Siegfried Bauer

• Univ. Prof. Dr.
• Head of Department at Johannes Kepler University of Linz

Embedded sensors are key to optimizing processes and products; they collect data that allow time, energy, and materials to be saved, thereby reducing costs. After production, they remain in place and are used to monitor the long‐term structural health of buildings or aircraft. Fueled by climate change, sustainable construction materials such as woo...

Paper-Based Sensors iSens are flexible, foldable, and translucent paper-based sensors. The porous substrates consist of a fiber structure that is highly permeable to liquids. Interdigital electrodes made of ultrathin copper are individually designed by one step laser ablation. This iSens platform, presented by Martin Kaltenbrunner and co-workers in...

Nature offers bionic inspirations for elegant applications of mechanical principles such as the concept of snap buckling, which occurs in several plants. Exploiting mechanical instabilities is the key to fast movement here. We use the snap-through and snap-back instability observed in natural rubber balloons to design an ultrafast purely mechanical...

Biodegradable and biocompatible elastic materials for soft robotics, tissue engineering or stretchable electronics with good mechanical properties, tunability, modifiability or healing properties drive technological advance, and yet they are not durable under ambient conditions and do not combine all the attributes in a single platform. We have dev...

Stretchable Electronics The image, provided by Martin Kaltenbrunner and co‐workers (article number 2000065), shows magnetic interfaces serving not only as mechanical but also as electrical connectors in stretchable electronics. These connectors are safeguarded by a controlled release mechanism, preventing failure in every‐day operation and allow a...

Wearable healthcare devices monitor the condition of patients outside the hospital and hence increase treatment capacity and resources. At the same time, patients benefit from wireless data transmission and conformable device designs, speeding up the rehabilitation process and integration into normal daily activities. Yet, the successful implementa...

The image representing article number 2000467 by Martin Kaltenbrunner and co‐workers shows the mixing of the two phases that form a polyHIPE, a process in which UV‐curable monomers and an electrolyte solution are brought together, to form a highly porous, ion conductive structure. The use of such polyHIPEs as high‐performance separators in stretcha...

Powering soft embodiments of robots, machines and electronics is a key issue that impacts emerging human friendly forms of technologies. Batteries as energy source enable their untethered operation at high power density but must be rendered elastic to fully comply with (soft) robots and human beings. Current intrinsically stretchable batteries typi...

Rapid energy‐efficient movements are one of nature's greatest developments. Mechanisms like snap‐buckling allow plants like the Venus flytrap to close the terminal lobes of their leaves at barely perceptible speed. Here, a soft balloon actuator is presented, which is inspired by such mechanical instabilities and creates safe, giant, and fast deform...

Explosion of ping‐pong balls that is caused by the rapid inflation of an elastomer membrane. The illustrated ultrafast actuation is based on a plant‐inspired mechanical instability that occurs in natural rubber and can be remotely triggered, presented in article number 1903391 by Martin Kaltenbrunner and co‐workers. These new types of high‐speed so...

Flexible circuits: anodization makes them all! A simple concept of scanning head-guided anodization is shown to be highly expandable to fabricate various electronic components. A team led by Professor Siegfried Bauer from Johannes Kepler University Linz, Austria develops a universal and patternable printing protocol of anodic oxides for a full rang...

We present RESi (Resistive tExtile Sensor Interfaces), a novel sensing approach enabling a new kind of yarn-based, resistive pressure sensing. The core of RESi builds on a newly designed yarn, which features conductive and resistive properties. We run a technical study to characterize the behaviour of the yarn and to determine the sensing principle...

Expensive equipment is often considered a prerequisite for good science. But the development of technology that is affordable and accessible to many could help promote a greater diversity of scientific thinking.

In this paper, we describe the design, fabrication and functional principle of microfluidic diodes – devices for directional liquid transport. They are passive (i.e., need no external energy input) and are capable of unidirectional water transport even vertically against gravity, i.e. they prevent backflow of liquid. In designing the devices with a...

The article “Fluidic Diode” for Passive Unidirectional Liquid Transport Bioinspired by the Spermathecae of Fleas, written by Gerda Buchberger, Alexander Kogler, Agnes Weth, Richard Baumgartner, Philipp Comanns, Siegfried Bauer, Werner Baumgartner, was originally published electronically on the publisher’s internet portal (currently SpringerLink) on...

We present a device for passive unidirectional liquid transport. The capillary channels used are bioinspired by the shape of the spermathecae (receptaculum seminis) of rabbit fleas (Spilopsyllus cuniculi) and rat fleas (Xenopsylla cheopis). The spermatheca is an organ of female fleas that stores sperm until suitable conditions to lay eggs are found...

Controlling the size and shape of semiconducting nanocrystals advances nanoelectronics and photonics. Quantum-confined, inexpensive, solution-derived metal halide perovskites offer narrowband, color-pure emitters as integral parts of next-generation displays and optoelectronic devices. We use nanoporous silicon and alumina thin films as templates f...

Introducing methods for instant tough bonding between hydrogels and antagonistic materials—from soft to hard—allows us to demonstrate elastic yet tough biomimetic devices and machines with a high level of complexity. Tough hydrogels strongly attach, within seconds, to plastics, elastomers, leather, bone, and metals, reaching unprecedented interfaci...

A dielectric elastomer transducer is a deformable capacitor, and is under development as a sensor, actuator, or generator. Among various geometric configurations, laterally-constrained transducer, also known as pure-shear transducer, is easy to implement and effective to couple mechanical force and electrical voltage. This analytical study reveals...

Tuning the band gap of semiconductors via quantum size effects launched a technological revolution in optoelectronics, advancing solar cells, quantum dot light-emitting displays, and solid state lasers. Next generation devices seek to employ low-cost, easily processable semiconductors. A promising class of such materials are metal-halide perovskite...

This chapter presents a brief overview on sensor and transducer applications of piezoelectric and electrostrictive polymers. Piezoelectric and electrostrictive polymers are smart electromechanical materials which have already found commercial applications in various transducer configurations. Novel applications may arise in the emerging fields of a...

Large-bandwidth, low-operation-voltage, and uniform organic amplifiers are fabricated on ultrathin foils. By the integration of short-channel OTFTs and AlOx capacitors, organic amplifiers with a bandwidth of 25 kHz are realized, demonstrating the highest gain-bandwidth product (GBWP) reported to date. Owing to material and process advancements, clo...

We present light-point localization by transparent, flexible, thin sensor surfaces based on only two functional polymers: a thin film of pyroelectric poly(vinylidene fluoride) (PVDF) combined with large-area polymer electrodes made of poly(3,4-ethylene dioxythiophene):poly(styrene sulfonic acid) (PEDOT:PSS). One of the electrodes is resistive to en...

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 exhi...

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 exhi...

Supplementary

Supplementary

Ferroelectrets are used in capacitive piezoelectric sensors. When a force is applied to such a sensor, an electrical signal is generated. We first describe the equivalent circuit representation of a ferroelectret sensor element and proceed with the coupling of the sensor element to a measurement device. Based on the governing equations for the meas...

Ferroelectrets are used in capacitive piezoelectric sensors. When a force is applied to such a sensor, an electrical signal is generated. We first describe the equivalent circuit representation of a ferroelectret sensor element and proceed with the coupling of the sensor element to a measurement device. Based on the governing equations for the meas...

This chapter presents a brief overview on sensor and transducer applications of piezoelectric and electrostrictive polymers. Piezoelectric and electrostrictive polymers are smart electromechanical materials which have already found commercial applications in various transducer configurations. Novel applications may arise in the emerging fields of a...

Dielectric elastomer transducers consist of thin electrically insulating elastomeric membranes coated on both sides with compliant electrodes. They are a promising electromechanically active polymer technology that may be used for actuators, strain sensors, and electrical generators that harvest mechanical energy. The rapid development of this fiel...

The Texas Horned lizard has the ability to harvest moisture from ambience with its skin and to transport water directionally to its snout; at the same time water is hindered to flow in opposite direction. We present a passive microfluidic device for directional liquid transport which is inspired by this natural role model. To this end, we deduce a...

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), highl...

Moisture-harvesting lizards such as the Texas horned lizard (Iguanidae: Phrynosoma cornutum) live in arid regions. Special skin adaptations enable them to access water sources such as moist sand and dew: their skin is capable of collecting and transporting water directionally by means of a capillary system between the scales. This fluid transport i...

Low density energy sources, like wind and solar energy, are widely available and they are increasingly used for electricity conversion worldwide. Ambient energy sources with even lower energy densities are universally available and could equally be converted into electricity with large scale special purpose converter systems. This work discusses a...

Glassy metallic Hf thin films were obtained using electron beam deposition at room temperature due to the low energy received by Hf atoms during the film formation process. The amorphous nature of the Hf films suggested by XRD was confirmed by low temperature electrical conductivity measurements where a negative temperature coefficient of resistivi...

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 compl...

Electronics formed on ultrathin polymer supports are extremely lightweight, able to float on a soap bubble. On page 34, M. Drack and co‐workers describe the fabrication of this imperceptible electronic technology platform together with applications in spatio‐temporal temperature mapping of electronic circuitry, food items, or human skin. In conjunc...

Laser ultrasonic (LUS) receivers based on photorefractive (PR) materials are contactless and adap-tive interferometers, which are used widely for materials characterization. Here, we present a simple LUS interferometer at 532 nm operating wavelength based on organic PR polymer composites (PVK/ECZ/C60) doped with the nonlinear chromophore 4-[4-(diet...

The rapid and efficient development of soft active materials requires readily available, compact testing equipment. We propose a desktop-sized, cost-efficient, and open source radial stretching system as an alternative to commercially available biaxial and uniaxial stretching devices. It allows for doubling the diameter of an elastomer membrane whi...

Ferroelectrets are flexible and conformable polymer transducer foils with a dominant longitudinal piezoelectric effect. Ferroelectrets also have a negligible transverse piezoelectric effect, which makes them ideal for the fabrication of roll- and bendable keyboards. Cellular polypropylene ferroelectrets with heteropolar charge patterns are useful f...

Supplementary

Supplementary

Supplementary

Supplementary

Supplementary

New polymerisable photoluminescent octahedral rhenium cluster complexes trans-[{Re6Q8}(TBP)4(VB)2] (Q = S or Se; TBP – p-tert-buthylpyridine; VB – vinyl benzoate) have been synthesised, characterised and used to construct rhenium cluster-organic polymer hybrid materials. These novel polymer systems are solution-processable and the rhenium clusters...

Clean, renewable and abundant sources of energy, such as the vast energy of ocean waves, are untapped today, because no technology exists to convert such mechanical motions to electricity economically. Other sources of mechanical energy, such as motions of people and vibrations of buildings and bridges, can potentially power portable electronics an...

Dielectric elastomer minimum energy structures (DEMES) are soft electronic transducers and energy harvesters with potential for consumer goods. The temporal change in their electromechanical properties is of major importance for engineering tasks. Therefore, we study acrylic DEMES by impedance spectroscopy and by optical methods for a total time pe...

We report on a contactless method to focus laser generated bulk and surface ultrasound waves in the thermo-elastic coupling mode by annular shaped illumination. By using a spatial light modulator (SLM) the beam profile of a pulsed picoseconds laser was shaped to annular forms flexibly and further rings with a thickness of 50 μm and a generation ene...

Microelectronics dominates the technological and commercial landscape of today's electronics industry; ultrahigh density integrated circuits on rigid silicon provide the computing power for smart appliances that help us organize our daily lives. Integrated circuits function flawlessly for decades, yet we like to replace smart phones and tablet comp...

We present two laser ultrasonic receivers based on organic photorefractive polymer composites with 2-[4-bis(2-methoxyethyl)aminobenzylidene]malononitrile (AODCST) or 2-dicyanomethylen-3-cyano-5,5-dimethyl-4-(4′-dihexylaminophenyl)-2,5-dihydrofuran nonlinear optical chromophores. Experimental results show sensitivities of the ultrasonic receivers of...

This paper shows that a highly deformable capacitor made of a soft dielectric and two conformal electrodes can switch between two states discontinuously, by a first-order transition, as the total charge varies gradually. When the total charge is small, it spreads evenly over the area of the capacitor, and the capacitor deforms homogeneously. When t...

Scientists are exploring elastic and soft forms of robots, electronic skin and energy harvesters, dreaming to mimic nature and to enable novel applications in wide fields, from consumer and mobile appliances to biomedical systems, sports and healthcare. All conceivable classes of materials with a wide range of mechanical, physical and chemical prop...

Dielectric elastomers are used for electromechanical energy conversion in actuators and in harvesting mechanical energy from renewable sources. The electrical breakdown strength determines the limit of a dielectric elastomer for its use in actuators and energy harvesters. We report two experimental configurations for the measurement of the stretch...

Skin is a large, flexible and robust organ that covers and protects the body from external damage. This multifunctional biological model is inspiring the development of electronic equivalents referred to as 'electronic skin', consisting of large-area networks of sensors that detect pressure, temperature and other environmental stimuli, and are usua...

We demonstrate ultrathin (2 µm thick) red and orange polymer light-emitting diodes with unprecedented mechanical properties in terms of their flexibility and ability to be stretched. The devices have a luminance greater than 100 cd m–2, sufficient for a variety of optoelectronic applications including indoor displays. They can be operated as free-s...

The dataset is a video file (also available here: http://youtu.be/_wcaYDxi5_8) showing the use of our screen printed, flexible, large area polymer sensors in safety systems for automotive applications. The sensors were developed within the European Project 3PLAST. The pyroelectric and piezoelectric effect of the ferroelectric polymer is utilized to...

Hydroxyapatite nanocrystals in natural form are a major component of bone- a known piezoelectric material. Synthetic hydroxyapatite is widely used in bone grafts and prosthetic pyroelectric coatings as it binds strongly with natural bone. Nanocrystalline synthetic hydroxyapatite films have recently been found to exhibit strong piezoelectricity and...

Electronic devices have advanced from their heavy, bulky origins to become smart, mobile appliances. Nevertheless, they remain rigid, which precludes their intimate integration into everyday life. Flexible, textile and stretchable electronics are emerging research areas and may yield mainstream technologies. Rollable and unbreakable backplanes with...

We report on a contactless laser ultrasonic (LUS) method to monitor the phase transformation in a titanium alloy (Ti-6%Al-4%V) sheet by using a simple and high resolution LUS interferometer, based on two wave mixing in a fast BSO photorefractive crystal. The temperature dependent phase transformation from the α to the β phase in the Ti samples was...

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...

Fluorescent foils are used with silicon photodiodes for large-area detection of objects, when combined with lasers forming a light curtain. An object entering the detection area penetrates the light curtain and casts shadows onto the fluorescent foils. Using a simple mathematical algorithm, the position of the object is detected with high speed. Th...

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...

Recent work is reviewed on organic solar cells thinner than a thread of spider silk, so flexible that they can be wrapped firmly around a human hair, lighter than autumn leaves and with an unprecedented specific weight of 10 W/g. Solar cell fabrication is based on planar process technologies only, commonly employed in semiconductor industry. The sa...

Hydrogen-bonding (H-bonding) is a relatively strong, highly directional, and specific noncovalent interaction present in many organic molecules, and notably is responsible for supramolecular ordering in biological systems. The H-bonding interactions play a role in many organic electrically conducting materials – in particular in those related to bi...

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 re...

Perhaps the same materials used in printer inks and hair dyes can be employed in future electronic technologies? The front cover illustrates the use of hydrogen-bonded pigments, well-established printing inks, in organic electronic circuits. On page 1563, Eric Daniel Głowacki and co-workers present a new perspective for the design of stable organic...

Dielectric elastomer actuators are considered as promising candidates for robotic elements. To this end planar dielectric elastomer actuators and dielectric elastomer minimum energy structures are applicable. The knowledge of their electrical and mechanical characteristics is very important for engineering tasks. Therefore we study these actuators...

Films made of 2D networks of single-walled carbon nanotubes (SWNTs) are one of the most promising active-channel materials for field-effect transistors (FETs) and have a variety of flexible electronic applications, ranging from biological and chemical sensors to high-speed switching devices. Challenges, however, still remain due to the current hyst...

Dielectric elastomers are capable of large voltage-induced deformation, but achieving such large deformation in practice has been a major challenge due to electromechanical instability and electric breakdown. The complex nonlinear behavior suggests an important opportunity: electromechanical instability can be harnessed to achieve giant voltage-ind...

Biological materials in organic electronics stand for low-cost production of biocompatible, biodegradable, and sustainable electronic devices. In this chapter, we discuss such materials and their implementation in the fabrication of electronic circuits. We briefly introduce applications of such biocompatible and biodegradable materials for interfac...

Introduction Radio Frequency Power Supplies Power Generation Power Storage Summary Acknowledgments References

We investigate the dielectric response of solar cell devices based on oxygen-doped poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) blends as a function of temperature between 133K and 303K. The spectra are analyzed using a recently introduced model [ O. Armbruster, C. Lungenschmied and S. Bauer Phys. Rev. B 84 085208 (...

We describe the history of indigo dye and its derivative Tyrian purple, from their roles in the ancient world to recent research showing the semiconducting properties of indigoids. Indigoids are natural dyes that have been produced for centuries, and indigo is currently the most produced dye worldwide. Herein we review the history of these material...

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....

Dielectric elastomer actuators (DEAs) are considered as promising candidates for biomimetic robotic elements. For these robotic elements planar dielectric elastomer actuators (p-DEAs) and dielectric elastomer minimum energy structures (DEMES) are applicable. However, the knowledge of their electrical and mechanical characteristics is of major impor...

We present a flexible polymer sensor for light point localization based on the pyroelectric polymer poly(vinylidene fluoride) (PVDF) in combination with large area resistive electrodes. This large area sensor is simple in design; a division of the sensor surface into an array of individual sensor elements as used in active matrix technology is avoi...

Quinacridone is a five-ring hydrogen-bonded molecule analogous in structure and size to the well-known organic semiconductor pentacene. Unlike pentacene, quinacridone has limited intramolecular π-conjugation and becomes highly colored in the solid state due to strong intermolecular electronic coupling. We found that quinacridone shows a field-effec...

We live in a world where the lifetime of electronics is becoming shorter, now approaching an average of several months. This poses a growing ecological problem. This brief review will present some of the initial steps taken to address the issue of electronic waste with biodegradable organic electronic materials. Many organic materials have been sho...

We report on the fabrication and performance of vacuum-processed organic field effect transistors utilizing evaporated low-density polyethylene (LD-PE) as a dielectric layer. With C60 as the organic semiconductor, we demonstrate low operating voltage transistors with field effect mobilities in excess of 4 cm2/Vs. Devices with pentacene showed a mob...

Dielectric elastomer generators are high-energy-density electromechanical transducers. Their performance is affected by dissipative losses. This paper presents a theoretical analysis of a dielectric elastomer generator with two dissipative processes: viscoelasticity and current leakage. Conversion cycles are shown to attain steady-state after sever...