title: Nonlinear control of high-frequency phonons in spider silk.
abstract: Spider dragline silk possesses superior mechanical properties compared with synthetic polymers with similar chemical structure due to its hierarchical structure comprised of partially crystalline oriented nanofibrils. To date, silk's dynamic mechanical properties have been largely unexplored. Here we report an indirect hypersonic phononic bandgap and an anomalous dispersion of the acoustic-like branch from inelastic (Brillouin) light scattering experiments under varying applied elastic strains. We show the mechanical nonlinearity of the silk structure generates a unique region of negative group velocity, that together with the global (mechanical) anisotropy provides novel symmetry conditions for gap formation. The phononic bandgap and dispersion show strong nonlinear strain-dependent behaviour. Exploiting material nonlinearity along with tailored structural anisotropy could be a new design paradigm to access new types of dynamic behaviour.
authors.affiliation: Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
authors.forename: Dirk
authors.initials: D
authors.lastname: Schneider
authors.affiliation: Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Gomopoulos
authors.affiliation: Functional and Smart Materials Laboratory, Emerging Systems, DSO National Laboratories, S117605 Singapore, Singapore.
authors.forename: Cheong Y
authors.initials: CY
authors.lastname: Koh
authors.affiliation: Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.|Department of Physics, University of Ioannina, 45110 Ioannina, Greece.
authors.forename: Periklis
authors.initials: P
authors.lastname: Papadopoulos
authors.affiliation: Institute of Experimental Physics I, Linnéstr. 5, University of Leipzig, 04103 Leipzig, Germany.
authors.forename: Friedrich
authors.initials: F
authors.lastname: Kremer
authors.affiliation: Department of Materials Science and Nano-Engineering, Rice University, Houston, Texas 77030, USA.
authors.forename: Edwin L
authors.initials: EL
authors.lastname: Thomas
authors.affiliation: Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.|Department of Materials Science University of Crete and IESL-F.O.R.T.H, 77110 Heraklion, Greece.
authors.forename: George
authors.initials: G
authors.lastname: Fytas