Happy International Veterinary Medicine Day! My best friend is a vet, and she spends her days looking after our pets. One of the things she does is inject microchips, to help us identify and find lost pets.

In Australia today, most dogs and cats carry a tiny microchip – about the size of a grain of rice – under the skin between their shoulder blades. Your pet can’t feel its chip, but this mini device helps many furry friends to find their way home.

Lost and found: family pet

Vets like my friend use a special needle to inject a microchip under your pet’s skin. This is quick and only stings for a second, much like a vaccination. Once injected, the chip stays with your pet for life.

Each chip is coded with a 15-digit identification (ID) number. This number is listed in a database, matched with your pet’s name, address and owner details.

Your pet’s microchip is passive, which means for the most part, it does nothing.

“Basically it’s a glass tube with a copper coil inside it. It has no battery or anything like that,” says Bruce Knight, of Micro Products Australia.

But if you lose your pet, or find a lost pet, a vet can scan its microchip to reveal its ID number.

“Just like scanning groceries at the supermarket,” says Bruce.

Radio frequency identification: Power up!

To communicate your pet’s ID number, the chip needs a source of energy. Providing this energy is the job of a microchip scanner.

Microchip scanners broadcast a low frequency radio wave of 135 kHz, or 135,000 vibrations per second. This wave is invisible, a very slow version of the same radio waves you tune into when you listen to music on the radio.

“All pet microchips must operate on that frequency,” says Bruce. “No matter where you go in the world, they will have a scanner that can read your microchip.”

When this low frequency radio wave bumps into your pet’s microchip, it sends a tiny electrical current whirling around the chip’s copper coil. Like a key winds a clock, the current provides just enough energy to power the microchip.

Once powered, the microchip can emit its own unique radio wave. The scanner captures this radio wave and decodes it, displaying your pet’s ID on its screen. The scanner must be held close to the microchip, because the radio wave has so little energy.

This use of radio waves to send coded information through the air is called radio frequency identification (RFID).

Did you know? Some microchips include a thermometer: when you scan the chip, it sends back your pet’s temperature as well as their ID.

From libraries to polar bears

RFID chips are everywhere: they’re used by libraries to manage books, shops to prevent shoplifting, and farmers to track the farm their animals grew up on, and the vaccinations they’ve had. Researchers use RFID chips to track rhinos in Namibia and polar bears in the Arctic.

You’ll also find RFID used in automatic toll booths, car immobilisers, electronic passports, smart travel cards and contactless card payments.

I originally wrote this article for CSIRO’s Double Helix magazine. Happy International Veterinary Medicine Day!