Droplet Solution Exchange Platform Utilizing Dielectrophoretic Force

This paper presents an in-droplet solution exchange technology for water-in-oil emulsion droplet-based cellular assay systems. Changing out solution in which cells are suspended in within a water-in-oil emulsion droplet is challenging. Here, dielectrophoresis-based cell manipulation technique has been utilized to move all cells within a water-in-oil emulsion droplet to one side of the droplet, followed by asymmetric droplet splitting to obtain a small water-in-oil emulsion droplet with high concentration of cells within. By merging this droplet with a new droplet that contains the desired solution results in the solution in which cells are suspended in to be replaced on chip. To demonstrate the functionality of this system, the microalgal strain Chlamydomonas reinhardtii (C. reinhardtii) was successfully used. This technology enables conducting essentially a centrifugation step, one of the most commonly used steps in any cellular assays, to be performed in the water-in-oil droplet format.