All-Printed Touchless Human-Machine Interface

Project3PLAST - transfer lab-scale thin film processes to large-area printing processes

3PLAST - transfer lab-scale thin film processes to large-area printing processes

Acreo, Printed Electronics, was a partner of the European FP7 project 3PLAST (Pyroelectric and Piezoelectric Printable Large Area Sensor Technology), a collaboration with two Fraunhofer institutes (D), Joanneum Research (A), ASEM GmbH (D), Festo AG & Co. KG (D), IEE S.A. (Lu), Johannes Kepler Universität Linz (A), and Emfit Ltd (Fi).

Within 3PLAST polymer sensors integrated with organic electronics on large area flexible substrates are developed. The 3PLAST sensors will provide information on changes in temperature and pressure with a local resolution. The basic sensor device is comprised of a piezo- and/or pyroelectric polymer integrated with organic thin film transistors (OTFTs) or electrochemical transistors (ECTs) operating at low voltages acting as impedance converters and sensor signal amplifiers.

The figure to the right shows the concept for an integrated pyro- or piezoelectric sensor element. The sensor can be activated either by light from an IR laser diode, by human body radiation (finger, hand) or by pressure. One of the most relevant materials for the 3PLAST sensor technology is the PVDF-TrFE copolymer. PVDF copolymer solutions are developed and adjusted for printing processes. The sensitivity to human body radiation is shown by a waving finger over the sensor. The corresponding current output signal is shown in the figure below.

Low-cost manufacturing will be enabled by high-throughput processes such as screen- and reel-to-reel printing. Examples for envisioned applications of the integrated large area polymer sensor technology are smart skin, human machine interfaces, security systems (e.g. pedestrian protection in vehicles) and self-controlled machine monitoring.

Acreo's main mission in 3PLAST is to transfer lab-scale thin film processes to large-area printing processes adapted for production. Addressed printing techniques are: Screen-printing, ink-jet printing, bar coating, and R2R printing. The components printed are: PVDF-TrFE sensor elements, electrochemical transistors (ECTs) designed for the sensor elements and electrochemical display elements. Finally, these components will be integrated into an all printed application human machine interface (HMI) demonstrator sensor device. The figure to the right shows the layout of a sensor array for a touchless keypad.

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