TY - JOUR A1 - Wegener, Michael A1 - Hesse, J. A1 - Wegener, T. A1 - Gerhard, Reimund T1 - Patterned ferro-, pyro- and piezoelectricity in poly(vinylindene fluoride) by means of a laser-induced irreversible beta to alpha phase transformation Y1 - 2002 ER - TY - JOUR A1 - Wegener, Michael A1 - Hesse, J. A1 - Wegener, T. A1 - Gerhard, Reimund T1 - Patterned ferro-, pyro- and piezoelectricity in poly(vinylindene fluoride) by means of a laser-induced irreversible beta to alpha phase transformation [Erratum] Y1 - 2002 ER - TY - THES A1 - Wegener, Michael T1 - Ferroelektrete und Polymerschäume: Präparation, Eigenschaften und Anwendung als piezoelektrische Wandler Y1 - 2007 CY - Potsdam ER - TY - JOUR A1 - Tuncer, Enis A1 - Wegener, Michael T1 - Elastic properties of highly anisotropic thin poly(propylene) foams N2 - In this letter, elastic properties of highly anisotropic cellular poly(propylene) films are reported. The material shows peculiar elastic properties compared to other foams in the literature. The data is displayed as the relative Young's modulus E*/E-s versus relative density rho*/rho(s). Almost all the data from the literature are located on the region E*/E-s = (rho*/rho(s))(n) with 1 less than or equal to n less than or equal to 6. The introduced material on the other hand has lower relative Young's modulus at high relative densities, n greater than or equal to 6. (C) 2004 Elsevier B.V. All rights reserved Y1 - 2004 SN - 0167-577X ER - TY - JOUR A1 - Wegener, Michael A1 - Wirges, Werner A1 - Tiersch, Brigitte T1 - Porous polytetrafluoroethylene (PTFE) electret films : porosity and time dependent charging behaviour of the free surface N2 - Electrically charged porous polytetrafluoroethylene (PTFE) films are often discussed as active layers for electromechanical transducers. Here, the electric charging behavior of open-porous PTFE films with different porosities is investigated. Optimized electric charging of porous PTFE films is determined by variation of charging parameters such as electric fields and charging times. Maximum surface potentials are depending on the porosity of the PTFE films. Suitable charging leads to high surface potentials observed on non-stretched or slightly stretched porous PTFE films. Further increase of charging fields yields decreasing values of the surface potential accompanied with an increase of conductivity. Y1 - 2006 UR - http://www.springerlink.com/content/601u86x365560515/ U6 - https://doi.org/10.1007/s10934-006-9015-0 ER - TY - JOUR A1 - Wang, Feipeng A1 - Frübing, Peter A1 - Wirges, Werner A1 - Gerhard, Reimund A1 - Wegener, Michael T1 - Enhanced Polarization in Melt-quenched and Stretched Poly(vinylidene Fluoride-Hexafluoropropylene) Films N2 - beta-phase poly(vinylidene fluoride-hexafluoropropylene) (P(VDF-HFP)) copolymer films were prepared by uniaxially stretching solution-cast or melt-quenched samples. Different preparation routes lead to different amounts of the crystalline alpha and beta phases in the films, as detected by means of Fourier-transform infrared spectroscopy and X-ray diffractometry. The beta phase is significantly enhanced in melt-quenched and stretched films in comparison to solution-cast and stretched films. This is particularly true for copolymer samples with higher HFP content. The beta- phase enhancement is also observed in ferroelectric-hysteresis experiments where a rather high polarization of 58 mC/ m(2) was found on melt-quenched and stretched samples after poling at electric fields of 140 MV/m. After poling at 160 MV/m, one of these samples exhibited a piezoelectric d(33) coefficient as high as 21 pC/N. An electric-field-induced partial transition from the alpha to the beta phase was also observed on the melt-quenched and stretched samples. This effect leads to a further increase in the applications-relevant dipole polarization. Uniaxially stretched ferroelectric- polymer films are highly anisotropic. Dielectric resonance spectroscopy reveals a strong increase of the transverse piezoelectric d(32) coefficient and a strong decrease of the transverse elastic modulus c(32) upon heating from 20 to 50 degrees C. Y1 - 2010 UR - http://ieeexplore.ieee.org/servlet/opac?punumber=94 U6 - https://doi.org/10.1109/TDEI.2010.5539679 SN - 1070-9878 ER - TY - JOUR A1 - Kussmaul, Björn A1 - Risse, Sebastian A1 - Wegener, Michael A1 - Kofod, Guggi A1 - Krüger, Hartmut T1 - Matrix stiffness dependent electro-mechanical response of dipole grafted silicones JF - Smart materials and structures N2 - The properties of dielectric elastomer actuators can be optimized by modifying the dielectric or mechanical properties of the dielectric elastomer. This paper presents the simultaneous control of both dielectric and mechanical properties, in a silicone elastomer network comprising cross-linker, chains and grafted molecular dipoles. Chains with two different molecular weights were each combined with varying amounts of grafted dipole. Chemical and physical characterization showed that networks with stoichiometric control of cross-linking density and permittivity were obtained, and that longer chain lengths resulted in higher electrical field response due to the reduction in cross-linking density and correspondingly in mechanical stiffness. Both actuation sensitivities were enhanced by 6.3 and 4.6 times for the short and long chain matrix material, respectively. Y1 - 2012 U6 - https://doi.org/10.1088/0964-1726/21/6/064005 SN - 0964-1726 VL - 21 IS - 6 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Ryabchun, Alexander A1 - Kollosche, Matthias A1 - Wegener, Michael A1 - Sakhno, Oksana T1 - Holographic Structuring of Elastomer Actuator: First True Monolithic Tunable Elastomer Optics JF - Advanced materials N2 - Volume diffraction gratings (VDGs) are inscribed selectively by diffusive introduction of benzophenone and subsequent UV-holographic structuring into an electroactive dielectric elastomer actuator (DEA), to afford a continuous voltage-controlled grating shift of 17%. The internal stress coupling of DEA and optical domain allows for a new generation of true monolithic tunable elastomer optics with voltage controlled properties. Y1 - 2016 U6 - https://doi.org/10.1002/adma.201602881 SN - 0935-9648 SN - 1521-4095 VL - 28 SP - 10217 EP - 10223 PB - Wiley-VCH CY - Weinheim ER - TY - THES A1 - Wegener, Michael T1 - Polungsverhalten und Depolarisierung ferroelektrischer und nicht ferroelektrischer Polymere Y1 - 1999 CY - Potsdam ER - TY - JOUR A1 - Weinhold, Till A1 - Wegener, Michael A1 - Künstler, Wolfgang A1 - Seiß, Martin A1 - Görne, Thomas A1 - Gerhard, Reimund T1 - Porous polytetrafluoroethylene (PTFE) single-film space-charge electrets with high piezoelectric coefficients Y1 - 2000 SN - 0537-9989 ER -