The microfluidic cell culture area is depicted in figure 2. The cells are loaded in a large (1mm x 3mm) rectangular trapping area. This region consists of three 1mm x 1mm trapping pads of progressively smaller ceiling heights for optimized loading of cells (4-6 micron for haploid, 5-8 for diploid). After loading, cells are held firmly in place by the elastomeric ceiling (see figures 5-7).

Nine (3x3) position markers are incorporated into each trap area to facilitate image navigation. Each marker has a missing dot at the location corresponding to the global position in the array and a "I" or "II" mark to indicate unit number.

A key feature of the Y2 design is the ability to change the solution exposed to the cells in real time. After switching the flow on the control panel, the solution in the cell trapping area will completely turn over as reported in Figure 4. Because of the highly laminar flow profile, a sharp boundary interface between the two solutions will "sweep" across the chamber without forming a mixing gradient. Cells closer to the flow inlets will experience proportionately faster exchange rates.

The carefully designed microfluidic network ensures rapid laminar flow exchange, continuous flows for over 3 days without refilling, and elimination of cross-flows between the exposure channels.

Temperature shift experiments can be conducted when used in conjunction with the ONIX-TCC Temperature Controller.

Figure 5 S. cerevisiae in the microfluidic device

Courtesy of the Lim Lab, UCSF

Figure 6 S. pombe in the microfluidic device

Courtesy of the Forsburg Lab, USC

Figure 7 Schematic of cell trapping mechanism