Australasian Science: Australia's authority on science since 1938

Fooling Fingerprint Scanners Foiled

By Magdeline Lum

Magdeline Lum reports on quirky experiments and research findings.

Secret agents around the world have been dealt a blow in defeating fingerprint scanners. The days of cutting the finger off from their adversaries or fresh corpses to get into buildings, drive away in fancy cars or logging into a computer are over.

These may sound like scenes straight out of a spy movie, but in March 2005 an owner of a Mercedes S class equipped with a fingerprint protection system found himself the target of thieves. He was first kidnapped when the thieves stole his car to bypass the fingerprint-based security. The thieves decided soon after to cut off his finger before letting him go.

But Clarissa Hengfoss and her colleagues at Dermalog Identification Systems in Hamburg, Germany, have now developed an easy way for fingerprint scanners to tell the difference between a living finger and a severed digit. It is based on how living tissue changes colour, or “blanches”, when blood is squeezed out from capillaries. You can see this for yourself by pressing one of your fingertips to see the pink colour turn white. This difference can be measured.

Living fingers absorb LED light at 550 nm on the first contact with a surface and then at 1450 nm at full contact with a sensor when the skin is blanched. The fingers from three cadavers did not show any change in light absorbance. It is hoped that this will result in a fingerprint scanner that is not so easily fooled.

Diamonds Go Up in Smoke
A candle’s flame burns 1.5 million diamond nanoparticles every second. Yes, diamonds. Harvesting them is difficult at the moment but they are there ever so briefly as hydrocarbons at the base of the candle flame are converted to carbon dioxide found at the top of the flame.

Although candles have been around for just over 2000 years, (the earliest examples found in China dated to 200 BC), the components of a candle flame are much of a mystery.

Professor Wuzong Zhou from the University of St Andrews and his student Mr Zixue Su developed a sampling technique that collects particles from the centre of the candle flame. The duo created an ultrathin porous anodic aluminium oxide foil for the collection of soot particles in candle flames. The foil was 10 μm thin with 80 nm pores.

Prof Zhou and Mr Su collected four well-known carbon forms from within the carbon flame: graphite, fullerene, amorphous carbon particles and diamond particles. Any dreams of collecting the diamond nanoparticles quickly turn to ashes because the candle flame incinerates them all.

The discovery could lead to an efficient manner of creating diamonds without needing the high pressure and temperature techniques employed today. Further research into how the diamond nanoparticles form in a candle flame is needed.