Biomedical Sensors and Subsystems

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Dynamic Control of Nanoliter Droplet Volume and Composition
Ramsey Zeitoun, Marcus Goudie, and Mark A. Burns
Droplet ethanol concentration response to changing conditions in side channels
Droplet ethanol concentration response to changing conditions in side channels

Nanoliter droplets in microfluidic devices can be used to perform thousands of controlled and independent chemical and biological experiments while minimizing reagents, cost and time. However, the absence of simple and versatile methods capable of controlling the contents of these nanoliter chemical systems limits their scientific potential. To address this, we have developed a simple method to continuously control nanoliter chemical systems by integrating a time-resolved convective flow signal across a permeable membrane wall. With this method, we can independently control the volume and concentration of nanoliter-sized drops without ever directly contacting the fluid. We achieved fluid introduction and removal rates ranging from .23 to 4.0 pL/s. Furthermore, we expanded this method to perform chemical processes. We precipitated silver chloride using a flow signal of sodium chloride and silver nitrate droplets. From there, we were able to separate sodium chloride reactants with a water flow signal and dissolve silver chloride solids with an ammonia hydroxide flow signal.

Updated 06/13/2011