Security is a top priority for digital mobile devices such as smartphones or laptops.
For this reason, many of these devices are no longer protected with a password from external access, but with a fingerprint scanner.
But even these can be tricked with some effort.
Researchers have now developed an ultrasound chip that captures a three-dimensional image of the fingertip.
This should be counterfeit-proof.
Who locks his smartphone or his laptop with the fingerprint, mostly imagines on the safe side.
The fingerprint of a human being is unique and unique as an identification feature.
As far as the fairy tale hour.
Even the printed photo of a fingerprint from a glass, enriched with some skin colored latex milk or white wood glue, is usually enough to deceive fingerprint scanners.
Just as hackers hacked the Hamburgian chaos computer club the Apple iPhone 5s , two days after the pompous market launch on September 20, 2013.
Ultrasonic image of the fingerprint including underlying tissue
Researchers led by David Horsley, Professor of Mechanical Engineering and Aeronautical Engineering at the Berkeley Sensor and Actuator Center at the University of Califórnia.
Berkeley and Davis, have now introduced a new filigree fingerprint scanner in the journal “Applied Physics Letters”.
Your scanner records an ultrasound image of the fingerprint, including the underlying tissue.
The recordings resemble those of ultrasound scans with which pregnant women are examined. The image is only substantially smaller, it is synonymous not an embryo, but a fingerprint.
“Echoes of elevations and valleys on the surface”
“The ultrasound images are recorded in the same way as in medical examinations,” explains Professor Horsley.
“Transducers on the chip emit a short ultrasonic pulse, and the converters receive echoes of elevations and valleys on the surface of the fingerprint.
” This recording technique produces far more than just one image of the finger. “Our ultrasonic fingerprint sensors can measure a three-dimensional, volumetric image of the finger surface and tissue under the surface,” emphasizes Horsley. “This makes fingerprint sensors more reliable and safer.”
Chip fits into a smartphone
The ultrasonic chip developed by Horsley’s team is small enough to fit into a smartphone.
The researchers placed tiny ultrasonic transducers on an area with an edge length of about one centimeter.
The distance between the transducers is 100 micrometers.
Each of these transducers emits ultrasonic waves that reflect the filigree groove surface.
Underneath the converters, there are transistors which can process the reflected ultrasound signals.
These data form the basis for a three-dimensional image of a fingerprint with a resolution of approximately 200 μm.
This resolution is sufficient to capture the skin structure with all its elevations in three dimensions.
Mass production process
The researchers are especially proud of the fact that they have succeeded in producing the fingerprint scanner in a mass-ready production process.
The so-called microelectromechanical systems (MEMS) already use smartphones in their tiny microphones, acceleration sensors and gyroscopes.
The researchers stacked several electrodes of silicon and molybdenum in layers one above the other.
In between, the scientists put a 800 nanometer (nm) thin layer of aluminum nitride.
This piezoelectric material generates ultrasound waves that reach a sound pressure of about 14 kilopascals.
Quick analyzes of material surfaces are also conceivable
David Horsley is convinced that this technology is suitable for low-cost mass production of ultrasound chips.
The researchers are now working closely with the company InvenSense in San José.
With these ultrasound chips, not only smartphones and laptops can be protected against illegal access in the future.
Also favorable and fast analyzes of material surfaces are conceivable with these chips.