Hidden fingerprints can be made visible with chemical treatments aimed at molecules that are residual in fingerprints, like those in hair follicle secretions.
Xanthe Spindlerm who led a team of researchers at the University of Technology Sydney in Australia has developed a method to target amino acids in sweat and most fingerprints. Antibodies that created amino acid were connected to gold nanoparticles and applied to fingerprints. Red fluorescent secondary antibodies that would adhere to the nanoparticle-bound antibodies were used.
The technique builds on research at the University of East Anglia in the UK to create fingerprints from drugs residual in sweat, coating a nanoparticle with antibodies to identify all fingerprints.
The nanoparticle-based technique worked for prints taken a week earlier. Fresh fingerprints retain enough moisture to dissolve the amino acids and reagents wash them away. The fingerprint changes with age. Some components deteriorate with light and oxidation. But the amino acid does not change.