Ultra-high Resolution Pressure Sensing Uses Matrices of Vertical Piezoelectric Nanowire

To Reconstruct the Smallest Features of Human Fingerprints

The project's proof of concept demonstrates that a matrix of interconnected piezoelectric zinc-oxide (ZnO) nanowires grown on silicon can reconstruct the smallest features of human fingerprints at 1,000 dots per inch (DPI).

"The pressure-based fingerprint sensor derived from the integration of piezo-electric ZnO nanowires grown on silicon opens the path to ultra-high resolution fingerprint sensors, which will be able to reach resolution much higher than 1,000 DPI," said Antoine Viana, Leti's project manager. "This technology holds promise for significant improvement in both security and identification applications."

The eight-member project team of European companies, universities and research institutes fabricated a demonstrator embedding a silicon chip with 250 pixels, and its associated electronics for signal collection and post-processing. The chip was designed to demonstrate the concept and the major technological achievements, not the maximum potential nanowire integration density. Long-term development will pursue full electronics integration for optimal sensor resolution.

The project also provided valuable experience and know-how in several key areas, such as optimization of seed-layer processing, localized growth of well-oriented ZnO nanowires on silicon substrates, mathematical modeling of complex charge generation, and synthesis of new polymers for encapsulation. The research and deliverables of the project have been presented in scientific journals and at conferences, including Eurosensors 2016 in Budapest.

The 44-month, €2.9 million PiezoMAT (PIEZOelectric nanowire MATrices) research project was funded by the European Commission in the Seventh Framework Program. Its partners include:

• Leti (Grenoble, France): A leading European center in the field of microelectronics, microtechnology and nanotechnology R&D, Leti is one of the three institutes of the Technological Research Division at CEA, the French Alternative Energies and Atomic Energy Commission. Leti's activities span basic and applied research up to pilot industrial lines. www.leti-cea.com/cea-tech/leti/english

• Fraunhofer IAF (Freiburg, Germany): Fraunhofer IAF, one of the leading research facilities worldwide in the field of III-V semiconductors, develops electronic and optical devices based on modern micro- and nanostructures. Fraunhofer IAF's technologies find applications in areas such as security, energy, communication, health, and mobility. www.iaf.fraunhofer.de/en

• Centre for Energy Research, Hungarian Academy of Sciences (Budapest, Hungary):  The Institute for Technical Physics and Materials Science, one of the institutes of the Research Centre, conducts interdisciplinary research on complex functional materials and nanometer-scale structures, exploration of physical, chemical, and biological principles, and their exploitation in integrated micro- and nanosystems www.mems.hu, www.energia.mta.hu/en

• Universität Leipzig (Leipzig, Germany): Germany's second-oldest university with continuous teaching, established in 1409, hosts about 30,000 students in liberal arts, medicine and natural sciences. One of its scientific profiles is "Complex Matter", and contributions to PIEZOMAT are in the field of nanostructures and wide gap materials. www.zv.uni-leipzig.de/en/

• Kaunas University of Technology (Kaunas, Lithuania): One of the largest technical universities in the Baltic States, focusing its R&D activities on novel materials, smart devices, advanced measurement techniques and micro/nano-technologies. The Institute of Mechatronics specializes on multi-physics simulation and dynamic characterization of macro/micro-scale transducers with well-established expertise in the field of piezoelectric devices. http://en.ktu.lt/

• SPECIFIC POLYMERS (Castries, France): SME with twelve employees and an annual turnover of about 1M€, SPECIFIC POLYMERS acts as an R&D service provider and scale-up producer in the field of functional polymers with high specificity (>1000 polymers in catalogue; >500 customers; >50 countries). www.specificpolymers.fr/

• Tyndall National Institute (Cork, Ireland): Tyndall National Institute is one of Europe's leading research centres in Information and Communications Technology (ICT) research and development and the largest facility of its type in Ireland. The Institute employs over 460 researchers, engineers and support staff, with a full-time graduate cohort of 135 students. With a network of 200 industry partners and customers worldwide, Tyndall generates around €30M income each year, 85% from competitively won contracts nationally and internationally. Tyndall is a globally leading Institute in its four core research areas of Photonics, Microsystems, Micro/Nanoelectronics and Theory, Modeling and Design. www.tyndall.ie/

• OT-Morpho (Paris, France): OT-Morpho is a world leader in digital security & identification technologies with the ambition to empower citizens and consumers alike to interact, pay, connect, commute, travel and even vote in ways that are now possible in a connected world. As our physical and digital, civil and commercial lifestyles converge, OT-Morpho stands precisely at that crossroads to leverage the best in security and identity technologies and offer customized solutions to a wide range of international clients from key industries, including Financial services, Telecom, Identity, Security and IoT. With close to €3bn in revenues and more than 14,000 employees, OT-Morpho is the result of the merger between OT (Oberthur Technologies) and Safran Identity & Security (Morpho) completed in 31 May 2017. Temporarily designated by the name "OT-Morpho", the new company will unveil its new name in September 2017. For more information, visit www.morpho.com and www.oberthur.com