<a href="http:&#x2F;&#x2F;www.biofilms.biz&#x2F;flow-cells" rel="nofollow">http:&#x2F;&#x2F;www.biofilms.biz&#x2F;flow-cells</a><p>basically they are little chambers with in ports and out ports with environmental control (temp, pressure).  You shove stuff in, let it react, then flow it back out.<p>Gives you control over concentrations.  The flow cell is transparent so you can put it in a microscope and analyze the reactions.  In this case it looks like they used beam lithography to create a surface inside the flow cell.