11.2 3D ultrasonic fingerprint sensor-on-a-chip

The increasing popularity of mobile devices such as smart phones in applications including smart payments and personal health sets a pressing need for improved security without compromised ease of use. Fingerprint recognition has emerged as a particularly attractive option. Unfortunately, present capacitive solutions suffer from poor accuracy in the presence of contamination such as perspiration, and in addition are easily compromised, e.g., with fingerprints recovered from the device surface.