Reversible solid-state phase transitions in confined two-layer colloidal crystals

Zhuoqiang Jia, Mena Youssef, Alexandra Samper, Stefano Sacanna, Stephanie S. Lee

Research output: Contribution to journalArticlepeer-review


Using a combination of fluorescence and bright-field optical imaging, the solid-state packing structures of semi-confined two-layer spherical colloidal crystals were observed during modulation of an external AC electric field. Upon increasing field strength, the bottom layer of colloids (layer 1) transitioned from the entropically favored hexagonal packing structure with p6m symmetry to a square-packing structure with p4m symmetry. The packing structure of layer 2 was determined by the packing structure of layer 1, with layer 2 particles resting in, and moving in registry with, the low-energy interstitial sites of layer 1. Modulation of the field strength thus resulted in a reversible transition between a face-centered cubic crystal structure and a body-centered cubic crystal structure at low and high field strengths, respectively. These structures were found to be sensitive to the particle density in the wells, with vacancies and insertions leading to the formation of mixed crystal phases at high field strengths. [Figure not available: see fulltext.]

Original languageEnglish (US)
Pages (from-to)1611-1617
Number of pages7
JournalColloid and Polymer Science
Issue number12
StatePublished - Dec 2020


  • Colloidal crystal
  • Negative dielectrophoresis
  • Phase diagram
  • Reversible assembly
  • Solid-state phase transition

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Polymers and Plastics
  • Colloid and Surface Chemistry
  • Materials Chemistry


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