg for four months, having an implant of 100 silicon electrodes fired into his nervous system just below his left wrist.
With the implant in place, a direct radio connection was made between his nervous system and a computer network so that neural (brain) signals could be transmitted to the computer via the implant. As a result he was able to control a robot hand, make coffee, switch on lights and even drive a wheelchair around using only his neural signals.
Again there were no signs of infection. And Warwick reported that when the surgeon came to remove the implant, Warwick’s body tissues had grown round it, "as though my body didn’t want to let go of its new component, didn’t want to lose its new abilities now it had them. Human and machine had become one, a cyborg entity."
Today he is on a sabbatical from Reading University in Berkshire, at the University of Illinois, and he is optimistic about turning science fiction into science fact in the future. "I am going further in that direction, trying to make better connections between the human brain and a computer, for example, to look at controlling driving a car by thinking about it, or linking with memory to download and upload memories.
"It is like The Matrix film, where the guy had a big connection in the back of his neck. What I am working on is a mini version of that."
It might be Warwick, it might be Montemagno, or it might be someone else who finally brings a cyborg into the world. But one thing seems certain: they will be here.