JOANNEUM RESEARCH MATERIALS PyzoFlex® Printed & Flexible Sensor
In organic and large-area printed electronics smart sensors for detection of physical forces are very promising with respect to novel user interface applications. Over the last decade, touch sensing devices have become more and more important. Multi-touch screens are now the de-facto standard in mobile devices such as phones and tablets, depth cameras are increasingly being used to capture gestural input in the living room and beyond. This rise in adoption of such ‘natural’ user interfaces shows there is a great deal of user demand for simpler ways of navigating information and content, where the computer interface is not a barrier, but enables them to accomplish tasks more quickly and easily. Application is for dynamic sensing of pressure/temperature changes as well as energy harvesting. Potential In various applications PyzoFlex® sensors are Printability, Cost Efficiency, Flexibility, Robustness and High dynamic detection an Energy Self-Sustaining a Spatial Resolution.
Key Facts: Sensor-Fabrication
- Low temperature fabrication on flexible/rigid substrates (≤ 100°C)
- Substrate sizes up to 420 x 420mm with a thickness ≤ 20mm.
- Semi-transparent sensors if solely PEDOT:PSS is used as electrode material.
- Cost efficient sheet to sheet manufacturing by industrial screen-printing process.
- Application specific sensor shapes based on CAD designed screen masks (max. resolution = 12000dpi)
- Feature sizes down to 100µm (depending on material and screen)
In Smart Surface, object means the transformation of a functionalized 2D-surface to a 3D-surface building the outer shell of an everyday object, thus leading to a functional extension. The pioneering approach of Smart Surface for realizing quickly reconfigurable objects is to integrate all functionalities on 2D flexible or even extensible (stretchable) substrates by scalable, cost efficient, industrial processes like printing, nanoimprinting, pick & place, and lamination and subsequently redefine these 2D functionalized substrates into the designed 3D shape e.g., by high pressure forming and injection molding for rigid objects. The functions include printed ultrathin multi-parameter sensors of various architectures for pressure, touch, strain, proximity and vital parameter monitoring, printed haptic feedback elements for intuitive interaction by pressure-sensitive touch with localized vibrotactile- and force-feedback, ultrathin light guiding films based on LEDs and advanced waveguides for uniform backlighting of input or decoration elements on 3D plastic surfaces and backlighting of curved leather, stone and wood structures. Thus, the object design requirements are combined from the very beginning with the specified functionality without the need for additional component assembly.
Like all piezoelectric materials, the PyzoFlex® polymer transducer develops an electrical charge proportional to a change in mechanical stress. The amplitude and frequency of the signal is directly proportional to the mechanical deformation of the material, resulting in a change in the surface charge density of the material so that a voltage appears between the electrode surfaces. When the force is reversed, the output voltage is of opposite polarity.
An alternating force therefore results in an alternating output voltage. PyzoFlex® is not suitable for static measurements as 
the electrical charges developed decay with a time constant that is determined by the dielectric constant and the internal resistance of the transducer, as well as the input impedance of the interface electronics to which the transducer is connected resulting in a minimal frequency measurable in the order of 0.001Hz. There are methods to achieve static measurement, but these require using PyzoFlex® as both an actuator and sensor, monitoring change in the actuation. The fundamental piezoelectric coefficients for charge or voltage predict, for small stress (or strain) levels, the charge density (charge per unit area) or voltage field (voltage per unit thickness) developed by the transducer. A properly designed interface circuit plays a key role in the optimization of PyzoFlex® transducers.
For more information Click https://www.joanneum.at/en/materials/research-areas/pyzoflexr or contact designhmi@gmail.com
