Phononic crystals, i.e. 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. Realizing these opportunities requires strategies to deliberately ‘engineer’ the phononic band structure of materials in the frequency range of interest. Phononic crystals, the acoustic equivalents of the photonic crystals, are controlled by a larger number of material parameters, as phonon cannot propagate in vacuum. The study of hypersonic phononic crystals (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 mesoscopic length scales commensurate with the wave length of hypersonic phonons and hence photons of the visible light. The key quantity is the dispersion ω(k) of high frequency (GHz) acoustic excitations with wave vector k which is measured by the noninvasive high resolution spontaneous Brillouin light scattering. (Nano Lett 2012; Phys.Rev.Lett.2013). Few characteristic examples of colloid-based 3D-hPnC and a nature hierarchically nanostructured material (spider and silk worm fibers) will be highlighted (Nat.Mater. 2006; Nat.Comm. 2015, Nat. Mater. 2016)). At the end a novel application of the particle vibration spectroscopy to directly observe the free surface mobile layers in polymer colloids as well as their glass transition and elasticity will be presented (Nat.Comm.2018)
George Fytas is professor of Physical Chemistry in the Department of Materials Science & Technology of the University of Crete, affiliated member of IESL/FORTH and External Member of the Max Planck Institute for Polymer Research in Mainz. George Fytas has received the BS in Chemistry Department of the University of Athens and the PhD with from the Technical University of Hannover in Germany. He performed his postdoc research in SUNY at Stony Brook in USA and received his habilitation from the University of Bielefeld in Germany. George Fytas trained 31 PhD students and 14 postdocs who all have successful carriers worldwide. He published over 270 peer reviewed scientific articles (Science, Nature (Materials,-Nanotechnology,-Chemistry,-Communications), Nanoletters, Angewandte Chemie JACS, ACS Nano, Adv. Mater, PRL), one edited book and 10 reviews in books. His published work has received more than 9100 citations (HI: 48).
He has received honor professorship offer from the University of Patras and the first FO.R.T.H Award for Basic Research (1999). He was nominated as external member of Max Planck Society (1998), received a Humboldt Senior Research Award (2002), became a Fellow of the American Physical Society (2004), received an invited professorship in the University of Lille (2009, 2012) is Member of the Institute for Complex Molecular Systems ICMS (TU/e), Eindhoven, Adjunct Professor at the University of Akron (2013), and distinguished Fellow of Tongji University in Shanghai, and awarded with ERC 2015 Advanced Grant. He served as Regional Editor of Colloid & Polymer Science and member of the Editorial Advisory Board in four international journals. His mission is the basic understanding and prediction of the behavior and tunability of unconventional physical properties of structured soft materials with spatiotemporal complexity.