Microfabricated ratchet structure integrated concentrator arrays for synthetic bacterial cell-to-cell communication assays.

We describe a microfluidic concentrator array device that is integrated with microfabricated ratchet structures to concentrate motile bacterial cells in desired destinations with required cell densities. The device consists of many pairs of concentrators with a wide range of spacing distances on a chip, and allows cells in one concentrator to be physically separated from but chemically connected to cells in the other concentrator. Therefore, the device facilitates quantification of the effect of spacing distance on the cell-to-cell communication of synthetically engineered bacterial cells. In addition, the device enables us to control the cell number density in each concentrator unit by adjusting the concentration time and the density of cell suspensions, and the basic concentrator unit of the device can be repeatedly duplicated on a chip. Hence, the device not only facilitates an investigation of the effect of cell densities on cell-to-cell communication, but it can also be further applied to an investigation of cellular communication among multiple types of cells. Lastly, the device can be easily fabricated using a single-layered soft-lithography technology so that we believe it would provide a simple but robust means for many synthetic and systems biologists to simplify and speed up their investigations of the synthetic genetic circuits in bacterial cells.