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See Inside August 2006

Alight Touch

Modern state-of-the-art fingertip-size sensors for touch are sensitive enough to detect features only about two millimeters wide. Chemical engineers at the University of Nebraska—Lincoln have now made sensors that reach the micron range, rivaling the delicacy of human touch. They fabricated a 100-nanometer-thick sheet of alternating self-assembled layers of gold and cadmium sulfide nanoparticles separated by insulating films. Once a voltage is applied through the film, pressure on it causes electrons to tunnel from the gold through the insulating films to the cadmium sulfide layers, which then glow. Images developed from this light capture features 40 microns wide and five high, detailed enough to show the wrinkles on Lincoln's clothing on a penny. Future touch sensors for robots based on this work will most likely rely not on light signals but rather on electrical impulses, researcher Ravi Saraf explains. The findings appear in the June 9 Science.

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