Plastic fingerprint sensor also detects underlining veins

January 19, 2016 // By Julien Happich
FlexEnable and ISORG have jointly developed what they claim to be the world's first large area flexible fingerprint sensor on plastic designed for biometric applications.

With an active area of 86x86mm, a 84µm pitch (78µm pixel size with 6µm spacing) and a 1048576 pixel resolution (1024x1024), the flexible sensor is only 0.3mm thick and can operate in visible and near infra-red up to wavelengths of 900nm.

The technology is capable of measuring not only the fingerprint, but also the configuration of veins in the fingers, providing additional security versus that of a surface fingerprint alone.

This new sensor breakthrough has been achieved by deposition of organic printed photodetectors (OPD), pioneered by ISORG, onto a plastic organic thin-film transistor (OTFT) backplane, developed by FlexEnable, to create a flexible fingerprint sensor that is ultra-thin, light, robust and lensless.

The large label-thin sensing area can be applied to almost any surface – and even wrapped around the objects in our daily lives that we typically come into contact with – such as a car steering wheel that would recognize the driver as soon as the wheel is touched, or a credit card with integrated biometric detection that does not compromise current form factors. The addition of vein sensing on top of fingerprint sensing provides a second level of security, since each user’s vein pattern in the finger is unique and requires the user to be alive for detection to be successful.

Large area fingerprint sensors allow more information to be collected – which directly provides better performance on two key metrics compared to smaller sensor areas – higher security and lower false rejection rate. However, when using conventional silicon technology, large area fingerprint sensors become prohibitively expensive for many applications.

Flexible plastic fingerprint sensors bring cost advantages to large area manufacturing due to the low temperature and printing process that are used on plastic. Moreover, fingerprint sensors made of plastic have similar optical performances to conventional optical fingerprint sensors such as sensitivity, linearity, and low noise, but without the need for expensive and bulky optics.

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