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Shaping Microscale Flows with Electric Fields

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The miniaturization of transistors from vacuum tubes to microchips has enabled the transformation of computers from machines filling rooms to the pocket-sized devices we know today. Similarly, the field of lab-on-a-chip seeks to revolutionize chemical and biological analysis by reducing large scale laboratories to the size of a microfluidic chip.

Although the concept of lab-on-a-chip was suggested more than 30 years ago, existing microfluidic systems are still far from achieving that vision. This is largely due to the fact that current microfluidic chips are mainly composed of channels carved into rigid substrates, such as polymers or glass, allowing implementation of only a very specific function for which it was designed. Any sequence of operation must be predesigned and hard written onto the chip – far from the versatility and configurability expected from a true lab-on-a-chip system.

In collaboration with scientists at Technion – Israel Institute of Technology, our team at IBM Research – Zurich is breaking this paradigm. Together, we have now demonstrated a new mechanism by which “virtual channels” guiding liquid along a desired paths are created using solely electric fields. These flow patterns can be controlled electronically, allowing configuration and reconfiguration on demand. This work was published online on May 6 in the Proceedings of the National Academy of Sciences.

Fig. 1: Individual electrodes create dipole-like flows. Superposition of such dipoles enables the creation of complex, nearly arbitrary, flow fields.

Fig. 1: Individual electrodes create dipole-like flows. Superposition of such dipoles enables the creation of complex, nearly arbitrary, flow fields.

When an electric field acts on charges near a surface, it moves that charge and drags the liquid along with it. By using an array of electrodes at the bottom of a microfluidics chamber and controlling their charges, we essentially set up an array of conveyor belts whose directions and intensities can be controlled electronically.

Fig. 2: By changing the potential distribution over an array of electrodes, streamlines in the flow can be dynamically manipulated.

Fig. 2: By changing the potential distribution over an array of electrodes, streamlines in the flow can be dynamically manipulated.

Our team showed the ability to establish a variety of flows and switch from one to another in real time. Because we are affecting the flow from within, we can also create flows that are not achievable with conventional means like pressure pumps. For example, we can mix specific regions without disturbing the liquid around them, or alternatively we can create regions where the liquid is still while there is flow all around them.

We strongly believe that this is the beginning of a new trajectory for lab-on-a-chip, where truly configurable systems could be implemented.

Editor’s note: This work is part of a multi-year collaboration between the teams of Govind Kaigala at IBM Research – Zurich and Moran Bercovici at Technion and was funded by the European Union FP7 funding (Virtual Vials) and by the European Research Council (MetamorphChip).

Postdoctoral Researcher

Govind Kaigala

Research Staff Member

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