Immobilization/encapsulation of cells using electrostatic droplet generation - Experiments and theory

Abstract

The mechanism of alginate droplet formation as well as experimental parameters for producing very small polymer microbeads (i,e, less then 100 microns diameter) using an electrostatic droplet generator were investigated, It was found that microbead size was a function of needle diameter, charge arrangement (i,e, electrode geometry and spacing) and strength of electric field. The process of alginate droplet formation under the influence of electrostatic forces was assessed with an image analysis/video system and revealed distinct stages; After a voltage was applied the liquid meniscus at the needle tip was distorted from a spherical shape into an inverted cone-like shape. Alginate solution flowed into this cone at an increasing rate causing formation of a neck-like filament, When this filament broke away, producing small droplets, the meniscus relaxed back to a spherical shape until now of the polymer caused the process to start again, A mathematical model of droplet formation at the electrified needle was developed from an analysis of the forces acting on a charged droplet, and agreed well with experimental results. Finally, to assess the effect of an electric field on animal cell viability, an insect cell suspension was subjected to a high voltage, There was no detectable loss in cell viability after the voltage was applied.