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The lab-on-chip platform, also known as a microfluidic device, is powered in its simplest form by gravity, though other forces like magnetism can also be used.

By pouring a liquid, like blood, past a series of micron-scale-high diagonal ramps—similar to speed bumps on a road—the device causes microscopic material to separate into discrete categories, based on weight, size, or other factors.

German Drazer, assistant professor of chemical and biomolecular engineering at Johns Hopkins University, and graduate student Jorge A. Bernate reported their results in the May 25 online issue of Physical Review Letters.

“The ultimate goal is to develop a simple device that can be used in routine checkups by health care providers,” says Bernate, lead author on the paper. “It could be used to detect the handful of circulating tumor cells that have managed to survive among billions of normal blood cells.”

Ideally, these cancer cells in the bloodstream would be detected and targeted for treatment before they’ve had a chance to metastasize, or spread cancer elsewhere in the body, Bernate says. Detection at early stages of cancer is critical for successful treatment.

How does this sorting process occur? Inside the microfluidic device, particles and cells suspended in a liquid can flow along a “highway” that has speed-bump-like obstacles. The bumps are positioned diagonally, instead of perpendicular to the path of the liquid and differ in height, depending on the application.

“As different particles are driven over these diagonal speed bumps, heavier ones have a harder time getting over than the lighter ones,” Bernate says.

When the particles cannot get over the ramp, they change course and travel diagonally along the length of the obstacle. As the process continues, particles end up fanning out in different directions.

“After the particles cross this section of the ‘highway,’” Bernate says, “they end up in different ‘lanes’ and can take different ‘exits,’ which allows for their continuous separation.”

Gravity is not the only way to slow down and sort particles as they attempt to traverse the speed bumps.

“Particles with an electrical charge or that are magnetic may also find it hard to go up over the obstacles in the presence of an electric or magnetic field,” Bernate says. For example, cancer cells could be weighted down with magnetic beads and then sorted in a device with a magnetic field.

The ability to sort and separate things at the micro- and nanoscale is important in many industries, ranging from solar power to bio-security. But a medical application is likely to be the most promising immediate use for the device.

Bernate is scheduled to complete his doctoral studies this summer. Until then, he will continue to collaborate with researchers at Johns Hopkins and with colleagues at InterUniversity Microelectronics Center in Belgium.

The research described in the journal article eventually led Bernate down the path at IMEC to develop a device that can easily sort whole blood into its components. A provisional patent has been filed for the device.

The research was funded in part by the National Science Foundation and the National Institutes of Health.

More news from Johns Hopkins University: http://releases.jhu.edu/