Researchers from Holst Centre in Eindhoven and Imec in Leuven recently demonstrated a promising new technology: a high-tech foil that can scan finger and palm prints on a large surface. The new application, which is also inexpensive and supports high-resolution scans, has been made possible by thin-film technology.
How is it possible to scan finger and palm prints using only an extremely thin foil with a thickness of 0.1 millimetre? “We achieved it by integrating photodiodes and thin-film transistors in the foil,” explains Hylke Akkerman, program manager at Holst Centre, located on Eindhoven’s High Tech Campus. Holst Centre is a partnership between TNO and the research centre Imec, which started its life in Belgium.
Scanning fingerprints and registering heart rates
“The skin reflects light, and the sensors can use this reflected light to scan finger or palm prints,” continues Akkerman. “They also detect reflected light that has penetrated the top layers of the skin. This enables the sensors to register a heart rate and verify that the finger or palm print was made by a living person.”
“An X-ray detector made of synthetic foil can be folded, so a mobile system could fit in an ambulance, which would be ideal for responding to emergencies”
Police, customs and FBI
The finger and palm print scans are so detailed that they can be used by official bodies such as the police or customs. “Last spring, we gave a demonstration at the influential Society for Information Display (SID) symposium in Los Angeles, where we displayed a thin-film fingerprint scanner with a resolution of 500 ppi. This scanner even meets the high standards of the FBI.”
High-tech foil for smartphones
Holst Centre is currently engaged in talks with smartphone manufacturers, because the technology is ideal for use in smartphone screens. “Smartphone screens are getting bigger and bigger, and at the same time there is an increasing demand for phones with fingerprint identification,” explains Akkerman. “You can already use your fingerprint to log in or authorize payments. The sensor is often integrated in the home button, however, as smartphone bezels continue to shrink in size, home buttons are becoming obsolete. Our solution is a foil that makes the entire screen suitable for fingerprint identification.”
“Our thin-film fingerprint scanner with a resolution of 500 ppi meets the high standards of the FBI”
“Screen manufacturers currently already employ thin-film technology and the processes needed to apply these foils,” explains Akkerman. “So implementing this technology will not involve a major transition for them, while it will enable them to offer their customers smartphones with the entire screen as a fingerprint scanner. It will be affordable, too, so there is a good chance that this technology will soon be available in many smartphones.”
Mobile X-ray devices
The foil for scanning fingerprints is the most recent application of thin-film technology. “The technology can also be used for medical imaging,” continues Akkerman. “For example, ERs often use X-rays, but the current X-ray devices are heavy and fragile. We have developed a thin-film X-ray detector together with Philips Research. The properties of this detector have already reached the level that they now meet the stringent requirements for medical applications. The benefit of the foil is that thinner and lighter X-ray detectors can now be produced that will also be significantly more robust. Moreover, because an X-ray detector made of synthetic foil is flexible, you could fit a mobile system in an ambulance, which would be ideal for responding to emergencies.”
“We are also developing a way to use foils to scan aircraft wings for cracks and corrosion”
Scanning aircraft wings and foils for shoe soles
Holst Centre is also developing a way to use foils to scan aircraft wings for cracks and corrosion. Another application is in shoes with a foil integrated in the sole that measures pressure distribution during walking. “Applications like these require other thin-film technologies,” says Akkerman. “But these technologies will be available within a few years, too.”