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Journal of Biotechnology and Phytochemistry
Volume 1 Issue 3 Chemistry World 2017
Page 71
November 13-15, 2017 Athens, Greece
7th World Congress on
Chemistry
Soft based hypersonic phononics
Y Cang, B Graczykowski and G Fytas
Max Planck Institute for Polymer Research, Germany
Phononic structures (composite materials in which a
periodic distribution of elastic parameters facilitates control
of the propagation of phonons, hold the promise to enable
transformative material technologies in areas ranging from
acoustic and thermal cloaking to thermoelectric devices. This
requires strategies to deliberately ‘engineer’ the phononic
band structure of materials in the frequency range of interest.
Phononics, the acoustic equivalents of the photonics, are
controlled by a larger number of material parameters, as
phonon cannot propagate in vacuum. The study of hypersonic
phononics (hPnC) imposes substantial demand on fabrication
and characterization techniques. Colloid and polymer science
offer methods to create novel materials that possess periodic
variations of density and elastic properties at length scales
commensurate with the wave length of hypersonic phonons
and hence visible photons. The key quantity is the dispersion
ω(q) of high frequency (GHz) acoustic excitations with
wave vector q which is measured by the noninvasive high-
resolution Brillouin light scattering. The approach involves
the exploitation of Bragg-type bandgaps (BGs) that result
from the destructive interference of waves in periodic media.
However, the sensitivity of BG formation to structural
disorder limits the application of self-assembly methods that
are susceptible to defect formation. Hybridization gaps (HG),
originating from the anti-crossing between local resonant
and propagating modes, are robust to structural disorder and
occur at wavelengths much larger than the size of the resonant
unit. Here, examples based on hierarchical structures will
be highlighted: (i) 1D-hPnC to acquire comprehensive
understanding, while the incorporation of defects holds
a wealth of opportunities to engineer ω(q). (ii) In colloid
based phononics, ω(q) has revealed both types of band gabs.
(iii) particle brush materials with controlled architecture
of the grafted chains enable a new strategy to realize HG’s
(iv) Hierarchically nanostructured matter can involve
unprecedented phonon phono propagation mechanisms.
J Biotech and Phyto 2017