title: Anisotropic lattice expansion of three-dimensional colloidal crystals and its impact on hypersonic phonon band gaps.
abstract: We report anisotropic expansion of self-assembled colloidal polystyrene-poly(dimethylsiloxane) crystals and its impact on the phonon band structure at hypersonic frequencies. The structural expansion was achieved by a multistep infiltration-polymerization process. Such a process expands the interplanar lattice distance 17% after 8 cycles whereas the in-plane distance remains unaffected. The variation of hypersonic phonon band structure induced by the anisotropic lattice expansion was recorded by Brillouin measurements. In the sample before expansion, a phononic band gap between 3.7 and 4.4 GHz is observed; after 17% structural expansion, the gap is shifted to a lower frequency between 3.5 and 4.0 GHz. This study offers a facile approach to control the macroscopic structure of colloidal crystals with great potential in designing tunable phononic devices.
authors.affiliation: Toyota Research Institute of North America, Toyota Motor Engineering and Manufacturing North America, Inc., Ann Arbor, Michigan 48105, USA. chen.ling@tema.toyota.com.
authors.forename: Songtao
authors.initials: S
authors.lastname: Wu
authors.forename: Gaohua
authors.initials: G
authors.lastname: Zhu
authors.forename: Jin S
authors.initials: JS
authors.lastname: Zhang
authors.forename: Debasish
authors.initials: D
authors.lastname: Banerjee
authors.forename: Jay D
authors.initials: JD
authors.lastname: Bass
authors.forename: Chen
authors.initials: C
authors.lastname: Ling
authors.forename: Kazuhisa
authors.initials: K
authors.lastname: Yano