Gregor Scheipl

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

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.

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.

Synthesis of a poly(2-azanorbornene) with a high degree of cis-TT-stereoregularity and a regular secondary solution structure

Methyl-N-(1-phenylethyl)-2-azabicyclo[2.2.1]hept-5-ene-3-carboxylate (AzaN) was synthesized as a diastereomerically pure monomer and subsequently polymerized with the ruthenium-based M31® catalyst. The poly(2-azanorbornene)s with polymerization degrees in the range from 100 to 300 exhibited high degrees of cis-TT stereoregularity in contrast to previously reported poly(2-azanorbornene)s that were prepared with molybdenum-based catalysts and exhibited cis-HT and trans-HT stereoregularity. The formation of regular secondary structures in acetonitrile solution was verified by circular dichroism and AFM measurements and supported by theoretical calculations of a polymer model with eight repeating units. Of special note are the large diameters of the secondary structures that are indicative of a multiple-strand filament.

Fully printable, flexible, large area organic optothermal sensors for human-machine-interfaces

Pyroelectric sensors presented in this work are based on polymers from the PVDF family which are comprised of a piezo- and/or pyroelectric polymer thin film capacitor, integrated with high performance organic thin film transistors operating at low voltages and acting as impedance converters, signal amplifiers and conditioners. For flexible integration with diverse electronic devices, large area processes applicable for industrial partners such as screen printing have been used for the fabrication of the sensors. With respect to the intended purpose for detection of human body radiation the absorbance of the impinging IR-light is dramatically increased by the application of printed carbon top electrodes, hence meeting the requirements for low-cost large area processability. Here we present good working integrated sensor devices based on two components, being an organic thin film transistor with a high-k-nanocomposite gate dielectric and a PVDF- copolymer based sensor. Besides, the integration of printed electrochemical transistors with printed sensors for large area applications has been realized successfully.

All printed touchless human-machine interface based on only five functional materials

We demonstrate the printing of a complex smart integrated system using only five functional inks: the fluoropolymer P(VDF:TrFE) (Poly(vinylidene fluoride trifluoroethylene) sensor ink, the conductive polymer PEDOT:PSS (poly(3,4 ethylenedioxythiophene):poly(styrene sulfonic acid) ink, a conductive carbon paste, a polymeric electrolyte and SU8 for separation. The result is a touchless human-machine interface, including piezo- and pyroelectric sensor pixels (sensitive to pressure changes and impinging infrared light), transistors for impedance matching and signal conditioning, and an electrochromic display. Applications may not only emerge in human-machine interfaces, but also in transient temperature or pressure sensing used in safety technology, in artificial skins and in disposable sensor labels.

Scanning pyroelectric microscopy for characterizing large-area printed ferroelectric sensors on the nanoscale

This work demonstrates a novel surface scanning method for the quantitative determination of the local pyroelectric coefficient in ferroelectric thin films. Such films find application in flexible and large-area printed ferroelectric sensors for gesture-controlled non-touch human-machine interface devices. The method is called Pyroelectric Scanning Probe Microscopy (PyroSPM)[1] and allows generating a map of the pyroelectric response with very high spatial resolution. In domains of previously aligned dipole moments small heat fluctuations are achieved by laser diode excitation from the bottom side thus inducing changes in the surface potential due to the pyroelectric effect. Simultaneously, the surface potential variations are detected by scanning surface potential microscopy thus forming the base for the pyroelectric coefficient map. The potential of the method is demonstrated on the basis of ferroelectric semi-crystalline copolymer thin films yielding local maxima of the pyroelectric coefficients around 40µC/m2K. Another promising feature of PyroSPM is the ability to visualize “screened” polarization thus enabling in-depth profiling of polarization distributions and domain formation and to study the composition dependence and the time and frequency behavior of ferroelectric nano-domains.

Performance and parameter variation of flexible organic thin film transistors in multicomponent organic sensors

Here we report on the fabrication and detailed characterization of flexible low-voltage organic thin-film transistors directly integrated with pyro- and piezoelectric sensors. The functional layer of the capacitive sensors is a ferroelectric fluoropolymer. The transistors on the other hand are based on a high-k nanocomposite gate dielectric and on pentacene as the organic semiconductor and can be operated well below 5V. It is shown, that the transistors can be fabricated on the fluororpolymer layer. Since the control of parameter spread is a very important topic in large area electronics, it was attempted to investigate the homogeneity of a significant set of devices by individual assessment of the layer composition and thickness, the pentacene morphology, the actual geometry and the electrical parameters. It turned out that starting from the measured device parameters such as layer thickness, capacitance, channel dimension, grain size and threshold voltage, the drain current can be calculated with high accuracy in a specified operation point. In addition, it is shown that the main influence on the parameter spread originates from the variations in the threshold voltage. Storage in air destroys the transistors on the long term, whereas bias stress measurements under inert conditions reveal that the interfaces are very stable.

Fabrication, characterization and modeling of PVDF based organic IR-sensors for human body recognition

Within this work a cost-effective thin film-sensor-technology based on PVDF-TrFE polymers for detection of ambient changes of temperature has been developed. A wet-\chemical fabrication routine for obtaining ferroelectric thin films has been developed leading to a gammabutyrolactone based sol-gel process. The suitability of the synthesized material with respect to its usage as IR-sensing layer has been evaluated by vibrational spectroscopy and various electrical characterizations. In a second step, the adaptation of the lab scale routines for large area printing techniques on flexible substrates and their influence on the overall sensor performance and stability has been developed and tested. For simplifying the design process of adequate sensors used in different industrial applications, a mathematical model based on the heat distribution in a multilayer sensor system has been assessed and revised by experiments.