Microfluidics Woven into Fibers Have Potential for New Devices

Microfluidics have been woven into fibers by researchers at MIT to allow for more complex medical-testing devices.

Researchers at MIT have incorporated microfluidics into individual fibers, making it possible to process higher volumes of fluid in more complex ways. In doing so, they have enabled diverse new applications—especially for the medical-testing field.

A multidisciplinary team of electrical engineers, materials scientists, and microsystems technologists has discovered a way to solve a challenge with microfluidics devices that could only allow for them to be used on a tiny scale. They therefore extended their range of use, as described in an MIT news release.

microfluid fibers
An illustration shows how researchers at MIT are integrating conductive wires along with microfluidic channels in long fibers, demonstrating the ability to sort cells—separating living cells from dead ones, because the cells respond differently to an electric field. The live cells, shown in green, are pulled toward the outside edge of the channels, while the dead cells (red) are pulled toward the center, allowing them to be sent into separate channels. (Image source: MIT)

Microscopic Channels

Microfluidics devices are very small systems with microscopic channels that can be used for chemical or biomedical testing and research, such as for processing tiny droplets of blood for testing. Typically, these devices are manufactured onto microchip-like structures to provide a way of mixing, separating, and testing fluids in microscopic volumes.

Until now, they haven’t been very useful for procedures that need larger volumes of liquid to detect substances present in minute amounts. However, the work out of MIT changes this, ushering in a new “macro” approach to microfluidics, researchers said in the news release. The work also expands the size and shape in which microfluidic devices can be created, said MIT graduate student Rodger Yuan, one of the main researchers on the project.

Currently, microfluidic devices are limited to the size of the silicon wafers used in such systems, which also limits the shapes of the channels through which the liquid flows. “Over the last 20 years, the majority of microfluidic research has been done in a chip format because microfabrication methods are very good at making high-precision channels in complex arrangements,” Yuan told Design News.

Right now, they can only have square or rectangular cross sections, he said. “Silicon chip technology is really good at making rectangular profiles, but anything beyond that requires really specialized techniques,” Yuan said. “They can make triangles, but only with certain specific angles.”

A New Method

The new fiber-based method developed by Yuan and his team changes this by allowing for a variety of cross-sectional shapes for the channels to be implemented—including star, cross, or bowtie shapes. Particular applications, such as those that need to automatically sort different types of cells in a biological sample, could find these new shapes quite useful, Yuan said. “Here, we introduce a new way to do microfluidics in a fiber format that offers many advantages over the traditional chip-based format,” he said.

Researchers developed the fibers using an oversized polymer cylinder called a preform. It contains the exact shape and materials desired for the final fiber, but in much larger form. This makes it much easier for researchers to make them in very precise configurations.

Scientists heated the preform and loaded it into a drop tower. There, it was pulled through a nozzle to constrict it to a narrow fiber that’s one-fortieth the diameter of the preform, preserving all internal shapes and arrangements.

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