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Title: Optically switchable natural silk

Abstract

An optically active bio-material is created by blending natural silk fibers with photoisomerizable chromophore molecules—azobenzenebromide (AzBr). The material converts the energy of unpolarized light directly into mechanical work with a well-defined direction of action. The feasibility of the idea to produce optically driven microsized actuators on the basis of bio-material (silk) is proven. The switching behavior of the embedded AzBr molecules was studied in terms of UV/Vis spectroscopy. To test the opto-mechanical properties of the modified fibers and the structural changes they undergo upon optically induced switching, single fiber X-ray diffraction with a micron-sized synchrotron radiation beam was combined in situ with optical switching as well as with mechanical testing and monitoring. The crystalline regions of silk are not modified by the presence of the guest molecules, hence occupy only the amorphous part of the fibers. It is shown that chromophore molecules embedded into fibers can be reversibly switched between the trans and cis conformation by illumination with light of defined wavelengths. The host fibers respond to this switching with a variation of the internal stress. The amplitude of the mechanical response is independent of the applied external stress and its characteristic time is shorter than the relaxation time ofmore » the usual mechanical response of silk.« less

Authors:
;  [1];  [2]; ; ;  [1];  [3]; ;  [4];  [3];  [5]
  1. Institut für Experimentelle und Angewandte Physik, Universität Kiel, D-24098 Kiel (Germany)
  2. (HZG), D-21502 Geesthacht (Germany)
  3. Institute of Materials Research, Helmholtz-Zentrum Geesthacht (HZG), D-21502 Geesthacht (Germany)
  4. Institut für Materialwissenschaft, Universität Kiel, D-24098 Kiel (Germany)
  5. (Germany)
Publication Date:
OSTI Identifier:
22412782
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 106; Journal Issue: 9; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ACTUATORS; DIRECT ENERGY CONVERSION; FIBERS; ILLUMINANCE; MECHANICAL PROPERTIES; MOLECULES; MONITORING; ORGANIC BROMINE COMPOUNDS; RELAXATION TIME; RESIDUAL STRESSES; SPECTROSCOPY; SYNCHROTRON RADIATION; VARIATIONS; VISIBLE RADIATION; X-RAY DIFFRACTION

Citation Formats

Krasnov, Igor, E-mail: Igor.Krasnov@hzg.de, Müller, Martin, E-mail: Martin.Mueller@hzg.de, Institute of Materials Research, Helmholtz-Zentrum Geesthacht, Krekiehn, Nicolai R., Jung, Ulrich, Magnussen, Olaf M., Krywka, Christina, Zillohu, Ahnaf U., Strunskus, Thomas, Elbahri, Mady, and Institut für Materialwissenschaft, Universität Kiel, D-24098 Kiel. Optically switchable natural silk. United States: N. p., 2015. Web. doi:10.1063/1.4913912.
Krasnov, Igor, E-mail: Igor.Krasnov@hzg.de, Müller, Martin, E-mail: Martin.Mueller@hzg.de, Institute of Materials Research, Helmholtz-Zentrum Geesthacht, Krekiehn, Nicolai R., Jung, Ulrich, Magnussen, Olaf M., Krywka, Christina, Zillohu, Ahnaf U., Strunskus, Thomas, Elbahri, Mady, & Institut für Materialwissenschaft, Universität Kiel, D-24098 Kiel. Optically switchable natural silk. United States. doi:10.1063/1.4913912.
Krasnov, Igor, E-mail: Igor.Krasnov@hzg.de, Müller, Martin, E-mail: Martin.Mueller@hzg.de, Institute of Materials Research, Helmholtz-Zentrum Geesthacht, Krekiehn, Nicolai R., Jung, Ulrich, Magnussen, Olaf M., Krywka, Christina, Zillohu, Ahnaf U., Strunskus, Thomas, Elbahri, Mady, and Institut für Materialwissenschaft, Universität Kiel, D-24098 Kiel. Mon . "Optically switchable natural silk". United States. doi:10.1063/1.4913912.
@article{osti_22412782,
title = {Optically switchable natural silk},
author = {Krasnov, Igor, E-mail: Igor.Krasnov@hzg.de and Müller, Martin, E-mail: Martin.Mueller@hzg.de and Institute of Materials Research, Helmholtz-Zentrum Geesthacht and Krekiehn, Nicolai R. and Jung, Ulrich and Magnussen, Olaf M. and Krywka, Christina and Zillohu, Ahnaf U. and Strunskus, Thomas and Elbahri, Mady and Institut für Materialwissenschaft, Universität Kiel, D-24098 Kiel},
abstractNote = {An optically active bio-material is created by blending natural silk fibers with photoisomerizable chromophore molecules—azobenzenebromide (AzBr). The material converts the energy of unpolarized light directly into mechanical work with a well-defined direction of action. The feasibility of the idea to produce optically driven microsized actuators on the basis of bio-material (silk) is proven. The switching behavior of the embedded AzBr molecules was studied in terms of UV/Vis spectroscopy. To test the opto-mechanical properties of the modified fibers and the structural changes they undergo upon optically induced switching, single fiber X-ray diffraction with a micron-sized synchrotron radiation beam was combined in situ with optical switching as well as with mechanical testing and monitoring. The crystalline regions of silk are not modified by the presence of the guest molecules, hence occupy only the amorphous part of the fibers. It is shown that chromophore molecules embedded into fibers can be reversibly switched between the trans and cis conformation by illumination with light of defined wavelengths. The host fibers respond to this switching with a variation of the internal stress. The amplitude of the mechanical response is independent of the applied external stress and its characteristic time is shorter than the relaxation time of the usual mechanical response of silk.},
doi = {10.1063/1.4913912},
journal = {Applied Physics Letters},
number = 9,
volume = 106,
place = {United States},
year = {Mon Mar 02 00:00:00 EST 2015},
month = {Mon Mar 02 00:00:00 EST 2015}
}
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  • Strong and tough epoxy composites are developed using a less-studied fibre reinforcement, that of natural silk. Two common but structurally distinct silks from the domestic B. mori/Bm and the wild A. pernyi/Ap silkworms are selected in fabric forms. We show that the toughening effects on silk-epoxy composites or SFRPs are dependent on the silk species and the volume fraction of silk. Both silks enhance the room-temperature tensile and flexural mechanical properties of the composite, whereas the more resilient Ap silk shows a more pronounced toughening effect and a lower critical reinforcement volume for the brittle-ductile transition. Specifically, our 60 vol.%more » Ap-SFRP displays a three-fold elevation in tensile and flexural strength, as compared to pure epoxy resin, with an order of magnitude higher breaking energy via a distinct, ductile failure mode. Importantly, the 60 vol.% Ap-SFRP remains ductile with 7% flexural elongation at lower temperatures (-50 °C). Under impact, these SFRPs show significantly improved energy absorption, and the 60 vol.% Ap-SFRP has an impact strength some eight times that of pure epoxy resin. Lastly, the findings demonstrate both marked toughening and strengthening effects for epoxy composites from natural silk reinforcements, which presents opportunities for mechanically superior and "green" structural composites.« less