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Toy-Brick Tensile Tester

Radial Stretching System

SoMaP präsentiert einen auf Spielzeugbausteinen basierenden Tisch-Tensometer für Forschung und Lehre ...  mehr zu Toy-Brick Tensile Tester (Titel)

Radial Stretching System

Radial Stretching System

SoMaP präsentiert ein Open Source Projekt für Soft Matter Research ...  mehr zu Radial Stretching System (Titel)

ERC Grant 2012

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Wir befinden uns im 10.Stock des TNF-Turms ...  mehr zu Camplusplan (Titel)

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Research Highlights

April 2016 - Cover Advanced Science

From Playroom to Lab: Tough Stretchable Electronics Analyzed with a Tabletop Tensile Tester Made from Toy-Bricks

Toy bricks are an ideal platform for the cost-effective rapid prototyping of a tabletop tensile tester with measurement accuracy on par with expensive, commercially available laboratory equipment. Here, a tester is presented that is not only a versatile demonstration device in mechanics, electronics, and physics education and an eye-catcher on exhibitions, but also a powerful tool for stretchable electronics research. Following the “open-source movement” the build-up of the tester is described and all the details for easy reproduction are disclosed. A a new design of highly conformable all-elastomer based graded rigid island printed circuit boards is developed. Tough bonded to this elastomer substrate are imperceptible electronic foils bearing conductors and off-the-shelf microelectronics, paving the way for next generation smart electronic appliances.



Oktober 2015 - Cover Nature Materials

Flexible high power-per-weight perovskite solar cells with chromium oxide–metal contacts for improved stability in air

Photovoltaic technology requires light-absorbing materials that are highly efficient, lightweight, low cost and stable during operation. Organolead halide perovskites constitute a highly promising class of materials, but suffer limited stability under ambient conditions without heavy and costly encapsulation. Here, we report ultrathin (3 μm), highly flexible perovskite solar cells with stabilized 12% efficiency and a power-per-weight as high as 23 W g−1. To facilitate air-stable operation, we introduce a chromium oxide–chromium interlayer that effectively protects the metal top contacts from reactions with the perovskite. The use of a transparent polymer electrode treated with dimethylsulphoxide as the bottom layer allows the deposition—from solution at low temperature—of pinhole-free perovskite films at high yield on arbitrary substrates, including thin plastic foils. These ultra-lightweight solar cells are successfully used to power aviation models. Potential future applications include unmanned aerial vehicles—from airplanes to quadcopters and weather balloons—for environmental and industrial monitoring, rescue and emergency response, and tactical security applications.



Jänner 2015 - Cover Advanced Materials

An Imperceptible Plastic Electronic Wrap

Extremely compliant sub-2-μm sensor films enable temperature mapping on complex 3D objects, like integrated circuits on printed circuit boards, food packages, and on human skin. In their stretchable form, these metal films withstand strains up to 275%. This imperceptible electronic foil technology platform offers new avenues for the design of complex, hybrid rigid-island stretchable-interconnect electronic devices such as RGB light-emitting diode (LED) strips that can be stretched and twisted without impairing their function.



Juni 2013 - Front Cover Green Chemistry

Natural resin shellac as a substrate and a dielectric layer for organic field-effect transistors

Biocompatible and sustainable electronic-grade materials are integral for the development of electronics for biointegration and ‘use-and-throw’ applications. Herein we report the use of the natural resin shellac in organic field-effect transistors. Shellac was employed to cast robust and smooth substrates suitable for durable transistor devices. In addition shellac displays excellent insulating properties enabling its use as a high-quality dielectric layer for organic field-effect transistor (OFET) devices. We demonstrate that two common organic semiconductors, pentacene and C60, show hysteresis-free operation in OFETs that employ shellac both as the substrate and as dielectric material. Shellac is a fully biocompatible (even edible) material that offers many advantages for OFET fabrication, including high dielectric breakdown fields, simple solution processing from ethanol solutions, and low temperature crosslinking at 50–70 °C. This work shows that shellac as a biomaterial can enable OFET applications where biocompatibility is necessary.



Mai 2013 - Inside Front Cover Journal of Materials Chemistry A

Intrinsically stretchable and rechargeable batteries for self-powered stretchable electronics

Stretchable electronic circuits conform to irregular three dimensional surfaces. They are formed with soft materials and contain electronic circuits, sensors, and other components. We report on a soft matter based rechargeable electrochemical power storage element for such devices. The chemistry is based on a rechargeable alkaline manganese battery concept. The cells withstand more than 700 mechanical stretch relaxation cycles up to 25% strain, with an average cell capacity of 6.5 mA h. Combined with wireless power transmission or stretchable solar cells, the rechargeable battery can be used to store and supply energy in stretchable electronic devices.



März 2013 - Front Cover Advanced Materials

Hydrogen-Bonded Semiconducting Pigments for Air-Stable Field-Effect Transistors

Extensive intramolecular π-conjugation is considered to be requisite in the design of organic semiconductors. Here, two inkjet pigments, epindolidione and quinacridone, that break this design rule are explored. These molecules afford intermolecular π-stacking reinforced by hydrogen-bonding bridges. Air-stable organic field effect transistors are reported that support mobilities up to 1.5 cm2/Vs with T80 lifetimes comparable with the most stable reported organic semiconducting materials.



May 2012 - Back Cover Physica Status Solidi (a)

Intrinsically stretchable and rechargeable batteries for self-powered stretchable electronics

Ultrapure aluminium was thermally evaporated onto various plastics (polyethylene 2.6-naphthalate, PEN; polyethylene terephthalate, PET; polyimide, PI and glass for comparison) and potentiostatically anodized in a citric buffer. The anodisation procedure was monitored coulometrically and each alumina film formed was characterized by impedance spectroscopy. The resulting anodic alumina films were amorphous (proven by X-ray diffraction, XRD) and acted as dielectric material in a solid state capacitor with Au top electrode. The capacitors characteristics were evaluated using IV curves and frequency domain measurements. The performance of the capacitors demonstrated low leakage currents and low dielectric losses. The contrary properties capacity and breakdown voltage could be chosen by selecting the anodisation voltage. For each substrate apparent oxide formation factors and capacities were determined coulometrically. The ratio between apparent formation factor and projected area allowed determining the surface roughness. This surface roughness together with the high purity aluminium films and the anodisation compression was responsible for the unexpected high mechanical stability of this composite material.



März 2012 - Cover MRS Bulletin

Materials for stretchable electronics

Electronics can be made on elastically stretchable “skin.” Such skins conform to irregularly curved surfaces and carry arrays of thin-film devices and integrated circuits. Laypeople and scientists intuitively grasp the concept of electronic skins; material scientists then ask “what materials are used?” and “how does it work?” Stretchable circuits are made of diverse materials that span more than 12 orders of magnitude in elastic modulus. We begin with a brief overview of the materials and the architecture of stretchable electronics, then we discuss stretchable substrates, encapsulation, interconnects, and the fabrication of devices and circuits. These components and techniques provide the tools for creating new concepts in biocompatible circuits that conform to and stretch with living tissue. They enable wireless energy transfer via stretchable antennas, stretchable solar cells that convert sunlight to electricity, supercapacitors, and batteries that store energy in stretchable electronic devices. We conclude with a brief outlook on the technical challenges for this revolutionary technology on its road to functional stretchable electronic systems.



Jänner 2012 -Front Cover Advanced Materials

Indigo - A Natural Pigment for High Performance Ambipolar Organic Field Effect Transistors and Circuits

Millenniums-old natural dye indigo - a “new” ambipolar organic semiconductor. Indigo shows balanced electron and hole mobilities of 1 × 10−2 cm2 V−1 s−1 and good stability against degradation in air. Inverters with gains of 105 in the first and 110 in the third quadrant are demonstrated. Fabricated entirely from natural and biodegradable compounds, these devices show the large potential of such materials for green organic electronics.



Jänner 2012 - Front Cover Soft Matter

Harnessing snap-through instability in soft dielectrics to achieve giant voltage-triggered deformation

A soft dielectric membrane is prone to snap-through instability. We present theory and experiment to show that the instability can be harnessed to achieve giant voltage-triggered deformation. We mount a membrane on a chamber of a suitable volume, pressurize the membrane into a state near the verge of the instability, and apply a voltage to trigger the snap without causing electrical breakdown. For an acrylic membrane we demonstrate voltage-triggered expansion of area by 1692%, far beyond the largest value reported in the literature. The large expansion can even be retained after the voltage is switched off.



Mai 2011 - Front Cover Advanced Materials

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

Macroelectronic components combining different classes of devices often suffer from the high complexity and costs of the manufacturing processes. The printing of an active-matrix sensor network using only five functional inks is demonstrated. The result is an all-printed monolithically integrated touchless input interface, including ferroelectric sensor pixels, organic transistors for impedance matching, and an electrochromic display.



Februar 2011 - Inside Front Cover Journal of Materials Chemistry

Exotic materials for bio-organic electronics

“Exotic” materials have become the focus of recent developments in organic electronics that envision biocompatibility, biodegradability, and sustainability for low-cost, large-volume electronic components. In this brief review, we discuss firstly the use of paper, leather, silk, hard gelatine, and bio-degradable plastics as substrates for electronic devices, and secondly smoothing agents, such as polydimethylsiloxane and aurin. Thirdly, we describe DNA and nucleobases as examples of exotic dielectrics with low dielectric losses and leakage currents as well as sufficiently high dielectric breakdown strength. Fourthly, natural, nature-inspired, and common-commodity semiconductors are presented that broaden the materials base for organic semiconductors and may inspire further work to identify semiconductors that are stable in the face of changing environmental conditions yet degradable at the end of their product lifetime. Sustainability in organic electronics, energy storage, and emerging concepts will also be reviewed briefly. Research on “exotic” organic materials may ultimately result in environmentally safe “green electronic” products.



Dezember 2010 - Front Cover Advanced Functional Materials

Biocompatible and Biodegradable Materials for Organic Field-Effect Transistors

Biocompatible-ingestible electronic circuits and capsules for medical diagnosis and monitoring are currently based on traditional silicon technology. Organic electronics has huge potential for developing biodegradable, biocompatible, bioresorbable, or even metabolizable products. An ideal pathway for such electronic devices involves fabrication with materials from nature, or materials found in common commodity products. Transistors with an operational voltage as low as 4–5 V, a source drain current of up to 0.5 μA and an on-off ratio of 3–5 orders of magnitude have been fabricated with such materials. This work comprises steps towards environmentally safe devices in low-cost, large volume, disposable or throwaway electronic applications, such as in food packaging, plastic bags, and disposable dishware. In addition, there is significant potential to use such electronic items in biomedical implants.



May 2010 - Front Cover Advanced Materials

Arrays of Ultracompliant Electrochemical Dry Gel Cells for Stretchable Electronics

The front cover illustrates an ultracompliant battery for powering stretchable electronic items useful in wearable and comfortable electronic items integrated into clothing or implants. The battery combines acrylic elastomers with functional gel electrodes and withstands stretch ratios up to 100%. Shown is a series connection of two batteries, sufficient for driving a green light-emitting diode.



September 2009 - Inside Front Cover Advanced Materials

Light- and Touch-Point Localization using Flexible Large Area Organic Photodiodes and Elastomer Waveguides

A homogeneous large area photodiode with high resistance electrodes can be used to trace the position of a localized light signal, thus allowing the easy fabrication of large area light- and touch-point sensors. A readout scheme is presented that allows a direct and simple recalculation of the coordinates from four current signals picked up at the edges of the device.



August 2006 - Cover Applied Physics Letters

Flexible ferroelectret field-effect transistor for large-area sensor skins and microphones

Ferroelectrets generate an electric field large enough to modulate the conductance of the source-drain channel of a thin-filmfield-effect transistor. Integrating a ferroelectret with a thin-film transistor produces a ferroelectret field-effect transistor. The authors made such transistors by laminating cellular polypropylene films and amorphous silicon thin-film transistors on polyimide substrates. They show that these ferrroelectret field-effect transistors respond in a static capacitive or dynamic piezoelectric mode. A touch sensor, a pressure-activated switch, and a microphone are demonstrated. The structure can be scaled up to large-area flexible transducer arrays, such as roll-up steerable compliant sensor skin.