Shape-sensitive crystallization in colloidal superball fluids

Laura Rossi, Vishal Soni, Douglas J. Ashton, David J. Pine, Albert P. Philipse, Paul M. Chaikin, Marjolein Dijkstra, Stefano Sacanna, William T M Irvine

Research output: Contribution to journalArticlepeer-review


Guiding the self-assembly of materials by controlling the shape of the individual particle constituents is a powerful approach to material design. We show that colloidal silica superballs crystallize into canted phases in the presence of depletants. Some of these phases are consistent with the so-called "Λ1" lattice that was recently predicted as the densest packing of superdisks. As the size of the depletant is reduced, however, we observe a transition to a square phase. The differences in these entropically stabilized phases result from an interplay between the size of the depletants and the fine structure of the superball shape. We find qualitative agreement of our experimental results both with a phase diagram computed on the basis of the volume accessible to the depletants and with simulations. By using a mixture of depletants, one of which is thermosensitive, we induce solid-to-solid phase transitions between square and canted structures. The use of depletant size to leverage fine features of the shape of particles in driving their self-assembly demonstrates a general and powerful mechanism for engineering novel materials.

Original languageEnglish (US)
Pages (from-to)5286-5290
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number17
StatePublished - Apr 28 2015


  • Dense packings
  • Depletion interactions
  • Monte Carlo simulations
  • Phase behavior
  • Superballs

ASJC Scopus subject areas

  • General


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