### Abstract

Two-dimensional colloidal crystals confined within electric field traps on the surface of a dielectrophoretic cell undergo reversible phase transitions that depend on the strength of the applied AC electric field. At low field strengths, the particles adopt a two-dimensional hexagonal close-packed lattice with p6m plane group symmetry and the maximum achievable packing fraction of φ = 0.91. Higher electric field strengths induce dipoles in the particles that provoke a phase transition to structures that depend on the number of particles confined in the trap. Whereas traps containing N = 24 particles transform to a square-packed lattice with p4m symmetry and φ = 0.79 is observed, traps of the same size containing N = 23 particles can also pack in a lattice with p2 symmetry and φ = 0.66. Traps with N = 21, 22, and 25 particles exhibit a mixture of packing structures, revealing the influence of lateral compressive forces, in addition to induced dipole interactions, in stabilizing loosely packed arrangements. These observations permit construction of a phase diagram based on adjustable parameters of electric field strength (0-750 V/cm) and particle number (N = 21-25).

Original language | English (US) |
---|---|

Pages (from-to) | 10411-10417 |

Number of pages | 7 |

Journal | Langmuir |

Volume | 31 |

Issue number | 38 |

DOIs | |

State | Published - Sep 29 2015 |

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### ASJC Scopus subject areas

- Electrochemistry
- Condensed Matter Physics
- Surfaces and Interfaces
- Materials Science(all)
- Spectroscopy

### Cite this

*Langmuir*,

*31*(38), 10411-10417. https://doi.org/10.1021/acs.langmuir.5b03230

**Electric-Field-Induced Reversible Phase Transitions in Two-Dimensional Colloidal Crystals.** / Collins, Kelsey A.; Zhong, Xiao; Song, Pengcheng; Little, Neva R.; Ward, Michael; Lee, Stephanie S.

Research output: Contribution to journal › Article

*Langmuir*, vol. 31, no. 38, pp. 10411-10417. https://doi.org/10.1021/acs.langmuir.5b03230

}

TY - JOUR

T1 - Electric-Field-Induced Reversible Phase Transitions in Two-Dimensional Colloidal Crystals

AU - Collins, Kelsey A.

AU - Zhong, Xiao

AU - Song, Pengcheng

AU - Little, Neva R.

AU - Ward, Michael

AU - Lee, Stephanie S.

PY - 2015/9/29

Y1 - 2015/9/29

N2 - Two-dimensional colloidal crystals confined within electric field traps on the surface of a dielectrophoretic cell undergo reversible phase transitions that depend on the strength of the applied AC electric field. At low field strengths, the particles adopt a two-dimensional hexagonal close-packed lattice with p6m plane group symmetry and the maximum achievable packing fraction of φ = 0.91. Higher electric field strengths induce dipoles in the particles that provoke a phase transition to structures that depend on the number of particles confined in the trap. Whereas traps containing N = 24 particles transform to a square-packed lattice with p4m symmetry and φ = 0.79 is observed, traps of the same size containing N = 23 particles can also pack in a lattice with p2 symmetry and φ = 0.66. Traps with N = 21, 22, and 25 particles exhibit a mixture of packing structures, revealing the influence of lateral compressive forces, in addition to induced dipole interactions, in stabilizing loosely packed arrangements. These observations permit construction of a phase diagram based on adjustable parameters of electric field strength (0-750 V/cm) and particle number (N = 21-25).

AB - Two-dimensional colloidal crystals confined within electric field traps on the surface of a dielectrophoretic cell undergo reversible phase transitions that depend on the strength of the applied AC electric field. At low field strengths, the particles adopt a two-dimensional hexagonal close-packed lattice with p6m plane group symmetry and the maximum achievable packing fraction of φ = 0.91. Higher electric field strengths induce dipoles in the particles that provoke a phase transition to structures that depend on the number of particles confined in the trap. Whereas traps containing N = 24 particles transform to a square-packed lattice with p4m symmetry and φ = 0.79 is observed, traps of the same size containing N = 23 particles can also pack in a lattice with p2 symmetry and φ = 0.66. Traps with N = 21, 22, and 25 particles exhibit a mixture of packing structures, revealing the influence of lateral compressive forces, in addition to induced dipole interactions, in stabilizing loosely packed arrangements. These observations permit construction of a phase diagram based on adjustable parameters of electric field strength (0-750 V/cm) and particle number (N = 21-25).

UR - http://www.scopus.com/inward/record.url?scp=84942783574&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84942783574&partnerID=8YFLogxK

U2 - 10.1021/acs.langmuir.5b03230

DO - 10.1021/acs.langmuir.5b03230

M3 - Article

AN - SCOPUS:84942783574

VL - 31

SP - 10411

EP - 10417

JO - Langmuir

JF - Langmuir

SN - 0743-7463

IS - 38

ER -