When Apple unveiled fingerprint unlocking on its latest iPhone back in 2013, it heralded in a new age of biometrics-based consumer security.
But for the meticulously security conscious, the fingerprint scanning tech now featured by a variety of smartphones isn’t particularly secure.
Using an image-based scanning process, the technology can be spoofed using a picture of the appropriate fingerprint, making it fine for keeping dodgy selfies away from opportunistic prying eyes, but not much more than a gimmick if you’re serious about protecting sensitive data.
However, the solution looks to be here, in the form of a 3D fingerprint scanning chip.
using the same ultrasound technology used to image the bellies of pregnant women.
“Ultrasound images are collected in the same way that medical ultrasound is conducted,” said David A Horsley, professor of mechanical and aerospace engineering at the University of California, Davis.
“Transducers on the chip’s surface emit a pulse of ultrasound, and these same transducers receive echoes returning from the ridges and valleys of your fingerprint’s surface.”
The result is a technology that can’t be fooled by a picture, making it an appealing improvement for smartphones.
“Our ultrasonic fingerprint sensors have the ability to measure a three-dimensional, volumetric image of the finger surface and the tissues beneath the surface – making fingerprint sensors more robust and secure,” said Horsley.
And what’s more, the chip is made in a very similar way to existing smartphone components, making its adoption by major brands entirely viable.
The chip’s imager is made using microelectromechanical systems (MEMS) tech – already used in smartphones’ microphones, accelerometers and gyroscopes, and manufactured using a modified version of the process used to make those found in the iPhone.
“Our chip is fabricated from two wafers – a MEMS wafer that contains the ultrasound transducers and a CMOS [complementary metal-oxide-semiconductor] wafer that contains the signal processing circuitry,” explained Horsley.
“These wafers are bonded together, then the MEMS wafer is ‘thinned’ to expose the ultrasound transducers.”
As a result, the technology, the details of which are published today in the journal Applied Physics Letters, can be made cheaply at high volume – a must if it is to find its way into the next generation of smartphones.
“Because we were able to use low-cost, high-volume manufacturing processes that produce hundreds of millions of MEMS sensors for consumer electronics each year, our ultrasound chips can be manufactured at an extremely low cost,” said Horsley.
But the technology isn’t just destined for smartphones. As it has just a 1.8V power supply and low energy requirements, its makers believe it could bring ultrasound to a host of other miniaturised applications.
“Our ultrasound transducers have high sensitivity and the receiver electronics are located directly beneath the array, which results in low electrical parasitics,” he said.
“Using low-voltage integrated circuits will reduce the cost of our sensor and open up myriad new applications where the cost, size, and power consumption of existing ultrasound sensors are currently prohibitive.”