Figure 2.

Side view of the three-channel microfluidic device used to expose cells to constant chemoattractant gradients. The channels, fabricated in solute-impermeable polydimethylsiloxane, were 20-mm long, 100-μm deep, and 600-μm wide, with 400-μm spacing between each channel. The agarose layer was 0.5-mm thick. Motility medium with a constant maltose concentration was flowed through the left outer channel, and motility medium with a constant MeAsp concentration was flowed through the right outer channel. For the opposing-gradient experiments, both the maltose and MeAsp concentrations were nonzero; for the single-gradient experiments, one of the two outer channels contained only motility medium. The chemoattractants diffused through the agarose layer and up into the test channel, creating two steady linear concentration profiles in opposite directions. This figure was adapted from (46). To see this figure in color, go online.