CONTEXT
Biometrics sensors for personal identification undergo a huge evolution since a few years, as it is not only reduced to governmental and enterprise markets anymore. Nowadays, fingerprint sensors can be found in consumer electronics such in smartphones and laptops. Basically, two main technologies can be mostly found in fingerprint sensors: one based on optical devices and another based on Silicon devices. The first one is a robust and mature technology which enables a high acquisition/ high resolution surface at a reasonable price, and allows to capture multiple fingerprints concurrently. However, prism-based optical sensors demonstrate some limitations: they are heavy, thick, bulky, non-conformable and raise concerns regarding integration, product design, portable uses and cost. On the other hand, Silicon devices, i.e. mostly capacitive, pressure or thermal devices, are used for consumer electronics, due to their small size and easiness for integration. However, when large sensing areas are required, it is not a possible solution for cost reasons.
CONCEPT & OBJECTIVES
PYCSEL will address the bottlenecks of current fingerprint identification systems using flexible electronics (also called ‘Thin and Organic Large Area Electronics’ (TOLAE)) technology. These thin conformable large-area sensors present the advantage:
- To be free of form factor constraints during integration;
- To show enhanced ergonomics in future innovative cost-efficient fingerprint identification systems while enabling large area/high resolution acquisition.
For this purpose, PYCSEL project will develop a low cost thin and large area fingerprint sensing surface enabling the personal identification via the development of a TOLAE technology, combining an organic sensor with a TFT matrix on a plastic foil. Based on the fact that personal recognition requires high resolution (500 dpi) and large (1 up to 4 fingers) sensors, the project focuses on the design, development and integration of a printed pyroelectric PVDF-based sensor layer on a IGZO TFT active matrix on foil and connected to an electronic driver and readout board, resulting in a thin fingerprint conformable sensor with no need for any optical bulky and/or costly extra components integration. Multiple fingerprints capture will be possible with the resulting large area hybrid system whose conformability allow easy further integration and ergonomic use especially for high growth and high value portable security uses.
Among other things, it will require developing a manufacturable process for a 500 ppi TFT backplane and a reliable fingerprint pyroelectric sensor, compliant with the 500 ppi high resolution requirements, including encapsulation (mechanical protection and shielding) and specific sensor poling methods. A specific demoboard will be also developed for each of the two formats of sensor (the first one is 256x256 pixels corresponding to a '1 finger' imager, and the second one is 1600x1500 pixels enabling a '4fingers' image capture).
The different steps of the PYCSEL project are depicted in the figure 1 below.
