A door knocked off its hinges. Furniture in disarray. A billowing
curtain, masking an open window. A crime scene - complete with murder
victim. But whodunnit?
Dusting for prints may seem like the
obvious next step, but a new method may literally shed light on the
culprit. Research led by Bin Su
at Zhejiang University in Hangzhou, China, uses a type of luminous glow
known as electrochemiluminesence (ECL) to make fingerprints show up.
Prints are currently detected using a physical or chemical "developer", for example powder dusting
or chemical fuming. These methods rely on the fingerprint absorbing and
reacting with this developer, destroying or altering the print itself.
Non-destructive methods are better, but more expensive. Su and
colleagues suggest a method for identifying prints that is
non-destructive and could potentially be used on fingerprints whether
they are fresh or old, complete or smudged.
Rather than highlighting the print itself, this method instead lights up
the background surface, producing a negative image of the fingerprint. This clearly
shows not only the ridge pattern, but also fine details like the
branching and ends of lines, as well as the distribution of sweat pores,
says Su. The technique could also be used to hunt for evidence of
illegal drug use.
ECL is produced in solutions during chemical reactions, or can be
generated in a lab. By applying a voltage to a conducting material such
as steel, electrons become excited. They form compounds in this excited
state and then lose energy, emitting light - ECL - as they drop back
down to their original state.
Su's method is limited by the need for prints to be on a conducting
material. However, the researchers are working on methods to collect and
transfer prints from any surface using ECL.
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