Christian Dürager

Bio: Christian Dürager is an academic researcher from Swiss Federal Laboratories for Materials Science and Technology. The author has contributed to research in topics: PMUT & Energy harvesting. The author has an hindex of 2, co-authored 4 publications receiving 36 citations.

Electroactive polymers as a novel actuator technology for lighter-than-air vehicles

Abstract: In this paper the worldwide first EAP actuated blimp will be presented. It consists of a slightly pressurized Helium filled body of a biologically inspired form with Dielectric Elastomer (DE) actuators driving a classical cross tail with two vertical and horizontal rudders for flight control. Two versions of actuators will be discussed: The first version consisted of "spring-roll" type of cylindrical actuators placed together with the electrical supply and control unit in the pay load gondola. The second version consisted of a configuration, where the actuators are placed between the control surfaces and the rudders. This novel type of EAP actuator named "active hinge" was developed and characterized first in the laboratory and afterwards optimized for minimum weight and finally integrated in the blimp structure. In the design phase a numerical simulation tool for the prediction of the DE actuators was developed based on a material model calibrated with the test results from cylindrical actuators. The electrical supply and control system was developed and optimized for minimum of weight. Special attention was paid to the electromagnetic systems compatibility of the high voltage electrical supply system of the DE actuators and the radio flight control system. The design and production of this 3.5 meter long Lighter-than-Air vehicle was collaboration between Empa Duebendorf Switzerland and the Technical University of Berlin. The first version of this EAP blimp first flew at an RC airship regatta hold on 24th of June 2006 in Dresden Germany, while the second version had his maiden flight on 8th of January 2007 in Duebendorf Switzerland. In both cases satisfactory flight control performances were demonstrated.

A wireless sensor system for structural health monitoring with guided ultrasonic waves and piezoelectric transducers

Abstract: Piezoelectric transducers are widely used for structural health monitoring (SHM) applications. Low weight and small dimensions are only two of the several advantages of piezoelectric transducers. However, these advantages are weakened by using wired connections for supplying the piezoelectric transducers. Besides the additional weight, a long wire connection can have an influence on the measured capacitance. Due to the aforementioned disadvantages, researchers developed different wireless solutions for SHM applications in the last 10 years. In this paper, we present a wireless SHM system, which is designed for SHM applications with piezoelectric transducers and guided ultrasonic waves (GUW). The first part in this paper describes the different parts of the wireless SHM system. One novelty ofthe proposed wireless system is that every wireless signal-processing unit (SPU) in the network can be used for exciting the piezoelectric transducer and also for measuring the voltage signals coming from the piezoelec...

Energy harvesting for wireless sensors by using piezoelectric transducers

Abstract: Wireless sensor technology, which integrates transducers, measurement electronics and wireless communication, has become increasingly vital in structural health monitoring (SHM) applications. Compared to traditional wired systems, wireless solutions reduce the installation time and costs and are not subjected to breakage caused by harsh weather conditions or other extreme events. Because of the low installation costs, wireless sensor networks allow the deployment of a big number of wireless sensor nodes on the structures. Moreover, the nodes can be placed on particularly critical components of the structure difficult to reach by wires. In most of the cases the power supply are conventional batteries, which could be a problem because of their finite life span. Furthermore, in the case of wireless sensor nodes located on structures, it is often advantageous to embed them, which makes an access impossible. Therefore, if a method of obtaining the untapped energy surrounding these sensors was implemented, significant life could be added to the power supply. Various approaches to energy harvesting and energy storage are discussed and limitations associated with the current technology are addressed. In this paper we first discuss the research that has been performed in the area of energy harvesting for wireless sensor technologies by using the ambient vibration energy. In many cases the energy produced by the ambient vibrations is far too small to directly power a wireless sensor node. Therefore, in a second step we discuss the development process for an electronic energy harvesting circuit optimized for piezoelectric transducers. In the last part of this paper an experiment with different piezoelectric transducers and their applicability for energy harvesting applications on vibrating structures will be discussed.

Elektronisches Messsystem zur Strukturzustandsüberwachung / Electronic Measurement System for Structural Health Monitoring

Abstract: Zusammenfassung Zur Überwachung von Faserverbundlösungen aus kohle- oder glasfaserverstärktem Kunststoff sind neue Ansätze notwendig. Der Artikel beschreibt ein elektronisches Messsystem zur integrierten Strukturzustandsüberwachung. Neben dem universalen Einsatz werden im ersten Teil der Aufbau des Systems sowie die mess- und signaltechnischen Eigenschaften beschrieben. In zweiten Teil wird die algorithmische Auswertung der Messsignale mit der „Empirical Mode Decomposition“-Methode erläutert. Mit der Ellipsen- Triangulationsmethode lassen sich in einem Versuchsaufbau Schädigungen durch Hagelkörner mit einem Durchmesser von 2 cm in einer Karbonplatte mit einem Durchmesser von 1m und einer Dicke von 1mm auf 3mm genau lokalisieren. Summary Novel approaches are required to monitor carbon or glass fiber composite solutions. This article describes an electronic measurement system for integrated structural analysis. The first part explains the universal application, measurement, and signal characteristics of the system. The second part explains the algorithmic analysis of the measurement signals with the “empirical mode decomposition” method. The ellipses triangulation algorithm is applied to a 1-mm-thick carbon plate (diameter 1m) damaged by hailstones of diameter 2 cm. The algorithm localizes the damage with an accuracy of 3 mm.

Advances in dielectric elastomers for actuators and artificial muscles.

Abstract: A number of materials have been explored for their use as artificial muscles Among these, dielectric elastomers (DEs) appear to provide the best combination of properties for true muscle-like actuation DEs behave as compliant capacitors, expanding in area and shrinking in thickness when a voltage is applied Materials combining very high energy densities, strains, and efficiencies have been known for some time To date, however, the widespread adoption of DEs has been hindered by premature breakdown and the requirement for high voltages and bulky support frames Recent advances seem poised to remove these restrictions and allow for the production of highly reliable, high-performance transducers for artificial muscle applications

Morphing aircraft based on smart materials and structures: A state-of-the-art review:

Abstract: A traditional aircraft is optimized for only one or two flight conditions, not for the entire flight envelope. In contrast, the wings of a bird can be reshaped to provide optimal performance at all...

TiO2?nanoparticles modified polydimethylsiloxane with fast response time and increased dielectric constant

Abstract: Polymer nanocomposite has shown great potential and impact on a broad range of techniques since its properties can be tailored by nano-fillers. This paper reports a polymer nanocomposite with enhanced electro-mechanical performance by mixing TiO2 nanoparticles into polydimethylsiloxane. Nanocomposites with particle concentration up to 30 wt% were prepared. High energy ball milling and polyether-modified silicone dispersant were used to suppress the agglomeration and ensure a stable dispersion. Properties of the nanocomposites, i.e. elastic modulus, response time, dielectric constant and optical transmittance, were tuned by modifying the particle concentration. Optimized electro-mechanical properties were observed at 5 wt% TiO2 particles. This nanocomposite was applied to a MEMS spatial light modulator, which was fabricated using micro-machining technology. The device was driven by a 200 V dc voltage and had a response time of 6 µs.

Dielectric Elastomers for Actuators and Artificial Muscles

Abstract: A number of electroactive polymers have been explored for their use as artificial muscles. Among these, dielectric elastomers appear to provide the best combination of properties for true muscle-like actuation. Dielectric elastomers behave as compliant capacitors, expanding in area and shrinking in thickness when a voltage is applied. Materials combining very high energy densities, strains and efficiencies have been known for some time. To date, however, the widespread adoption of dielectric elastomers has been hindered by premature breakdown and the requirement for high voltages and bulky support frames. Recent advances seem poised to remove these restrictions and allow for the production of highly reliable, high-performance transducers for artificial muscle applications.