skip to main content

Title: Optically switchable natural silk

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