ARTIFICIAL skin embedded with optical sensors could help robots develop a more human touch.
Existing sensors, such as those based on simple pressure switches and motor resistance, are limited in their ability to detect subtle changes in pressure and to distinguish between different textures. A key reason for this is the electrical components and wires they are made from tend to be inflexible.
Building in a lot of sensors will give a robot additional useful information about what it is touching and handling. However, placing large numbers of traditional sensors close together increases the potential for electromagnetic interference.
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To get around these obstacles, Jeroen Missinne and colleagues at Ghent University in Belgium have developed a flexible 鈥渟kin鈥� containing optical sensors.
The skin consists of two layers of parallel polymer strips lying perpendicular to each other to form a grid. These are separated by a thin sheet of plastic. Light is constantly fed into the polymer strips, which act like optical fibres in that their geometry encourages internal reflection and reduces light loss.
When pressure is applied anywhere on the skin it causes the strips to be pushed closer together and allows light to escape from one set into the other. The detection of this leakage of light provides a highly sensitive feedback mechanism.
鈥淲hen pressure is applied to the robot鈥檚 skin, light from one polymer strip escapes into another鈥�
Surgical robots are already able to provide some limited tactile feedback to surgeons. Missinne says this could be greatly enhanced if they were covered with his sensor-rich skin.
Because they are optical, neighbouring polymer strips do not interfere with each other, allowing them to be packed tightly together 鈥� as close as 125 micrometres so far.
鈥淲e鈥檙e desperate for new materials to let robots be able to feel the world,鈥� says Chris Melhuish of the Bristol Robotics Laboratory in the UK. It鈥檚 equally important, he says, that artificial skin gives a pressure reading that allows a robot to distinguish between different types of objects and different patterns of forces.
Missinne is hopeful that his skin can do this but has yet to prove it. He presented his latest findings, demonstrating that pressure triggers light to escape from one set of polymer strips to another, at the IMEC Flexible and Stretchable Electronics workshop in Ghent last week.
He is now working on developing a full prototype and hopes to begin more detailed tests by the end of the year.
