Non-Invasive Sorting of Lipid Producing Microalgae With Dielectrophoresis Using Microelectrodes

Abstract

In order to advance the algae biofuel industry, we are constructing a dielectrophoretic, single-cell sorter that selects algae based on lipid content. This tool can lower production costs by aiding in strain selection, online culture monitoring, or directed evolution studies. Dielectrophoresis (DEP) is the polarization of particles or cells in a non-uniform electric field, which leads to a Coulomb force on the cell. Lipids and cell cytoplasm have vastly different dielectric properties. Therefore, as a cell accumulates lipid, we predict a change in the overall DEP response. Our models show that in algae culture medium, we should be able to distinguish between high and low lipid content cells at frequencies above 100 MHz. This was confirmed by experiments, in which high and low lipid cultures of Neochloris oleoabundans have DEP crossover frequencies of 190 MHz and 125 MHz, respectively. We have also fabricated a proof-of-concept device validating that cells can be manipulated under DEP. However, in order to achieve sorting, we will require higher frequencies as well as a modified design to eliminate non-uniformities in the electric field through the channel height.