Robot hits the right vein

The robot is claimed to be more reliable than humans

Taking blood can be an inaccurate science and sometimes health professionals dig the needle in too deep, causing painful bruising.

But a robot nurse could be the answer.

Scientists at Imperial College in London have developed a robot that can take blood samples.

They claim it is more reliable than a human being.

The robot finds the patient's vein by gently prodding parts of the arm and recording the force which bounces off the tissue.

The scientists say it can tell what lies underneath the skin with an accuracy of one millimetre.

Alex Zivanovic, a mechanical engineer working on the project, said veins had a different feel to muscle and fat.

Muscle is hard, fat is soft and veins feel "like an underinflated balloon", he said.

Once it has found the veins, the robot displays their location on a screen.

Human operator

It suggests which is the most appropriate place to put the needle in, but it is down to its operator to make the final decision.

As the needle enters the patient's skin, the robot uses strain gauges to monitor whether it is causing any injury.

If the wall of the vein is broken, the robot immediately stops work.

Tony Firth, an anatomist at Imperial College, told New Scientist that this safeguard was particularly flexible since it meant the robot did not assume all patients' veins were the same size or depth.

This makes it useful for finding veins in children and obese people.

David Keeling, a consultant haemotologist at the Oxford Haemophilia Centre, said it could also help people who faced a lifetime of receiving injections, such as diabetics, by identifying new veins.

"If you are sticking a needle in the same veins, you can get inflammation, thrombosis and the vein can become occluded," he said.

But he added that there could be difficulty getting children to sit still.

Artificial limbs

And Alex Zivanovic admitted many patients might be put off by having their blood taken by a robot, unless the safety aspect was properly explained.

He hopes eventually to develop a robot which can operate without the help of a human.

The robot still has a way to go before it is used on humans. So far, it has only been tested on artificial limbs used to train medical students.

These mimic the layering of skin and even contain artificial blood.