A TOUCH sensor developed to match the sensitivity of the human finger is set to herald the age of the robotic doctor.

Until now robots have been severely handicapped by their inability to feel objects with anything like the accuracy of their human creators. The very best are unable to beat the dexterity of the average six-year-old at tying a shoelace or building a house of cards.

But all that could change with the development by nanotechnologists of a device that can “feel” the shape of a coin down to the detail of the letters stamped on it.

The ability to feel with at least the same degree of sensitivity as a human finger is crucial to the development of robots that can take on complicated tasks such as open heart surgery.

Once the hurdle of touch is solved, robots have the potential vastly to increase their role in human society, whether as mechanical GPs, automated bomb disposal experts or astronauts who need not worry about getting back to Earth.

The touch device has been created by researchers in America who used nanoparticles to sense the contours of a coin. It is accurate enough to detect the outline of Abraham Lincoln’s face on a 1c coin and the letters TY in the word Liberty.

To make the sensor, the researchers built up a film consisting of alternate layers of gold and cadmium sulfide nanoparticles with a thin plastic sheet on top and glass below.

An object is placed on the plastic and an image sensor beneath the glass reads the changes in electrical current and electroluminescence caused within the nanoparticle layers.

The strength of the changes in electric charge and electroluminescence depends on how much pressure is being used. The more pronounced the shape on the coin, the stronger the signals emitted by the nanoparticles.

Analysis of the results, published in the journal Science, show that the sensitivity of the device is almost the same as that of a human finger.

Vivek Maheshwari and Ravi Saraf, of the University of Nebraska, say: “Variation in stress distribution caused by the embossing on a 1c coin leads to significant change in local current density.”

The ability to feel an object, whether a coin or a scalpel, would enable robots to improve their ability to grasp items. It would allow them to detect the texture of an item and judge whether it was slipping or being held so firmly that it was being squashed.

Richard Crowder, a senior lecturer at the School of Electronics and Computer Science at Southampton University, said the device could represent a breakthrough for robotics.

“Today’s state-of-the-art dextrous robotic hands cannot achieve tasks that most six-year-old children can do without thinking,” he said. “A key component needed for these new robots is the development of a sensor or set of sensors that can replicate the human sense of touch.”

He added: “The thin-film design permits the [researchers] to produce a single tactile sensor. The challenge is to extract the information efficiently — something the human nervous system does with supreme efficiency.”

One of the device’s big advantages over previous attempts at developing robotic touch, apart from the degree of sensitivity, is that it has the potential to be easy to use.

The nanoparticles are so thin, at 10 nanometres, that they can be brushed on to a surface such as a robotic finger without getting in the way.

They also have the potential for great durability because even if the film containing the particles gets torn, it can be quickly replaced with another.

Robots, once suitably dextrous, are widely regarded as having the potential for improving surgery because they would be more accurate. Nor would they sneeze during an operation.

Although a handful of basic “minimally invasive” medical procedures can be carried out by robots, their dexterity is too limited at present for them to be entrusted with more serious operations.

A robot that could feel the difference between healthy tissue and a cancerous tumour, however, would be an enormous step forward for medicine.

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