Transparent Capacitive-Type Fingerprint Sensing Based on Zinc Oxide Thin-Film Transistors

A highly transparent, capacitive-type fingerprint-sensing panel is demonstrated using an active sensor matrix based on zinc oxide (ZnO) thin-film transistors (TFTs). In particular, the ZnO TFTs are used in each pixel not only as select switches but also for pre-amplification of signals. Compared to the select switch scheme, the pre-amplifier scheme shows significantly enhanced signals. It produces clear 50×50 size and 254 dpi fingerprint images, from which the minutia features are extracted. Furthermore, the sensor panel exhibits stable operations under the illumination of white light. This letter may open up potential applications of on-display transparent electronics that involve active circuits.