Security marking
Last updated: September 4, 2008.
Hands off, it's mine! If you've spent a long time earning the money to buy something nice—a flashy car, a shiny laptop, a whizzy camera, or whatever it might be—the last thing you want is for someone else to make off with it. But trying to stop people stealing the things you own is never easy. Science is brilliant at solving everyday problems like this, so how can it help us this time? Let's look at some of the ingenious technologies people have developed for stopping thieves in their tracks!
Photo: Mark your property with microscopic identification dots or invisible ink and you'll stand a much better chance of getting it back.
Marking your property with fluorescent ink
The best intruder alarm in the world can't always keep thieves out of your home and if your valuables get stolen they're often gone for good. Even if the police catch the crooks and recover some of their loot, how can they ever return it to its rightful owners? Who knows which camera or TV belongs to which person? Science offers a really easy solution! All you have to do is mark your property with an invisible, fluorescent ink that shows up only in ultraviolet light. When the police recover stolen property, they wave an ultraviolet lamp over it, the markings (maybe your name or zip code) show up, and they instantly find out to whom it belongs.
Photo: Ultraviolet lamps like this can be used to show up the "invisible" security inks that deter thieves. Photo by Warren Gretz courtesy of US Department of Energy/National Renewable Energy Laboratory (DOE/NREL).
Now, if the ink is invisible and shows up only in invisible ultraviolet light, how come you can see it when you shine one of those special lights on it? If you've read our article on light, you'll know that atoms make light when they absorb energy, become unstable, and then emit (give out) the same energy a few moments later. What happens with security ink is that the atoms absorb ultraviolet light, become unstable, but then give out a slightly different, blueish light that our eyes can see. (This is like the process that happens in the white outer coating of a fluorescent lamp, which converts ultraviolet light made inside the tube into visible light that brightens up our homes.)
Marking property with security microdots
Of course, really savvy thieves could simply go out and buy an
ultraviolet light, wave it over the things they steal, find the
security markings and obliterate them. Is there anything science can
do about that? An Australian company called DataDot Technology has
come up with one possible solution. Instead of marking your property
with invisible ink, you spray it with thousands of invisible
"microdots" that store details of who your are. The dots are tiny
glue (adhesive) particles onto which a special identification number is etched
with a laser (and the details of who each number belongs to are
recorded on a computer database).
Each dot is about as big
as a grain of sand and has to be magnified at least 50 times before
it shows up. It's easy to cover every part of a car and its engine
with these magical markers, but it doesn't matter if thieves know
they're there; sometimes it even helps! One crime study in Australia
found that DataDots reduced car theft by over 60 percent; once thieves
know something is marked, they know it'll be harder to sell on and
they take their dodgy business elsewhere.
RFID tags
Opportunistic theft is a really big problem in stores, but technology can help to solve that problem too. As many retailers have discovered, all you have to do is fit a tiny RFID radio tag onto the merchandise you're selling and put a couple of detector gates in the doorway. If someone tries to steal something, the radio tag triggers an alarm as it passes through the gates. You can read more about this in our main article on RFID.
Photo: An RFID gate in a shop doorway. It works in two ways at once: you know the alarm will go off if you try to steal something so you think twice—it's a deterrent as well as an alarm.
