A new method for making electrodes

Researchers from the University of North Carolina have developed a faster and simpler method for making microelectrodes used in microflow devices using liquid metal. Microflow devices use small amounts of liquid and have a wide range of applications, from testing tiny blood samples to performing advanced chemical research .

"We hope that by optimizing the integration of electrodes within microflow devices we can assist in the development and research of new technologies that utilize these devices as biomedical tools," says Dr. Michael Dickey, professor of chemical and biomolecular engineering at the University of North Carolina.

Typically, microfluidic devices contain solid metal electrodes that serve as sensors, pumps, and detectors. However, these solid electrodes may be problematic since they must be physically adapted to the channel that passes through the device. The channel serves as the point of departure for the fluid transported in the device. The physical fit of the electrodes is very challenging since their diameter is extremely tiny - only tens or hundreds of microns, the size of the canal itself.

The research team tackled solving this problem by designing microflow devices containing three channels, with the middle channel separated from the other two channels by a series of points close to each other. The researchers prepared the two outer channels by injecting a liquid metal alloy consisting of the metals gallium and indium. The alloy fills the outer channels completely, but it also creates an oxidized layer that widens the spacing between the dots and thus enables the receipt of an empty middle channel through which the various liquids flow.

"This approach makes it possible to obtain precisely arranged electrodes in a single step," notes the researcher. "The channels are built inside the device and thus the electrodes can be adjusted in advance - we make the metal reach exactly where we want it. This means faster and easier preparation of these devices."

In addition, the approach provides the possibility to prepare electrodes in useful configurations that could not be obtained with the previous methods, or this involved considerable effort. This can be done by changing the shape of the channels that will be created using the liquid metal. These configurations will be able to maintain more uniform electric fields that will be used in the treatment of liquids and particles. The research findings were published in the scientific journal Lab on a Chip.

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