Oxford University spin out company, Bodle Technologies believes phase-changing materials (PCMs) could be used in applications ranging from security and anti-counterfeiting to helping to control the temperature of a room, as well as in enabling low energy consuming electronic displays.

The PCMs used in Bodle’s applications is the same as those used in rewritable CDs and DVDs but, instead of using lasers to change the state of the material from amorphous to crystalline and vice versa, Bodle’s technology can be switched using optical, electrical and mechanical probing techniques.

“One thing we were asked by a number of people was if we could use the technology to save power in mobile devices,” said Dr Peiman Hosseini, Bodle’s co-founder and chief technology officer. Mobile devices and displays use LCDs or OLEDs to transmit images and require a powerful backlight to be viewed which is highly power intensive. “Our technology doesn’t require a backlight as it uses ambient light to reflect an image. It is similar to the way a Kindle works except that ours can create very deep, rich colours.”

A layer of PCM is sandwiched between two layers of a transparent electrode; these materials appear either transparent or ‘metallic-looking’. By placing the layers in a specific order, colourful films can be created by thin-film interference, controlled by a tuneable electric pulse. Changing the optical property of one layer changes the interference conditions that ultimately changes the colour of the whole stack.

“Unlike a backlit device, which is hard to see in bright sunlight, the images created by our device will look better the more ambient light hits the display,” Dr Hosseini claimed. “What’s more, the device only draws power when the image moves. For small mobile products, such as wearables, it would increase battery life by several times.”

Another use for the material is in the smart window market where it could be embedded into the glass and switched ‘on’ or ‘off’ to prevent infrared waves from entering a building or to confine them inside. This would either cool or warm the room without using air conditioning or heating, thereby saving energy and money.

The PCM technology could also be used to provide practically unbreakable security in future currencies, ID cards and official documents. “Next generation currency and passports will be made from plastic as it is cheaper to manufacture than paper,” Dr Hosseini explained. “We can apply a functional coating of our technology to a credit card or passport and have features that appear or disappear when it is excited by an electrical pulse or even mechanical pressure.”

Bodle expects to produce a prototype in each area by the end of 2016 and will focus on the most promising prospect to put into a pilot programme with its industry partners. Dr Hosseini predicted that a commercial product could be ready in three to four years.