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Controlling Chirality of Entropic Crystals
Pablo F Damasceno1,2, Andrew S Karas2,3, Benjamin A Schultz2,4
1Applied Physics Program, University of Michigan, Ann Arbor, Michigan 48109, USA.
Physical Review Letters
|November 10, 2015
Summary
Researchers achieved control over homochiral colloidal crystal formation using chiral polyhedra. Tuning entropic forces enabled selective assembly of desired crystal handedness for photonic metamaterials.
Area of Science:
- Colloid science
- Materials science
- Crystallography
Background:
- Colloidal crystals offer complex structures comparable to atomic crystals, driven by entropy maximization.
- Homochiral colloidal crystals, crucial for photonic metamaterials, have remained elusive.
- Existing methods lack precise control over the handedness of self-assembled chiral crystals.
Purpose of the Study:
- To investigate the self-assembly of chiral polyhedra into colloidal crystals.
- To achieve controlled formation of homochiral colloidal crystals.
- To understand the relationship between particle chirality and crystal handedness.
Main Methods:
- Utilized Monte Carlo simulations to model the self-assembly process.
- Employed chiral polyhedra with varying degrees of faceting.
- Investigated the influence of directional entropic forces on crystal formation.
- Quantified particle chirality using geometric analysis and potential of mean force/torque diagrams.
Main Results:
- Chiral polyhedra with weak directional forces assembled into either achiral or randomly-handed chiral crystals.
- Particles with stronger faceting demonstrated higher selectivity, forming chiral crystals with handedness dictated by particle chirality.
- Adjusting entropic forces (via particle rounding or depletants) allowed switching between achiral and homochiral crystal structures.
Conclusions:
- Particle geometry and entropic forces are key determinants in self-assembling homochiral colloidal crystals.
- Stronger faceting in building blocks enables predictable control over crystal handedness.
- This work provides a pathway for designing and fabricating chiral colloidal crystals for advanced applications like photonic metamaterials.
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