Markus Krause

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.

Pyroelectric, piezoelectric, and photoeffects in hydroxyapatite thin films on silicon

Tofail et al.3 have found that the dipole of HA is the hydroxyl (OH) ion, which lies along the crystallographic c-axis within the tunnel formed by phosphate (PO4) tetrahedra. In adjacent tunnels, the OH ions could point in a parallel direction or in an anti-parallel one. We believe that the high-temperature calcination crystallized the HA film on silicon and converted most of the OH pairs to a parallel configuration. Thus the HA developed a domain structure with randomly oriented dipoles. Upon cooling, sufficient domains reoriented in polarity so as to result in a net polar structure. This is due to the crystalline character of the silicon substrate and texturing. The photocurrent is caused by the silicon alone.

Optimized pyroelectric properties of 0-3 composites of PZT particles in polyurethane doped with lithium perchlorate

A substantial improvement in the performance of pyroelectric 0-3 composites of ceramic particles in a polymer matrix has been achieved by doping the polymer matrix material. Readily prepared and polarized films with various volume fractions of lead zirconate-titanate (PZT) particles in polyurethane have been doped in a solution of lithium perchlorate in acetone to increase the conductivity. With an appropriate conductivity, the dielectric permittivities of the ceramic particles and the polymer matrix become matched, resulting in an improvement of the pyroelectric coefficient from about 6 muC/(m2K) to about 50 muC/(m2K). The experimental results are explained by theoretical predictions.

Pyroelectric, piezoelectric and photoeffects in hydroxyapatite thin films on silicon

Tofail et al.3 have found that the dipole of HA is the hydroxyl (OH) ion, which lies along the crystallographic c-axis within the tunnel formed by phosphate (PO 4 ) tetrahedra. In adjacent tunnels, the OH ions could point in a parallel direction or in an anti-parallel one. We believe that the high-temperature calcination crystallized the HA film on silicon and converted most of the OH pairs to a parallel configuration. Thus the HA developed a domain structure with randomly oriented dipoles. Upon cooling, sufficient domains reoriented in polarity so as to result in a net polar structure. This is due to the crystalline character of the silicon substrate and texturing. The photocurrent is caused by the silicon alone.

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.

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.

Large area piezoelectric impact sensors

Printed electronics is an active area of research which enables production of electrical devices on various substrates. The use of highly insulating materials and the employment of dielectric phenomena based on the piezo- and pyroelectric effect in polar insulators promise large area sensors useful in protection sensor systems to save pedestrians. In this paper we propose a car safety system based on printed piezo- and pyroelectric sensors. Their use in pedestrian saving systems is exemplified by a toy-car-demonstrator. The sensors are based on ferroelectric polymers, printed on flexible PET substrates. The piezoelectric coefficients of the printed ferroelectric polymer film are typically 25 pC/N, sufficient for impact detection in car crash situations. The sensor speed is very fast, enabling efficient protection mechanisms to safe the life of pedestrians. The simple and potentially low cost fabrication is advantageous in comparison to systems currently available on the market.

PbTiO 3 /P(VDF-TrFE) nanocomposites for flexible skin

Large area electronics is mainly driven by the display industry [1]. Advanced technology schemes, like electronic skin for flexible, full body tactile sensors in robotics etc. have emerged recently [2]. In general, large area electronic surfaces consist of a backplane including transistor matrices and a frontplane, giving functionality to the electronic surface. Frontplanes may benefit from functional electrets in memories [3] and in sensors for monitoring changes in ambient pressure or temperature [4, 5].