Simplifying Microfluidic Flow Control

Published on behalf of Kathryn Mayer, web writer for Lab on a Chip

New research shows that it is possible to carry out flow switching in microfluidic devices via a single active hardware element: a tunable frequency periodic pressure source.

A common hindrance to the design of microfluidic systems is the large amount of unwieldy and expensive hardware (valves, actuators, etc.) required to control fluid flow rates in different parts of the chip. A team of engineers and chemists from UC Santa Barbara, the University of Virginia, and the University of Southampton has devised a method to address this problem. In the new method, a single variable-frequency pressure source communicates with the microfluidic chip via tubes connected to deformable films (“capacitors”) on the chip. The length of each tube is chosen such that the tubes will have well-separated resonance frequencies. Then, the frequency of the actuator is tuned to drive fluid flow in the desired channel only.

As demonstrated in their recent paper, the authors produced three separate devices with clearly differentiated excitation frequencies (see figure below). In addition, they demonstrated a single device with two separate flow channels that could be switched between by modulation of the driving frequency.

Fluid flow in the chip (left, from Figure 1E) is controlled by a periodic pressure source connected to a deformable film by a tube. By using tubes of different lengths, one can selectively drive fluid flow in a channel by tuning the pressure source to that channel’s resonant frequency (right, from Figure 2A).

Fluid flow in the chip (left, from Figure 1E) is controlled by a periodic pressure source connected to a deformable film by a tube. By using tubes of different lengths, one can selectively drive fluid flow in a channel by tuning the pressure source to that channel’s resonant frequency (right, from Figure 2A).

The authors state that by utilizing a large range of excitation frequencies it should be possible to independently control up to 10 flow channels on a single chip using their technique. They also project that it should be possible to control multiple channels simultaneously by employing an excitation signal incorporating multiple frequencies. Thus, this new flow control technique has the potential to be an elegant and low-cost solution for many types of diagnostic applications.

Read this article in Lab on a Chip today:

Flow switching in microfluidic networks using passive features and frequency tuning
Rachel R. Collino, Neil Reilly-Shapiro, Bryant Foresman, Kerui Xu, Marcel Utz, James P. Landers, and Matthew R. Begley
DOI: 10.1039/c3lc50481f

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