Thank Wired-Up it’s Friday!

This week we are looking at sneaky science.  Fingerprinting, forensics and fiendishly-identifiable fluids.  So whodunnit? Who stitched up Pluto? It seems that its planet-ishness has been called into question. How very dare you!  Read on and see what you think.

1. The Wire – How round is your planet?
2. You What?  – SmartWater, the latest security device
3. Planet Picks – how to become a forensic scientist
4. Try This! – Sticky fingers
5. Gear for Grabs – Fingerprint Detective Tube

Have you heard of SmartWater?  No it’s not some fancy new sports drink, it’s a security method. It acts a bit like a security marker.  You know when you write your postcode on your belongings and it can only be read under ultraviolet light?

SmartWater is a liquid containing uniquely numbered micro-dot particles. The smallest amount is sufficient for identification under a microscope. There are millions of combinations, each uniquely coded and licensed to an individual. A bit like DNA. Codes are held on a secure database.

Its unique forensic fingerprint is almost invisible to the naked eye. It fluoresces under ultraviolet light, and is virtually impossible to completely remove. Particles will remain on clothing indefinitely and can stay on the skin for weeks.  Criminals coming into contact with SmartWater can instantly be connected to the crime. Amazing eh?  Forensic science just gets better and better.

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Fingerprints – whodunnit?

You will need:

• Fingers + friends' fingers
• An assortment of drinking glasses - make sure they're clean!
• Cocoa powder
• A small artists' brush
• A magnifying glass
• An inkpad
• White paper - one sheet per person

What to do:

1. Give everybody a glass and a sheet of paper.
2. Get each person to make a finger or thumb mark on the rim of the glass.
3. Once they've done this, the detective work starts. Swap glasses, being careful to touch only the base of the glass. Don't smudge the prints that are already there!
4. Examine each glass for fingerprints. Using the brush, place a small amount of cocoa over where the prints were made.
5. Use the brush to lightly dust over the prints to help make them a bit clearer.
6. On sheets of paper, get each person who left a print originally to make another print - but this time they have to press their finger or thumb in the inkpad first.
7. Match these new prints to the ones you duster for earlier. Use the magnifying glass to help you inspect them even more closely and try to match them up.
8. See if you can name the 'culprit' who left their prints on each glass. When you've had enough, wash and dry the glasses, and start again!

What’s happening:

No two fingerprints are the same; even twins will have differences in their prints.

When you examine a print you'll notice the lines occur in one of three characteristic patterns, known in the biz as 'arches', 'loops' and 'whorls'.

When you come to compare the chocolate and the ink prints you should get an exact match between pairs. But although two different people may have the same fingerprint type (e.g. both have loops on the same finger), there will always be other little differences between individuals. That's because it's not the shape of the print that's unique, but rather the number, location and shape of specific ridge characteristics...

What you were lifting with the cocoa powder are called 'latent' prints. These prints are formed by oil and sweat from a person's fingers when they touch a surface - the sweatier you are the clearer they'll be! They're invisible to the naked eye, which is why they need the dusting to help you see them...

Another method of taking your prints is to scribble on a piece of paper with a pencil then rub your finger over the scribble.  You should now have a nice grey fingertip! Now carefully take a piece of sticky tape and press the sticky side over your fingertip.  As you slowly peel it off you will see a very clear fingerprint stuck to it.  Stick this fingerprint down onto a white piece of paper. The features are very obvious, aren’t they?

If this has made you want to try more then look at the Creative Chemistry site.

There’s also a printable worksheet suitable for younger scientists in Dynamo's Lab on the BBC Education website.

Happy printing!

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