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Wednesday, July 17, 2013

new fingerprint collection technique

Instead of focusing on the residue itself, Robert Hillman and colleagues at the University of Leicester, the Institut Laue-Langevin (ILL) and ISIS at the Rutherford Appleton Laboratory have decided to work with the bare surface between the ridges of a fingerprint. "Think of the deposits on the surface to be like little 'hills', we've decided to go for the bare metal at the bottom of the 'valleys'," explains Hillman.

Recently, the team has been experimenting with an electrochromic polymer that changes colour when an electrical voltage is applied. "We used electrochemistry to deposit a polymer from a monomer solution and subsequently we replaced the monomer deposition solution with a background electrolyte," explains Hillman. The invisible residue left by a human finger does not conduct electricity, so it acts like a stencil. When the polymer is deposited on a fingerprint and the voltage is applied, the sticky deposit blocks the current, directing the film to the "valleys" in between the "hills". The voltage changes the film's colour, optimizing the visual contrast and essentially creating a negative image of the print.