Dresden 2006 – scientific programme

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DF: Dielektrische Festkörper

DF 4: Internal Symposium “Ferroelectric Materials for Smart Structures”

DF 4.2: Talk

Tuesday, March 28, 2006, 10:10–10:30, K{\"O}N Farb

Using ferro-electrical material for biometrical application — •Rainer Schmitt — 86 Ironwood Way, Palm Beach Gardens, FL 33418, USA

The matrix structure of 1-3 piezo composite consisting ferro-electrical pzt-pillars, spaced 120 microns apart in a polymer matrix has successfully been utilized for fingerprinting. For this application the pillars are driven in serial resonance mode exhibiting a different electrical impedance when exposed to the very different acoustic load of a finger tip structure, which is 1.5 Mrayls for a ridge and only 350 rayls for a valley. Individual pillars are addressed by a cross-hatched electrode structure on the top and the bottom of the sensor. Under typical material choices (pzt, polymer, electrodes and low acoustical impedance substrate as well as pillar pitches ranging from 50 - 150 microns the variation in the electrical pillar impedances is approx. 1: 4 for the ridge and valley, providing sufficient discrimination for fingerprinting. Since the sensor can be produced inexpensively using soft mold technology, developed by Fraunhofer IKTS large scale application for cell phone, car, computer access are expected. This principle of acoustical impediography, verified at a resolution of 250 dpi is now being expanded to a resolution of 500 dpi by developing the appropriate 1-3 composite with a pillar pitch of 50 microns.