Article abstract
Nature Materials 5, 830 - 836 (2006)
doi:10.1038/nmat1727
Subject Categories: Colloids | Polymers | Nanoscale materials
Observation and tuning of hypersonic bandgaps in colloidal crystals
Wei Cheng1, Jianjun Wang1, Ulrich Jonas1, George Fytas1,2 and Nikolaos Stefanou3
Abstract
Composite materials with periodic variations of density and/or sound velocities, so-called phononic crystals, can exhibit bandgaps where propagation of acoustic waves is forbidden. Phononic crystals are the elastic analogue of the well-established photonic crystals and show potential for manipulating the flow of elastic energy. So far, the experimental realization of phononic crystals has been restricted to macroscopic systems with sonic or ultrasonic bandgaps in the sub-MHz frequency range. In this work, using high-resolution Brillouin spectroscopy we report the first observation of a hypersonic bandgap in face-centred-cubic colloidal crystals formed by self-assembly of polystyrene nanoparticles with subsequent fluid infiltration. Depending on the particle size and the sound velocity in the infiltrated fluid, the frequency and the width of the gap can be tuned. Promising technological applications of hypersonic crystals, ranging from tunable filters and heat management to acousto-optical devices, are anticipated.
- Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
- Department of Materials Science and Technology and FORTH, 71110 Heraklion, Greece
- Section of Solid State Physics, University of Athens, 15784 Athens, Greece
Correspondence to: George Fytas1,2 e-mail: fytas@mpip-mainz.mpg.de
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