Thin and flexible scanner reads fingerprints from nail to nail

TNO at Holst Centre, Solliance and TU/e worked together in the development of a thin and flexible scanner for fingerprints. Low-resolution image-sensor arrays have been demonstrated in the past, but the step toward high-resolution, high pixel-count image sensors suitable for commercial applications has been lacking to date. Gerwin Gelinck and Albert van Breemen took the flexible fingerprint scanner to the next level, and now have an article published on this subject in the current edition of Nature Electronics.


Efficient and cost-effectiveThe thin and flexible scanner is based on metal-halide perovskites. Perovskites are currently transforming the global solar panel market. They are as efficient as silicon, but are cost-effective and easy to produce on a large scale. Gerwin Gelinck, Chief Technology Officer TNO at Holst Centre, elaborates on the article in Nature Electronics: "Perovskites are marvelous materials! For the first time we show that these materials are also very good for light imaging and sensing applications. When combined with display-like transistors, we made a scanner that can capture high-resolution colour images as well as biometric fingerprinting".


Perovskite image sensor                         Perovskite image sensor stack


Metal-halide perovskites (MHPs) possess excellent opto-electronic properties, such as a broad light-absorption range and tuneable bandwidths, a high extinction coefficient, high charge-carrier mobility and long electron-hole diffusion lengths. As a result, the materials have been used as photo-active layers in solar cells, light-emitting diodes, lasers and photodetectors. They are also well-suited to low-cost, large-area solution processing, making them ideal candidates to replace commercial silicon semiconductors in photodetection applications such as image sensing, optical communication, environmental monitoring, and chemical or biological detection.


Nail-to-nail fingerprint scanningAlbert van Breemen, Senior Researcher TNO at Holst Centre who led the research, continues: "Because the imager is very thin, it can be wrapped around round objects. This is for instance advantageous in high-resolution, nail-to-nail biometric fingerprint scanning. Furthermore, we show that it can detect your heartbeat simultaneously, which is another safety feature. We believe that our perovskite image sensors are ideal for integration into everyday objects such as the backside of mobile phones and door handles as part of unobtrusive, secure-access control systems."


 High resolution fingerprint sensing         Scanning of color image (top: original, bottom: scanned image)


The adoption of this technology may be accelerated by tailoring the electro-optical properties of perovskites, as well as upscaling to larger active areas by using slot-die coating, for example. Light-sensing across both the visible and infrared spectrum could be enhanced, leading to improved applications in medical imaging, surveillance, and optical communication. Gerwin and Albert conclude: "We very much look forward to seeing where this technology will take us next."



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