Directed self-assembly of colloidal crystals by dielectrophoretic ordering

Area of Science:

• Colloid and Surface Science
• Electrokinetics
• Materials Self-Assembly

Background:

• Dielectrophoresis (DEP) is a technique used to manipulate particles using non-uniform electric fields.
• Understanding the factors influencing colloidal particle assembly is crucial for developing novel materials and devices.

Purpose of the Study:

• To investigate the dielectrophoretic assembly of colloidal particles.
• To determine the impact of particle size, charge, ionic strength, and electric field parameters on assembly kinetics and ordering.
• To validate electrokinetic models for predicting particle assembly.

Main Methods:

• Development and validation of a specialized dielectrophoresis (DEP) sample cell.
• Quantitative measurements using sequential light scattering and optical microscopy.
• Analysis of particle assembly kinetics and degree of ordering.

Main Results:

• Assembly kinetics and ordering are dependent on particle size, charge, ionic strength, and electric field strength/frequency.
• Established scaling for the order-disorder transition is confirmed and extended to higher frequencies.
• Particle electrophoretic mobility and order-disorder transition are accurately predicted by the standard electrokinetic model (SEKM).

Conclusions:

• The standard electrokinetic model (SEKM) effectively predicts colloidal particle assembly and electrophoretic mobility.
• An empirical scaling law combined with SEKM accurately predicts the order-disorder transition line over a wide range of particle sizes.
• Dielectrophoretic assembly offers a controllable method for directed self-assembly of colloidal particles.