Martin Zirkl

An All‐Printed Ferroelectric Active Matrix Sensor Network Based on Only Five Functional Materials Forming a Touchless Control Interface

An All-Printed Ferroelectric Active Matrix Sensor Network Based on Only Five Functional Materials Forming a Touchless Control Interface

Flexible active-matrix cells with selectively poled bifunctional polymer-ceramic nanocomposite for pressure and temperature sensing skin

A monolithically integrated bifunctional frontplane is introduced to large area electronics. The bifunctional frontplane element is based on a composite foil of piezoelectric ceramic lead titanate nanoparticles embedded in a ferroelectric poly(vinylidene fluoride trifluoroethylene) polymer matrix. Bifunctionality to pressure and temperature changes is achieved by a sequential, area selective two-step poling process, where the polarization directions in the nanoparticles and the ferroelectric polymer are adjusted independently. Thereby, sensor elements that are only piezoelectric or only pyroelectric are achieved. The frontplane foil is overlaid on a thin-film transistor backplane. Our work constitutes a step toward multifunctional frontplanes for large area electronic surfaces.

High-mobility pentacene organic field-effect transistors with a high-dielectric-constant fluorinated polymer film gate dielectric

High-performance pentacene organic thin-film transistors with double layers of the terpolymer electret poly(vinylidene fluoride/tetrafluoroethylene/hexafluoropropylene) and the polymer poly(vinyl cinnamate) as a gate dielectric are reported. The electret is a high-k dielectric polymer with a static dielectric constant of e=14. The transistors show an intrinsic field-effect mobility in the range of μi=1cm2∕Vs and an on- to off-current ratio of about 105. High-k polymer gate dielectrics seem promising for organic nonvolatile memory and sensor field-effect transistors.

FlexSense: a transparent self-sensing deformable surface

We present FlexSense, a new thin-film, transparent sensing surface based on printed piezoelectric sensors, which can reconstruct complex deformations without the need for any external sensing, such as cameras. FlexSense provides a fully self-contained setup which improves mobility and is not affected from occlusions. Using only a sparse set of sensors, printed on the periphery of the surface substrate, we devise two new algorithms to fully reconstruct the complex deformations of the sheet, using only these sparse sensor measurements. An evaluation shows that both proposed algorithms are capable of reconstructing complex deformations accurately. We demonstrate how FlexSense can be used for a variety of 2.5D interactions, including as a transparent cover for tablets where bending can be performed alongside touch to enable magic lens style effects, layered input, and mode switching, as well as the ability to use our device as a high degree-of-freedom input controller for gaming and beyond.

PyzoFlex: printed piezoelectric pressure sensing foil

Ferroelectric material supports both pyro- and piezoelectric effects that can be used for sensing pressures on large, bended surfaces. We present PyzoFlex, a pressure-sensing input device that is based on a ferroelectric material. It is constructed with a sandwich structure of four layers that can be printed easily on any material. We use this material in combination with a high-resolution Anoto-sensing foil to support both hand and pen input tracking. The foil is bendable, energy-efficient, and it can be produced in a printing process. Even a hovering mode is feasible due to its pyroelectric effect. In this paper, we introduce this novel input technology and discuss its benefits and limitations.

Synthesis of Ferroelectric Poly(Vinylidene Fluoride) Copolymer Films and their Application in Integrated Full Organic Pyroelectric Sensors

A sol-gel-based fabrication route for obtaining ferroelectric P(VDF-TrFE) thin films via a spin-coating technique at low temperatures was developed. The ferroelectric and pyroelectric properties of IR-sensors based on these layers were determined by hysteresis loop measurements, by dielectric characterization and by the laser intensity modulation method. On-chip stepwise poling at room temperature turned out to be very effective in increasing the pyroelectric current response. Finally, the sensors were directly integrated with organic thin film transistors to guarantee a low impedance read-out of the response.

Transparent pyroelectric sensors and organic field-effect transistors with fluorinated polymers: steps towards organic infrared detectors

Polymer electrets from the polyvinylidene family are highly suitable materials for plastic electronics. The high dielectric constant of such polymers in both the ferro- and non-ferroelectric phase is most suitably employed in gate dielectrics in organic field-effect transistors. The pyro- and piezoelectric response makes ferroelectric polymer electrets also an ideal choice for organic temperature, infrared radiation and pressure sensors. Here we report steps towards transparent organic pyroelectric infrared sensors: The infrared sensor element is based on poly (vinylidene fluoride), the top contact pentacene transistor on poly(vinylidene-fluoride tetrafluoroethylene hexafluoropropylene) and poly(vinyl cinnamate) as gate dielectric. Steps for combining the ferroelectric polymer sensors and transistors to a fully organic temperature and infrared sensing element are outlined. The sensor concept may be easily scaled up to the production of sensor arrays for thermal imaging

FlexCase: Enhancing Mobile Interaction with a Flexible Sensing and Display Cover

FlexCase is a novel flip cover for smartphones, which brings flexible input and output capabilities to existing mobile phones. It combines an e-paper display with a pressure- and bend-sensitive input sensor to augment the capabilities of a phone. Due to the form factor, FlexCase can be easily transformed into several different configurations, each with different interaction possibilities. Users can use FlexCase to perform a variety of touch, pressure, grip and bend gestures in a natural manner, much like interacting with a sheet of paper. The secondary e-paper display can act as a mechanism for providing user feedback and persisting content from the main display. In this paper, we explore the rich design space of FlexCase and present a number of different interaction techniques. Beyond, we highlight how touch and flex sensing can be combined to support a novel type of gestures, which we call Grip & Bend gestures. We also describe the underlying technology and gesture sensing algorithms. Numerous applications apply the interaction techniques in convincing real-world examples, including enhanced e-paper reading and interaction, a new copy and paste metaphor, high degree of freedom 3D and 2D manipulation, and the ability to transfer content and support input between displays in a natural and flexible manner.

PyzoFlex: a printed piezoelectric pressure sensing foil for human machine interfaces

Ferroelectric material supports both pyro- and piezoelectric effects that can be used for sensing pressures on large, bended surfaces. We present PyzoFlex, a pressure-sensing input device that is based on a ferroelectric material (PVDF:TrFE). It is constructed by a sandwich structure of four layers that can easily be printed on any substrate. The PyzoFlex foil is sensitive to pressure- and temperature changes, bendable, energy-efficient, and it can easily be produced by a screen-printing routine. Even a hovering input-mode is feasible due to its pyroelectric effect. In this paper, we introduce this novel, fully printed input technology and discuss its benefits and limitations.

PbTiO3 – P(VDF-TrFE) – Nanocomposites for Pressure and Temperature Sensitive Skin

Nanocomposites of a ferroelectric matrix polymer with dispersed ferroelectric ceramic nanoparticles can be polarized to be piezo- or pyroelectric alone at a given temperature, due to the different origin of piezoelectricity in polymers (dipole density) and ceramics (intrinsic). With a two-step poling procedure, which allows selective poling of the ceramic inclusion and the ferroelectric polymer, bifunctionality is achieved in the same material. The selective poling of filler and matrix phase is proved by ferroelectric hysteresis measurements at room temperature. Such bifunctional materials may be interesting for artificial skin, sensitive to changes in pressure and temperature.