In medicine, intuition is often required. That is why the relationship of trust with the family doctor is so important. Scientists are now preparing to let devices develop a similar sensitivity.
The cancer check-up, which every adult over the age of 45 should attend regularly, is not a pleasant thing for either the doctor or the patient. In the case of men, for example, the doctor, who is protected by a rubber glove, feels with a finger whether there are any suspicious hardenings in the abdomen of the person being examined.
Maybe at least the man in white will be able to escape this embarrassing procedure in the future and have it performed by a robot. Vivek Maheshwari of the University of Nebraska in Lincoln and Ravi Saraf of the Edward Via Virginia College of Osteopathic Medicine in Blacksburg may have thought so: They developed a wafer-thin film that is supposed to give artificial beings something like tact.
A difficult task, because the sensitivity with which our gripping tools can feel for bumps is amazing: Grooves, grooves or roughness on a smooth surface can still be felt down to a magnitude of a few thousandths of a millimeter. That is significantly less than the thickness of the finest downy hair of a small child. So far, attempts by technicians and engineers to achieve this sense of smell with technical aids have failed - with the result that they are able to design gripper arms for robots that may even be able to handle raw eggs. However, if the object gripped in this way slowly begins to slip and threatens to slide the artificial being through the pincers, the machine normally only notices this when the counter-pressure from the object it is trying to hold on to disappears from one second to the next. But then it's too late.
Therefore, the two scientists from the American research institutes came up with a thin foil that not only reacts very sensitively to pressure differences, but can also be pulled over a metal finger in order to equip it with a kind of sense of touch. The foil consists of alternating layers of nanometer-sized spheres of gold and cadmium sulfide separated by equally thin organic interlayers. The top gold electrode is also covered with a flexible plastic foil. A voltage of a few volts can be applied between it and the lower electrode made of transparent indium tin oxide, which was applied to a glass substrate for the laboratory experiments.
If you press a patterned object onto the foil from above, the bumps cause tiny, local currents that flow through the respective layers: the higher the pressure, the more current flows. This causes the cadmium sulphide to glow – a phenomenon that physicists refer to as electroluminescence. The higher the current, the brighter the light. The image that is created in this way can be transferred to a monitor with a CCD camera, which works in a similar way to a digital camera, or processed further electrically.
To convince themselves of the sensitivity of their invention, the developers pressed a one-cent coin with Abraham Lincoln's likeness onto their film. To their delight, they were able to identify the folds on the cape of the pictured former President of the United States.
Although it will hardly be possible to transfer this prototype of an optical touch finger to a gripper arm - the camera would take up too much space - the two scientists are sure that they can use this technology to construct a sensitive automaton. All they have to do is transmit the electrical signals directly to an electronic brain. The technology for this is already available, even if the resolution that can be achieved with it will probably deteriorate because even the finest wiring takes up more space than optical readout.
But nobody should wait until these gentle limbs come to the doctor's office. This may take some time. In any case, despite the inconvenience, you should not wait that long with the next cancer check-up. Until then, the examination is carried out in the conventional way, in which one stretches one's buttocks towards the doctor.