In this video, we see magnetically labeled circulating tumor cells (shown as yellow spheres), together with red, white and platelet cells, attempting to travel over an array of slanted ramps. The ramps act as speed bumps, slowing the tumor cells. As the tumor cells slow, the flow carries them along the length of the ramp, causing lateral displacement. After the tumor cells traverse an array of these ramps, they have sufficiently been displaced and can be continuously isolated from other cells in the sample.
In the May 25 online issue of Physical Review Letters, German Drazer, an assistant professor of chemical and biomolecular engineering at Johns Hopkins University and his doctoral student, Jorge A. Bernate, reported that they have developed a lab-on-chip platform, also known as a microfluidic device, that can sort particles, cells or other tiny matter by physical means such as gravity. By moving a liquid over 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, the team reported.
Animation by Martin Rietveld, Johns Hopkins University, Institute for NanoBioTechnology. Narration: Mustapha Jamal, Johns Hopkins University, Department of Chemical and Biomolecular Engineering.