Darks from lights, dirty from clean. To sort microscopic particles and biological bits, biomolecular engineers are using gravity, physics, and speed bumps.
By moving the liquid over a series of tiny, micron-scale high diagonal ramps – like speed bumps on a road – the device causes microscopic materials to separate into discrete categories based on things like weight and size.
This microfluidic device – developed by German Drazer and Jorge Bernate of Johns Hopkins – could pick up the handful of circulating tumors cells that have managed to survive among billions of normal blood cells.
Detecting these cancer cells in the bloodstream could allow doctors to target them for treatment before they’ve had a chance to metastasize, or spread cancer elsewhere.
- Inside the device, particles and cells suspended in liquid flow along a highway with speed bumps and obstacles positioned diagonally to the path.
- As different particles are driven over these speed bumps, heavier ones have a harder time getting over than the lighter ones.
- When particles can’t get over the bump, they change course and travel diagonally along the length of the obstacle.
- As this continues, different particles end up fanning out in different directions. (They end up in different lanes and take different exits, which allows for their continuous separation.)
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. Cancer cells could be weighted down with magnetic beads and then sorted in a device with a magnetic field.
Watch a video of the micro-sorting device set to music. Magnetically labeled circulating tumor cells (pictured here as yellow spheres) travel with red and white blood cells and platelets. As the tumor cells slow, the flow carries them along the length of the slanted ramp, and after they’ve traversed an array of ramps, they’ll be displaced and continuously isolated from other cells.
The work was published in Physical Review Letters last month.
[Via JHU news]
Images: Martin Rietveld