@article{ZhaoDunlopQiuetal.2014,
  author    = {Zhao, Qiang and Dunlop, John William Chapman and Qiu, Xunlin and Huang, Feihe and Zhang, Zibin and Heyda, Jan and Dzubiella, Joachim and Antonietti, Markus and Yuan, Jiayin},
  title     = {An instant multi-responsive porous polymer actuator driven by solvent molecule sorption},
  series = {Nature Communications},
  volume    = {5},
  journal   = {Nature Communications},
  publisher = {Nature Publ. Group},
  address   = {London},
  issn      = {2041-1723},
  doi       = {10.1038/ncomms5293},
  pages     = {8},
  year      = {2014},
  abstract  = {Fast actuation speed, large-shape deformation and robust responsiveness are critical to synthetic soft actuators. A simultaneous optimization of all these aspects without trade-offs remains unresolved. Here we describe porous polymer actuators that bend in response to acetone vapour (24 kPa, 20 degrees C) at a speed of an order of magnitude faster than the state-of-the-art, coupled with a large-scale locomotion. They are meanwhile multi-responsive towards a variety of organic vapours in both the dry and wet states, thus distinctive from the traditional gel actuation systems that become inactive when dried. The actuator is easy-to-make and survives even after hydrothermal processing (200 degrees C, 24 h) and pressing-pressure (100 MPa) treatments. In addition, the beneficial responsiveness is transferable, being able to turn 'inert' objects into actuators through surface coating. This advanced actuator arises from the unique combination of porous morphology, gradient structure and the interaction between solvent molecules and actuator materials.},
  language  = {en}
}
@article{SborikasQiuWirgesetal.2014,
  author    = {Sborikas, Martynas and Qiu, Xunlin and Wirges, Werner and Gerhard, Reimund and Jenninger, Werner and Lovera, Deliani},
  title     = {Screen printing for producing ferroelectret systems with polymer-electret films and well-defined cavities},
  series = {Applied physics : A, Materials science \& processing},
  volume    = {114},
  journal   = {Applied physics : A, Materials science \& processing},
  number    = {2},
  publisher = {Springer},
  address   = {New York},
  issn      = {0947-8396},
  doi       = {10.1007/s00339-013-7998-3},
  pages     = {515 -- 520},
  year      = {2014},
  abstract  = {We report a process for preparing polymer ferroelectrets by means of screen printing-a technology that is widely used for the two-dimensional patterning of printed layers. In order to produce polymer-film systems with cavities that are suitable for bipolar electric charging, a screen-printing paste is deposited through a screen with a pre-designed pattern onto the surface of a polymer electret film. Another such polymer film is placed on top of the printed pattern, and well-defined cavities are formed in-between. During heating and curing, the polymer films are tightly bonded to the patterned paste layer so that a stable three-layer system is obtained. In the present work, polycarbonate (PC) films have been employed as electret layers. Screen printing, curing and charging led to PC ferroelectret systems with a piezoelectric d (33) coefficient of about 28 pC/N that is stable up to 100 C-a similar to. Due to the rather soft patterned layer, d (33) strongly decreases already for static pressures of tens of kPa. The results demonstrate the suitability of screen printing for the preparation of ferroelectret systems.},
  language  = {en}
}
@article{QiuWirgesGerhard2014,
  author    = {Qiu, Xunlin and Wirges, Werner and Gerhard, Reimund},
  title     = {Polarization and Hysteresis in Tubular-Channel Fluoroethylenepropylene-Copolymer Ferroelectrets},
  series = {Ferroelectrics},
  volume    = {472},
  journal   = {Ferroelectrics},
  number    = {1},
  publisher = {Routledge, Taylor \& Francis Group},
  address   = {Abingdon},
  issn      = {0015-0193},
  doi       = {10.1080/00150193.2014.964603},
  pages     = {100 -- 109},
  year      = {2014},
  abstract  = {Polarization-vs.-applied-voltage hysteresis curves are recorded on tubular-channel fluoroethylene-propylene (FEP) copolymer ferroelectrets by means of a modified Sawyer-Tower circuit. Dielectric barrier discharges (DBDs) inside the cavities are triggered when the applied voltage is sufficiently high. During the DBDs, the cavities become man-made macroscopic dipoles which build up an effective polarization in the ferroelectret. Therefore, a phenomenological hysteresis curve is observed. From the hysteresis loop, the remanent polarization and the coercive field can be determined. Furthermore, the polarization can be related to the respective piezoelectric coefficient of the ferroelectret. The proposed method is easy to implement and is useful for characterization, further development and optimization of ferro- or piezoelectrets.},
  language  = {en}
}