Newer iPhone models feature a fingerprint sensor for security — and a high-quality camera capable of taking a photo that can fool that fingerprint sensor. It's not an issue if you're mostly interested in feeling futuristic, but engineers have come up with a better solution for those more concerned about security.

The new fingerprint sensor, described in the journal Applied Physics Letters, contains a tiny ultrasound imager. This allows the sensor not only to capture more details about the distinctive designs on the surface of your fingertips, but also to collect information about tissues below the surface. 

"Existing smartphones use capacitive fingerprint sensors that measure a 2D image of the finger surface," said senior study author David Horsley of the University of California, Davis to Tech Times. "The ultrasound image may allow discriminating between a live finger and a printed fingerprint — a vulnerability of capacitive sensors."

Ultrasound imaging works by bouncing ultrasound pixels off of a certain body part — in this case, the tip of a finger. The way in which these pixels get reflected back to the sensor allows it to construct an accurate 3D image of not only the surface of the skin, but also the tissue beneath it.

"In particular, the dermis layer beneath the epidermis possesses the same fingerprint image as the epidermis – or surface skin – and can be used to recognize a user even if the skin is very wet, very dry, oily or dirty," Horsley explained.

More work is still needed to realize some of the 3D imaging capability, he noted. The new sensor will also need to be industrialized so that it can actually be packaged within a phone. As for when the technology might start being incorporated in consumer electronics, Horsely said his "best guess is one to two years."

Right now, the ultrasonic sensors are nearly twice as expensive to produce as the capacitative sensors currently found in smartphones. Nevertheless, Horsely said that he and his team "have ideas that will allow us to reduce the cost further."

If people are willing to pay for a fingerprint sensor that can be tricked by a simple printed photo, it seems reasonable to pay a little more for a security system that can't be penetrated using common household items.

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