This microscopic scale and sensitivity allows the sensor to map a high-resolution image of electrical charge that occurs over the surface of a source material (for example a human finger), when it makes contact with a thin insulating surface (ie a plastic surface).

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"Personally, I think that having some threshold would give some more uniformity to the test, but pragmatically we don't want to limit the sensitivity of tests, " said Prof David Cowan from King's College London, who is in charge of anti-doping at next summer's London Olympic Games.

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