Formation and Motion Analysis of Colloidal Particle Chains Under an AC Electric Field

Research on formation and motion of colloidal chains under an AC electric field is being conducted to develop micro-robotic technology that can potentially be used in drug delivery, micro-surgery, and active sensors. The ultimate goal is to understand the formation of colloidal chains, characterize them, and probe the fundamental mechanisms of chain propulsion under AC electric fields. A “Colloidal dispersion” consists of the solvent and Latex particles suspended in the solvent. Colloidal particles range in size from a few nanometers to a few micrometers. When present under a parallel electric or magnetic field, the particles gain induced-dipoles similar to a bar magnet. Dipolar interactions between particles make them attract towards each other forming long chains in the direction of the applied field. The chains can be linked by polymer molecules (such as Polyvinylpyrrolidone) adsorbed on the particles. After chains have been formed, we can apply a perpendicular AC electric field. An electro-hydrodynamic (EHD) Flow will be induced surrounding the chain and possibly cause it to propel. This flow is caused by the movement of cations and anions in the solution being attracted to the oppositely charged electrodes. When there is an imbalanced EHD flow surrounding a chain, the fluid induces a force on the chain causing it to propel. When under the influence of this force, chains oscillate or propel just like a wiggling flagella as seen in cells. This preliminary research gave insight to how significant the motion and bond angles were in regards to non-propulsive and propulsive chains. Additionally, three procedures for forming and analyzing colloidal chains were developed. The first procedure allowed for the heating of the colloidal solution in a sealed environment while under the influence of an AC electric field. The second procedure allowed for the heating of this sealed environment while being viewed under a focal microscope. The 3rd procedure allowed for the production of 1 ml of colloidal chain solution.