Ultrasound provides better fingerprint scanner

Nature : Most electronic fingerprint scanners identify prints by generating a current where the fingers’ ridges touch the scanner and mapping their pattern. The scanners are susceptible to failure, however, due to moisture and dirt, which can prevent them from detecting the ridges and the valleys in between. Now David Horsley of the University of California, Davis, and his colleagues have developed an alternative scanner that uses ultrasound. The scanner employs a chip covered in aluminum nitride, which can convert mechanical stress to electrical signals. When a finger is pressed against the device, an ultrasound pulse is generated that reflects back from the finger with a pattern dependent on its ridges and valleys. With a longer pulse, the scanner can even measure the depth of the valleys, which can help identify fake fingerprints. Horsley’s team says that the use of aluminum nitride—already used in chip manufacturing—may overcome some of the difficulties of incorporating ultrasound devices into commercial electronics.